法国专利FR3047811A1 MODULATOR OF PROPAGATION LOSSES AND OF THE PROPAGATION INDEX OF A GUIDE OPTICAL SIGNAL

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专利摘要:
This modulator (100) comprises: a first doped monocrystalline silicon electrode (120), this first electrode extending from a proximal end (12), a second electrode (130) made of doped III-V crystalline material, this second electrode extending from a proximal end (32), opposite the proximal end (12) of the first electrode (120), to a distal end (31), - an area (34) ) which extends: - in a direction perpendicular to the plane of the substrate, from the distal end (31) of the second electrode to a substrate (1, 2; 44; 552), and - in a transverse direction ( X) and in the direction (Y) of propagation of the optical signal, under the whole of the distal end (31) of the second electrode (130), this zone (34) consisting solely of one or more solid dielectric materials (20, 116).
公开号:FR3047811A1
申请号:FR1651138
申请日:2016-02-12
公开日:2017-08-18
发明作者:Sylvie Menezo
申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
IPC主号:

专利说明:

MODULATOR OF PROPAGATION LOSSES AND OF THE PROPAGATION INDEX OF A GUIDE OPTICAL SIGNAL
The invention relates to a modulator of the propagation losses and the propagation index of a guided optical signal and a transmitter comprising such a modulator. The invention also relates to a method of manufacturing this transmitter.
Loss of propagation refers to the optical losses seen by the optical mode propagating in a waveguide in which it is guided.
[003] Propagation index denotes the effective propagation index of the optical mode propagating in a waveguide in which it is guided.
Such known modulators comprise a waveguide formed by the stack immediately on one another: a proximal end of a first monocrystalline silicon electrode, a thin layer of dielectric material, and - a proximal end of a second electrode.
For example, such a modulator is described in the application US2009103850.
By applying a potential difference between the first and second electrodes, the density of charge carriers at the interfaces between the layer of dielectric material and the proximal ends of the first and second electrodes is modified. This induces a modification of the propagation losses and the propagation index seen by the guided optical field and propagating in the waveguide. Typically, the layer of dielectric material is a layer of silicon dioxide. It is very difficult to epitaxially grow a monocrystalline silicon layer on such a layer of silicon dioxide. Therefore, it has been proposed to make the second amorphous or polycrystalline silicon electrode. However, the use of an amorphous or polycrystalline silicon electrode increases the optical losses of the field, which is undesirable.
To overcome this drawback, the application WO2011 / 037686 proposes a manufacturing method that makes it possible to produce the second electrode of the monocrystalline silicon modulator, by bonding a monocrystalline silicon layer [008] The application US2015 / 0055910 proposes as for it to make the second electrode of crystalline material III-V such as InP, by direct bonding to the silicon of a layer of crystalline material III-V. The use of a crystalline material III-V to produce the second electrode must limit the optical losses compared to the case where it is made of amorphous or polycrystalline silicon.
[009] More precisely, the modulator described with reference to FIG. 2 of application US2015 / 0055910 comprises: a substrate extending mainly in a plane called "substrate plane" and a layer comprising monocrystalline silicon, extending directly on this substrate and mainly parallel to the plane of the substrate, - a first monocrystalline silicon doped P or N-structured silicon in the monocrystalline silicon of the layer comprising monocrystalline silicon, this first electrode extending in a transverse direction parallel to the plane of the substrate, from a proximal end to a distal end, and extending longitudinally in the direction of propagation of the optical signal; - a second electrode of doped crystalline material III-V having a doping of opposite sign to that of the first electrode, this second electrode extending in the transverse direction from an extremity proximal proximal end of the first electrode to a distal end on a side opposite to the distal end of the first electrode relative to an axis perpendicular to the plane of the substrate and extending therethrough the proximal ends, this second electrode extending longitudinally also in the direction of propagation of the optical signal, - a layer of dielectric material interposed between the proximal ends of the first and second electrodes to isolate them electrically from each other, - a first waveguide capable of guiding the optical signal to be modulated in the direction of propagation of the optical signal, this first waveguide being formed by the proximal ends of the electrodes and the portion of the layer of dielectric material interposed between these ends proximal, - contacting directly in mechanical and electrical contact with, respectively, the distal ends of the electrodes for electrically connecting the first and second electrodes to different electrical potentials so as to modify the density of charge carriers within the first waveguide, - an area which extends: - in the perpendicular to the plane of the substrate, from the distal end of the second electrode to the substrate, and in the transverse direction and in the direction of propagation of the optical signal, under the entire distal end of the second electrode.
In the application US2015 / 0055910, the zone which extends under the distal end of the second electrode to the substrate on which the monocrystalline silicon layer is deposited comprises a block (reference 116 in FIG. US2015 / 0055910) monocrystalline silicon isolated from the waveguide by an air block (reference 112 in Figure 2 of the application US2015 / 0055910).
By construction, in the modulator of the application US2015 / 0055910 or WO2011 / 037686 or US2009103850, the monocrystalline silicon thickness constituting the proximal end of the first electrode of the modulator must be equal to the total thickness of the monocrystalline silicon deposited on the substrate.
The invention described here aims to improve the modulator speed of the demand modulator US2015 / 0055910 while maintaining the advantage of low optical loss in the waveguide.
It therefore relates to such a modulator in which this zone, which extends under the distal end of the second electrode, is composed solely of one or more solid dielectric materials.
The modulator above retains the advantage of reduced losses of the demand modulator US2015 / 0055910. Indeed, one of the electrodes is monocrystalline silicon while the other electrode is made of crystalline material III-V.
In addition, the claimed modulator has no parasitic capacitance with respect to the modulator of the application US2015 / 0055910, which makes it possible to obtain a modulation speed much faster than that of the modulator of the application US2015 / 0055910. More specifically, it has been discovered that the distal end of the second electrode (reference 104 in FIG. 2 of US2015 / 0055910) of the US2015 / 0055910 demand modulator forms with the dielectric material layer (reference 118 in FIG. of application US2015 / 0055910) and a block (reference 116 in FIG. 2 of application US2015 / 0055910) of the monocrystalline silicon layer, a parasitic capacitance which greatly reduces the modulation speed of the modulator of the application US2015 / 0055910. Conversely, in the claimed modulator, the area below the distal end of the second electrode is only formed of a dielectric material so that the capacitance of the stray capacitor at that location is greatly reduced.
In general, the fact that the first electrode is encapsulated in the dielectric material also facilitates the manufacture of this modulator. For example, the error margins on the alignment of the electrodes facing each other can be quite significant because this misalignment does not create a significant parasitic capacitance in the case of the claimed modulator.
The embodiments of this modulator may include one or more of the following features: the maximum thickness of the proximal end of the first electrode is strictly less than the maximum thickness of the monocrystalline silicon of the layer comprising monocrystalline silicon ; the maximum thickness of the proximal end of the first electrode is between 0.7e32 and 1, 3e32, where e32 is the maximum thickness of the proximal end of the second electrode; the second electrode is made of InP or AsGa.
These embodiments of the modulator also have the following advantages: - The fact that the maximum thickness of the proximal end of the first electrode is strictly less than the maximum thickness of the single-crystal silicon of the layer comprising silicon monocrystalline, brings closer to the dielectric material layer, the point where is the maximum intensity of the optical field that propagates in the waveguide. By doing this, this point is brought closer to the zone where the density of the charge carriers is maximum when a potential difference is applied between the contacts of this modulator. This improves the efficiency of this modulator. Similarly, choosing the maximum thickness of the proximal end of the first electrode near the maximum thickness of the proximal end of the second electrode improves the efficiency of the modulator, particularly if the materials have roughly the same refractive indices, which is the case, for example, for ΓΙηΡ and silicon or AsGa and silicon. For example, refractive indices n1 and n2 are considered to be about the same if the index n1 is within the range [0.7n2; 1, 3n2] and preferably in the range [0.85n2; l, 15n2] or [0.95n2; 1, 05n2], [0019] The invention also relates to a photonic transmitter comprising: - a stack successively of a substrate extending mainly in a plane called "plane of the substrate", a layer comprising monocrystalline silicon encapsulated in a dielectric material and extending directly on this substrate, and a layer of dielectric material extending directly on the layer comprising monocrystalline silicon, these layers extending mainly parallel to the plane of the substrate, - a laser source semiconductor device capable of generating an optical signal, this laser source comprising a first waveguide of material III-V etched in a layer of gain material III-V, this layer of gain material III-V having a sub layer of doped crystalline material III-V extending directly on the layer of dielectric material; modulator of the propagation losses and the propagation index of a signal; guided optics realized on the same substrate and adapted to modulate the optical signal generated by the semiconductor laser source, wherein the modulator is according to any one of the preceding claims.
The embodiments of this transmitter may comprise one or more of the following features: the second electrode of this modulator is etched in the sub-layer of doped crystalline material III-V extending directly on the layer of dielectric material; the semiconductor laser source comprises a second waveguide made in the monocrystalline silicon of the layer comprising monocrystalline silicon and situated under the first waveguide of material III-V, this second waveguide being connected optically at the first waveguide of III-V material by evanescent or adiabatic coupling, and the maximum thickness of the proximal end of the first electrode is different from the maximum thickness of the second waveguide; the transmitter also comprises: a third waveguide capable of guiding the optical signal generated by the laser source and produced in the monocrystalline silicon of the layer comprising monocrystalline silicon; a device for tuning the phase of the optical signal which propagates in this third waveguide, this tuning device comprising: an arm made in the monocrystalline silicon of the layer comprising monocrystalline silicon and which extends in a transverse direction parallel to the plane of the substrate and perpendicular to the direction of propagation of the optical signal in the third waveguide, from a proximal end directly in mechanical contact with the third waveguide, to an N or P doped distal end, the minimum thickness of the end proximal of this arm in a direction perpendicular to the plane of the substrate being strictly less than the maximum thickness of the third waveguide d in the same direction, this arm also extending in the direction of propagation of the optical signal in the third waveguide, - making contact directly in mechanical and electrical contact with the distal end to circulate a current in this distal end adapted to heat the waveguide by thermal conduction through the arm.
These embodiments also have the following advantages: - The fact that the second electrode is made in the same sublayer of crystalline material III-V as that used for the realization of the waveguide material V of the laser source, greatly simplifies the manufacture of the transmitter. The fact that the thickness of the proximal end of the first electrode is different from the thickness of the monocrystalline silicon waveguide located under the waveguide made of a material III-V of the laser source makes it possible to improve both the operation of the laser source and the modulator. Indeed, to improve the operation of the laser source, it is desirable that the thickness of the waveguide located under the waveguide material III-V of this laser source is important. Conversely, to improve the operation of the modulator, it is desirable for the thickness of the proximal end of the first electrode to be approximately equal to the thickness of the proximal end of the second electrode. However, the thickness of the proximal end of the second electrode is generally smaller than the thickness of the waveguide located under the waveguide of material III-V. The use of a phase tuning device comprising a silicon arm whose distal end forms an electrical resistance made of doped silicon and whose proximal end is directly in mechanical contact with a silicon waveguide, allows to effectively heat this waveguide while limiting the propagation losses in this waveguide. Indeed, in this tuning device, the electrical resistance is remote from the waveguide and therefore does not increase the propagation losses in this waveguide. Thus, this tuning device is advantageous over known tuning devices comprising an electrical resistance obtained by doping a region of the waveguide or by producing an electrical resistance in the immediate vicinity of the waveguide. Indeed, in the latter two cases, the electrical resistance is located within an area where the intensity of the optical field of the propagating optical signal is important, which induces significant propagation losses.
The invention also relates to a manufacturing method of the claimed transmitter. This method comprises: - the realization, of a stack successively of a substrate extending mainly in a plane called "plane of the substrate", of a layer comprising monocrystalline silicon and extending directly on this substrate, and a layer of dielectric material extending directly on the layer comprising monocrystalline silicon, these layers extending mainly parallel to the plane of the substrate, - the production of a semiconductor laser source capable of generating an optical signal, this laser source comprising a waveguide of material III-V etched in a layer of gain material III-V, this layer of gain material III-V comprising an underlayer of crystalline material III-V doped directly extending on the layer of dielectric material, - the embodiment of the claimed modulator propagation losses and the propagation index of a guided optical signal made on the same substrate and ap to modulate the optical signal generated by the semiconductor laser source.
The embodiments of this manufacturing method may include one or more of the following features: the method comprises a step of etching the sub-layer of crystalline material III-V doped to simultaneously realize the second electrode of the modulator and a waveguide strip of III-V material in this sublayer of crystalline material III-V; the steps for producing the stack, the laser source and the modulator comprise: providing a first stack successively comprising a first support, a buried dielectric material layer and a monocrystalline silicon layer, and then localized doping. of the monocrystalline silicon layer so as to obtain a first region of the doped monocrystalline silicon layer, - a first partial localized etching of the thickness of the monocrystalline silicon layer so as to thin the thickness of the monocrystalline silicon layer. at least in the first doped region and thus obtain a first thinned doped region, while leaving the thickness of the monocrystalline silicon layer unchanged in other regions called "non-thinned", - a second total localized etching of the layer monocrystalline silicon which completely eliminates the thickness of the monocrystalline silicon layer in the regions etched during this second etching and leaves the thickness of the monocrystalline silicon layer unchanged in masked regions where this second etching is not applied, the etched and masked regions during this second etching being arranged relative to each other; to the others to structure simultaneously: - a second monocrystalline silicon waveguide in a non-thinned region of the monocrystalline silicon layer, - the first electrode of the modulator, the proximal end of the first electrode being made in the first region doped thinned, the proximal end of the first electrode then having a thickness strictly less than the thickness of the second waveguide, and then - the encapsulation of the structured monocrystalline silicon layer, in a dielectric material to obtain a layer of monocrystalline silicon encapsulated in a dielectric material, then - the collag e of a second substrate on the encapsulated monocrystalline silicon layer, then - the removal of the first support and all or part of the buried layer and the realization of the layer of dielectric material on the monocrystalline silicon layer encapsulated on the side where the first support was removed, then - the realization of the layer of gain material III-V directly on the layer of dielectric material; during the localized doping of the monocrystalline silicon layer, a second region, adjacent to the first region, is doped less strongly than the first region, and during the second etching, the etched and masked regions are arranged relative to one another to realize the distal end of the first electrode in the second doped region; the localized doping of the first monocrystalline silicon layer is carried out so as to obtain, in addition to the first doped region, an additional doped region in the monocrystalline silicon layer, the first partial localized etching is carried out so as to obtain in addition to the first thinned doped region, at least one additional thinned region in the monocrystalline silicon layer, - during the second localized total etching, the etched and masked regions are arranged to structure simultaneously, in addition to the second waveguide and of the first electrode: a third monocrystalline silicon waveguide in a non-thinned region of the monocrystalline silicon layer, and an arm extending in a transverse direction parallel to the plane of the substrate and perpendicular to the direction of propagation of the optical signal in the third waveguide, from a proximal end direc in mechanical contact with the third waveguide, to a distal end, the distal end being formed in the additional doped region of the monocrystalline silicon layer and the proximal end being formed in the additional thinned region of the monocrystalline silicon layer so that the minimum thickness of the proximal end of this arm in a direction perpendicular to the plane of the substrate is strictly less than the maximum thickness of the third waveguide in the same direction, this arm s' also extending in the direction of propagation of the optical signal in the third waveguide, then - making contactings directly in mechanical and electrical contact with the distal end of the arm to circulate a current in this distal end and warm the arm.
This embodiment of the manufacturing method further have the following advantages: - In the claimed process, the thickness of monocrystalline silicon can be adjusted as desired and, in particular, depending on the thickness of the second electrode. Thus, it is possible to place the maximum intensity of the guided optical field at the interface of the layer of dielectric material where the density variation of the charge carriers is maximum. This is not possible with the methods of manufacturing the modulators of the applications US2015 / 0055910, WO2011 / 037686 and US2009103850. Indeed, in these patent applications, the monocrystalline silicon thickness constituting the proximal end of the first electrode must be equal to the maximum thickness of the monocrystalline silicon layer. It can not be reduced only at the proximal end of the first electrode. However, in the case of a transmitter comprising a waveguide made in this silicon layer, it is the maximum thickness of this waveguide which imposes the thickness of the silicon layer. The thickness of the proximal end of the first electrode can not therefore be freely adjusted in the known methods of manufacturing a transmitter. In addition, the claimed method also makes it possible to limit the error over the width of the proximal end of the first electrode of the modulator. Indeed, in the application US2015 / 0055910, the left side of the proximal end of the silicon electrode is made during a first etching step and then the right side of this proximal end is made during a second step of engraving. If, during each etching step, the alignment error is +/- 100 nm, the error on the width W of this proximal end in the modulator of US2015 / 0055910 is then +/- 200 nm. Conversely, the claimed method allows simultaneous etching of the right and left sides of the proximal end of the first electrode. Therefore, the error in width W of the proximal end of the first electrode is only +/- 100 nm with the claimed method.
The invention will be better understood on reading the description which follows, given solely by way of non-limiting example and with reference to the drawings in which: - Figure 1 is a schematic illustration of a transmitter in vertical section; FIG. 2 is a diagrammatic illustration, in plan view, of a modulator and a phase matching device of the transmitter of FIG. 1; FIG. 3 is a flowchart of a manufacturing method of the transmitter of FIG. 1; - Figures 4 to 15 are schematic illustrations, in vertical section, of different states of manufacture obtained during the implementation of the method of Figure 3; FIGS. 16 to 19 are diagrammatic illustrations, in vertical section, of other possible embodiments of the transmitter of FIG. 1; FIG. 20 is a partial flowchart of a manufacturing method of the transmitter of FIG. 19; - Figures 21 to 24 are schematic illustrations, in vertical section, of different states of manufacture obtained during the implementation of the method of Figure 20.
In these figures, the same references are used to designate the same elements. In the remainder of this description, the features and functions well known to those skilled in the art are not described in detail.
FIG. 1 represents a transmitter 5 of an optical signal modulated in phase and / or in amplitude for transmitting information bits to a receiver via an optical fiber for example. For this purpose, the transmitter 5 comprises a laser source 7 which emits an optical signal whose phase and / or amplitude is then modulated by a system 6 of phase modulation and / or amplitude of this optical signal.
For example, the wavelength λ of the optical signal emitted by the laser source 7 is between 1250 nm and 1590 nm.
The system 6 may be a modulation system of the phase alone, or of the amplitude alone or simultaneously of the phase and the amplitude.
Typically, the laser source 7 may be a laser DBR ("distributed bragg reflector laser") or DFB ("distributed feedback laser"). Such a laser source is well known and only the details necessary for the understanding of the invention are described here. For example, for general details and operation of such a laser source, the reader may refer to the following articles: - B. Bakir B, et al., "Hybrid Si / lll-V lasers with adiabatic coupling", 2011. B. Ben Bakir, C. Sciancalepore, A. Descos, H. Duprez, D. Bordel, L. Sanchez, C. Jany, K. Hassan, P. Brianceau, V. Carron, and S. Menezo, "Heterogeneously Integrated lll-V on Silicon Lasers ", Invited Talk ECS 2014.
To simplify Figure 1 and the following figures, only a hybrid laser waveguide 200, 220 and a surface coupler 8 (known by the term "Surface grating coupler") of the laser source 7 are shown.
Such a coupler 8 is described, for example, in the following article: F. Van Laere, G. Roelkens, J. Schrauwen, D. Taillaert, P. Dumon, W. Bogaerts, D. Van Thourhout and R. Baets "Compact grating couplers between optical fibers and Silicone-on-Insulator photonic wire waveguides with 69% coupling efficiency". It is made in a layer 3 comprising monocrystalline silicon encapsulated in a dielectric material 116. Generally, a dielectric material has an electrical conductivity at 20 ° C of less than 10 "7 S / m and, preferably, less than 10" 9 S / m or 10 '15S / m. In addition, in the case of the dielectric material 116, its refractive index is strictly less than the refractive index of the silicon. For example, in this embodiment, the dielectric material 116 is silicon dioxide (SiO 2).
The layer 3 extends mainly horizontally and directly on a rigid substrate 44. In the layer 3, the monocrystalline silicon is located in the same horizontal plane parallel to the plane of the substrate 44. Here, the monocrystalline silicon of the layer 3 is also mechanically and electrically isolated from the substrate 44 by the dielectric material 116.
In Figure 1 and the following figures, the horizontal is represented by X and Y directions of an orthogonal reference. The Z direction of this orthogonal reference represents the vertical direction. Subsequently, terms such as "superior", "lower", "above", "below", "high" and "low" are defined with respect to this Z direction. are defined with respect to the X direction. The terms "forward" and "backward" are defined with respect to the Y direction.
Figure 1 shows the elements of the transmitter 5 in section in a vertical plane parallel to the X and Z directions.
For example, the maximum thickness of monocrystalline silicon in the layer 3 is between 100 nm and 800 nm. In this example, the maximum thickness of monocrystalline silicon in layer 3 is 300 nm or 500 nm.
The substrate 44 extends horizontally. In this embodiment, the substrate 44 is formed of a successive stack of a support 441 and a layer 442 of dielectric material. The thickness of the support 441 is typically greater than 200 μm or 400 μm. For example, the support 441 is a silicon support. The layer 442 is made of silicon dioxide. The thickness of the layer 442 is typically greater than 500 nm or 1 μm or more.
The hybrid laser waveguide 200, 220 consists of a waveguide 200 made of gain material III-V and a waveguide 220 in monocrystalline silicon. Generally, the waveguide 200 is used to generate and amplify an optical signal inside an optical cavity of the laser source 7. Here, for this purpose, it is produced in a layer 36 comprising a gain material. -V encapsulated in a dielectric material 117. For example, the material 117 is silicon dioxide or silicon nitride. This layer 36 extends horizontally directly on a layer 20 of dielectric material. The layer 20 itself extends horizontally directly on the layer 3, on the side of this layer 3 opposite the substrate 44.
The thickness of the layer 20 is typically between 0.5 nm and 20 nm and preferably between 1 nm and 10 nm. Here, the thickness of the layer 20 is equal to 6 nm.
The layer 36 typically comprises a doped lower sub-layer 30, a stack 34 of quantum wells or quaternary quantum boxes and an upper sub-layer 32 doped with a dopant of opposite sign to that of the sub-layer 30. The sub-layers 30 and 32 are for example here in N or P-doped InP. In this case, the stack 34 is, for example, an alternating stack of InGaAsP or Gain NAs or other sub-layers.
In Figure 1, only a strip 33, a stack 233 and a strip 234 made respectively in the sub-layer 30, the stack 34 and the sub-layer 32 are shown. This superposition of the band 33, the stack 233 and the band 234 constitutes the waveguide 200.
The waveguide 200 also comprises: - 243G and 243D contact jacks in mechanical and electrical contact directly with the band 33 and located, respectively, on the left and right of the stack 233, and - a socket 244 contact in mechanical and electrical contact directly with the strip 234.
These sockets 243G, 243D and 244 are used to inject an electric current into the waveguide 200 gain material lll-V between the sockets 243G, 243D and the socket 244.
The waveguide 220 is made of silicon and made of the monocrystalline silicon of the layer 3. This waveguide 220 extends under the band 33. In FIG. 1, the waveguide 220 is represented by way of illustration, in the particular case where the direction of propagation of the optical signal inside this waveguide is parallel to the Y direction. For example, for this purpose, the waveguide 220 adopts a configuration known as "strip". Thus, the cross section of this waveguide, parallel to the XZ plane, has a central bulge 222 from which extend on each side, parallel to the X direction, finer side arms 223G and 223D. Here, the waveguide 220 is only separated from the band 33 by a portion of the layer 20. For example, the waveguide 220 is optically connected to the waveguide 200 by adiabatic or evanescent coupling. For a detailed description of an adiabatic coupling the reader can refer to the following article: Amnon Yariv et al., "Supermode Si / lll-V hybrid Lasers, optical amplifiers and modulators: proposai and analysis" Optics Express 9147, vol . 14, No. 15, 23/07/2007.
The characteristics of the optical coupling between the waveguide 220 and the waveguide 200 depend in particular on the dimensions of the waveguide 220 and, in particular, the thickness of the central bulge 222. It is therefore important that the thickness of this bulge 222 can be adjusted independently of the dimensions of the other photonic components made on the same substrate 44. For example, here, the thickness of the bulge 222 is equal to the maximum thickness of the monocrystalline silicon in the layer 3 i.e. in this example at 300 nm or 500 nm.
To modulate the phase or the amplitude of the optical signal, the system 6 comprises at least one modulator of the propagation losses and the propagation index of a guided optical signal and, often, at least one device for phase agreement. For example, the system 6 is a Mach-Zehnder interferometer in which the modulator and the phase-tuning device are arranged in one of the branches of this interferometer to modulate the amplitude and / or the phase of the optical signal generated. by the laser source 7. The structure of a Mach-Zehnder interferometer is well known and is not described here in detail. Therefore, to simplify FIG. 1, only a modulator 100 and a phase matching device 300 are shown in vertical section parallel to the XZ plane.
The device 300 adjusts the phase of an optical signal propagating parallel to the direction Y inside a waveguide 320. For example, the waveguide 320 is longer in the direction Y is wide in the direction X. The waveguide 320 is made of silicon and made of the monocrystalline silicon of the layer 3. Here, its thickness is for example equal to the thickness of the bulge 222. The index of Silicon refraction varies greatly with temperature. Thus, by varying the temperature of the waveguide 320, it is possible to modify the speed of propagation of the optical signal in this waveguide and thus adjust the phase of the optical signal. For this purpose, the device 300 comprises two heaters 322G and 322D each disposed on a respective side of the waveguide 320. Here, the heater 322D is derived from the heater 322G by orthogonal symmetry with respect to a vertical plane parallel to the directions Y and Z passing through the middle of the waveguide 320. Thus, only the heater 322G will now be described in more detail with reference to FIGS. 1 and 2.
The heater 322G has an arm 324 extending parallel to the X direction from a proximal end 56 to a distal end 58. The arm 324 also extends parallel to the Y direction. The arm 324 is made of silicon. Here, it is made in the monocrystalline silicon of layer 3.
The proximal end 56 is directly in mechanical contact with the waveguide 320. For example, here, the proximal end 56 touches a vertical flank of the waveguide 320. For this purpose, the arm 324 and the waveguide 320 forms a single block of material.
Here, the thickness of the proximal end 56 is less than the maximum thickness of the waveguide 320 so as to confine the optical signal in the waveguide 320. For example, the thickness of the proximal end 56 is 1.5 times or twice or three times or four times smaller than the maximum thickness of waveguide 320.
The distal end 58 is doped to make the monocrystalline silicon resistive and form an electrical resistor that forms a single block of material with the waveguide 320. In FIG. 1, the doped regions of the monocrystalline silicon are finely hatched and appear dark. In this embodiment, the proximal end 56 is also doped in the same manner as the distal end 58 so that the assembly of the arm 324 is here made of doped monocrystalline silicon. The shortest distance between this doped region of the arm 324 and the waveguide 320 is, for example, strictly greater than 200 nm or 400 nm.
To circulate an electric current inside the distal end 58, the heater 322G also has two contact points 51G and 52G in mechanical and electrical contact directly with the distal end 58. Here, these 51G sockets and 52G are located one behind the other in the Y direction and at each end of the distal end 58 in this direction Y. The contact points of the heater 322D, visible in Figure 2, bear, respectively, the references 51D and 52D.
When a current, brought by the catches 51G and 52G, passes through the distal end 58, the latter transforms part of the electrical energy thus received into heat which propagates, by thermal conduction through the end 56, to the waveguide 320. Thus, the heater 322G is used to heat the waveguide 320 without any resistive element being implanted in the waveguide 320 or in the immediate vicinity of this guide. 'wave. This limits the power losses of the optical signal with respect to the case where the electrical resistance is obtained by directly doping the waveguide 320. The device 300 thus makes it possible to slowly adjust the phase of the optical signal in the waveguide. 320. On the other hand, it does not make it possible to vary the phase of the optical signal rapidly.
In contrast, the modulator 100 makes it possible to rapidly modify the phase of the optical signal. For this purpose, it comprises two electrodes 120 and 130. These electrodes 120 and 130 are also visible, in plan view, in FIG.
The electrode 120 is made of doped monocrystalline silicon. It is made in the monocrystalline silicon of the layer 3. It extends, in the X direction, from a proximal end 12 to a distal end 11. It also extends in the Y direction.
Here, the distal end 11 is more doped than the proximal end 12. For example, the concentration of dopant in the distal end 11 is between 1018 and 2 x 1019 atoms / cm3. The concentration of dopant in the proximal end 12 is for example between 1017 and 2 x 1018 atoms / cm3.
The electrode 130 is made of crystalline material III-V doped with a doping of opposite sign to that of the electrode 120. Here, it is made of InP in the underlayer 30. The dopant concentration of the The electrode 130 is, for example, between 1017 and 2 x 1018 atoms / cm3 or between 1017 and 2 x 1019 atoms / cm3.
The electrode 130 extends, parallel to the X direction, from a proximal end 32 to a distal end 31. The electrode 130 also extends in the Y direction. It is directly located on the layer 20.
The proximal end 32 is located vis-à-vis the proximal end 12 and separated from the proximal end 12 only by a portion of the layer 20 interposed between these proximal ends. With respect to a vertical plane parallel to the Y and Z directions and passing through the proximal ends 12 and 32, the distal end 31 is located on one side of this plane while the distal end 11 is located on the other side . The distal ends 11 and 31 are not vis-à-vis.
In the embodiment of Figure 1 and the following, the zone 34, which extends vertically from the distal end 31 to the substrate 44, comprises only solid dielectric materials. Here, it is about the dielectric materials 116 and the layer 20. Thanks to this, the parasitic capacitance between this end 31 and the substrate 44 is greatly reduced. More precisely, zone 34 is delimited horizontally: at the top, by a horizontal plane situated at the interface between electrode 130 and layer 20, and at the bottom, by a horizontal plane situated at the level of interface between layer 3 and substrate 44.
Zone 34 is delimited vertically by a virtual vertical edge which makes it complete turn. This vertical edge is shaped so that the orthogonal projection of the zone 34 in a horizontal plane coincides with the orthogonal projection of the distal end 31 in the same horizontal plane. The orthogonal projection of the distal end 31 in this horizontal plane corresponds to the orthogonal projection of the electrode 130 in this horizontal plane to which is subtracted the orthogonal projection of the proximal end 32 in the same plane. The orthogonal projection of the proximal end 32 in this plane is equal to the intersection of the orthogonal projections of the electrodes 130 and 120 in this horizontal plane. In the particular case where the horizontal sections of the electrodes 130 and 120 are rectangular, as shown in FIG. 2, the zone 34 is therefore delimited vertically: on the left, by a vertical plane parallel to the Y and Z directions and which passes through a vertical flank of the distal end 31 parallel to the Y and Z directions; to the right, by a vertical plane parallel to the Y and Z directions and which passes through a vertical flank of the proximal end parallel to the Y and Z directions; forward, by a vertical plane parallel to the X and Z directions and which passes through a vertical front flank of the distal end 31 parallel to the X and Z directions, and - towards the rear, by a vertical plane parallel to the directions X and Z and which passes through a vertical rear flank of the distal end 31 parallel to the X and Z directions.
In Figure 1, the area 34 has been highlighted by filling it with circles. However, here, there is no discontinuity between the dielectric materials located inside the zone 34 and those located outside this zone 34. It is for this reason that the vertical edge described above has been called "virtual".
The superposition, in the Z direction, of the proximal end 12, of a portion of the layer 20 and the proximal end 32 is sized to form a waveguide 70, capable of guiding, in the direction Y, the optical signal generated by the laser source 7. The waveguides 70 and 320 are for example optically connected to one another by an adiabatic coupler.
The maximum thickness of the proximal ends 12 and 32 is chosen so that the point M, where is the maximum intensity of the optical field of the optical signal that propagates in the waveguide 70, is as close as possible possible of the layer 20 and, preferably, located in the center of the portion of this layer 20 interposed between the proximal electrodes 12 and 32. Indeed, it is at the interfaces between the proximal ends 12, 32 and the layer 20 that the density of charge carriers is maximum when a potential difference is present between these proximal ends. Thus, by placing the point M there, the efficiency of the modulator 100 is improved. In this embodiment, the refractive indices of the proximal ends 12 and 32 are close to one another. Consequently, the maximum thicknesses of the proximal ends 12 and 32 are chosen to be substantially equal so that the point M is situated inside the layer 20. For example, the maximum thickness e 12 of the proximal end 12 is between 0 , 5e32 and 1, 5e32, and, preferably, between 0.7e32 and l, 3e32, where e32 is the maximum thickness of the proximal end 32. For example, here, the thicknesses ei2 and e32 are each chosen equal to 300 nm.
The modulator 100 also comprises two contact points 21 and 22, in mechanical and electrical contact directly with, respectively, the distal ends 11 and 30. These sockets 21 and 22 are connected to a controllable voltage source according to the bit. or bits of information to be transmitted by the transmitter 5.
One possible operation of the transmitter 5 is as follows. The laser source 7 generates an optical signal. At least a part of this optical signal is directed towards a Mach Zehnder interferometer, at least one of whose branches successively comprises the modulator 100 and the phase matching device 300. This optical signal portion is thus successively guided by the waveguide 70 and then the waveguide 320 before being recombined with another part of the optical signal guided by the other branch of the Mach Zehnder interferometer to form the modulated optical signal. For example, the waveguides 70 and 320 are optically coupled to each other by an adiabatic coupler.
A method of manufacturing the transmitter 100 will now be described with reference to Figures 3 to 15. Figures 4 to 15 show different manufacturing states of the transmitter 5 in vertical section parallel to the X and Z directions.
In a step 500, the method begins with the provision of a substrate 4. Here, this substrate 4 is a SOI substrate ("Silicon on insulator"). The substrate 4 comprises directly stacked on top of one another in the Z direction: a support 1 made of silicon, with a thickness greater than 400 μm or 700 μm conventionally, a layer 2 buried in silicon dioxide, of which The thickness is generally greater than 500 nm or 1 μm and generally less than 10 μm or 20 μm, and a monocrystalline silicon layer 43 which, at this stage, has not yet been etched or encapsulated in a dielectric material.
During a step 502, a localized doping of the layer 43 is carried out. Here, a first localized doping operation 504 is first carried out, during which doped regions 506 (FIG. These regions 506 are only performed at the locations of the future arms of the tuning device 300 and of the electrode 120 of the modulator 100. These regions 506 have a doping equal to that of the distal end 58. and the proximal end 12.
Then, a second doping operation 508 of the layer 43 is performed so as to obtain a region 510 (Figure 6) more strongly doped than the regions 506. The region 510 is here partially superimposed on one of the regions 506. For example, the region 510 is obtained by applying a new implantation on a part of one of the regions 506. The region 510 is made at the location of the future distal end 11 of the electrode 120. The doping of the region Here 510 is equal to the doping of the distal end 11.
In a step 514, the layer 43 undergoes a first partial localized etching (Figure 7) to thin the thickness of the silicon at the locations of the electrode 120 and the arms 324 322G and 322D heaters. At the end of step 514, the regions 506 and 510 are thinned and have a thickness less than the initial thickness of the layer 43. Here, the thickness of the thinned regions 506 and 510 is equal to the thickness of the the electrode 120 and arms 324.
In this step 514, the thickness of the layer 43 is also thinned in undoped regions, for example, to form the patterns of the future surface coupler 8 and the side arms 223G and 223D of the waveguide 220 Conversely, during this step 514, other so-called "non-thinned" regions are not etched and retain their initial thickness. In particular, these non-thinned regions are located at the location of the bulge 222 of the waveguide 220 and at the location of the waveguide 320.
In a step 516, a localized total etching of the layer 43 is performed (Figure 8). Unlike partial etching, total etching completely removes the thickness of silicon from layer 43 in the unmasked regions where it is applied. Conversely, masked regions protect the layer 43 of this total etching. This total etching is carried out so as to structure, simultaneously in the layer 43, the waveguides 220 and 320, the arms of the tuning device 300, the surface coupler 8 and the electrode 120. For this purpose, only the regions corresponding to these different elements are hidden. At the end of this step, the state represented in FIG. 8 is obtained.
In a step 518, the monocrystalline silicon layer 43, which has been structured in the previous steps, is encapsulated in silicon dioxide (FIG. 9). The layer 3 comprising monocrystalline silicon encapsulated in the dielectric material 116 is then obtained. The upper face of the material 116 is then prepared for bonding, for example direct or molecular bonding. For example, the upper face of the material 116 is polished using a process such as a CMP (Chemical-Mechanical Polishing) process.
In a step 520, the upper face of the substrate 4, that is to say at this stage the polished face of the material 116, is then bonded to the outer face of the substrate 44 (FIG. for example, by molecular bonding. The substrate 44 has already been described with reference to FIG.
In a step 522, the support 1 is removed, and the layer 2 is partially thinned to leave a thin layer of silicon dioxide on the layer 3. Thus, here, the layer 20 is made of removing only a portion of the layer 2 of dielectric material so as to leave a thin layer of this dielectric material which covers the layer 3 and thus forms the layer 20 (Figure 11). At the end of this step, a stack of substrate 44 and layers 3 and 20 is thus obtained.
In a step 524, a layer 36A (FIG. 12) made of gain material III-V is produced on the layer 20. For example, the layer 36A is glued on the layer 20 above the guide of FIG. wave 220 and the electrode 120. The layer 36A comprises the sub-layer 30 of doped InP with a doping of opposite sign to that of the electrode 120, the stack 34 and the underlayer 32.
In a step 526, a localized total etching (FIG. 13) of the sub-layer 32 and of the stack 34 is carried out to structure the strip 234 in the sub-layer 32 and the stack 233 in the During this step, the sub-layer 30 is not etched.
In a step 528, a localized total etching (Figure 14) of the sub-layer 30 is performed to simultaneously structure the band 33 and the electrode 130 in this sub-layer.
In a step 530, the structured layer 36A is encapsulated (FIG. 15) in the dielectric material 117. This gives the layer 36 comprising the gain material III-V encapsulated in the dielectric material 117.
Finally, during a step 532, the contacts 21, 22, 51G, 52G, 51D, 52D, 243G and 243D are made. The transmitter 5 is thus obtained as shown in FIG.
This manufacturing process has many advantages. In particular: - It allows to precisely control the thickness of the layer 20 and to obtain a particularly flat layer 20 because it is performed on the side of the layer 3 which has the same level everywhere, which simplifies the bonding of the layer 36A. It makes it possible to precisely adjust the thickness of the electrode 120 independently of the thickness of the waveguide 220 and, more generally, independently of the thickness of the monocrystalline silicon layer 43. This is particularly useful because, generally, to improve the operation of the laser source 7, it is necessary that the thickness of the waveguide 220 is large enough, that is to say here of the order of 500 nm and that the thickness of the strip 33 is quite thin, that is to say here of the order of 300 nm or 150 nm. Conversely, to improve the operation of the modulator 100, as explained above, the thickness of the electrode 120 and, in particular, its proximal end 12, must be chosen as a function of the thickness of the end proximal 32. Here, the thickness of the proximal end 32 is not possible by the thickness of the sublayer 30 crystalline InP. It is therefore 300 nm or 150 nm. - This method does not complicate the manufacture of the transmitter 5. For example, it allows to perform in one and the same etching operation, the band 33 of the waveguide 200 and the electrode 130 of the modulator 100. Similarly, The electrode 120 and the waveguide 220 are produced simultaneously during the same etching operation. This method makes it possible to avoid the formation of a parasitic capacitance under the distal end 31 and therefore a faster operation of the modulator 100.
Figure 16 shows a transmitter 550 identical to the transmitter 5 except that the substrate 44 is replaced by a substrate 552. The substrate 552 is identical to the substrate 44 except that the layer 442 is omitted. The manufacturing method of the transmitter 550 is, for example, the same as that described for the transmitter 5 except that in step 520, the substrate 552 is used instead of the substrate 44.
FIG. 17 represents a transmitter 560 identical to the transmitter 5 except that the modulator 100 is replaced by a modulator 562. The modulator 562 is identical to the modulator 100 except that the electrode 120 is replaced by an electrode 564. The electrode 564 is identical to the electrode 120 except that the distal end 11 is replaced by a distal end 566. The distal end 566 is identical to the distal end 11 except that its maximum thickness here is greater than the thickness of the distal end. At the proximal end 12, the thickness of the distal end 566 is equal to the maximum thickness of the waveguide 220 and thus of the monocrystalline silicon layer 43.
FIG. 18 represents a transmitter 570 identical to the transmitter 550 except that the modulator 100 is replaced by a modulator 572. The modulator 572 is identical to the modulator 100 except that the electrode 120 is replaced by an electrode 574.
The electrode 574 is identical to the electrode 120 except that the proximal end 12 and the distal end 11 are mechanically and electrically tuned to each other by an intermediate portion 576 whose thickness e5 6 is strictly less than the maximum thickness of the proximal end 12. The intermediate portion 576 is separated from the layer 20 by a recess 578 filled with a dielectric material. Here the recess 578 is filled with the material 116. The bottom of this recess is essentially horizontal and spaced from the layer 20 by a depth p578. The depth p5-8 is typically greater than 50 nm or 100 nm. Here, the depth p57s is equal to 150 nm. This conformation of the electrode 574 allows a better control of the width of the waveguide 70. Indeed, in this embodiment, the width of the waveguide 70 is only fixed by the width W of the proximal end. 12 in the direction X. Indeed, the portions of the electrode 130 which protrude, in the X direction, from the proximal end 12 are isolated from the electrode 574 by the recess 578. This width W is, by etching, defined to +/- δ near, where δ is an error equal to, typically, +/- 5 nm, or +/- 10 nm. This conformation of the electrode 574 therefore makes it possible to be less sensitive to the positioning errors of the electrode 130. Indeed, this positioning is done by lithographic alignment, with a λal precision typically equal to +/- 30 nm, or +/- -100nm. In the absence of the recess 578, the width W of the waveguide 70 is defined by the width of the overlap of the electrodes 130 and 120 and therefore with an error of +/- δal. Moreover, the embodiment of FIG. 18 allows a better control of the capacity of the modulator. For example, it has been calculated that the error on the capacity of the modulator 572 is of the order of 1.6% whereas in the absence of the recess 578, this error would be close to 25%.
The thickness e576 is chosen so as to prevent or limit the propagation of the optical signal in the distal end 11. Here, this thickness e576 is also less than the thickness of the proximal end 12. For example, the thickness e576 is less than or equal to 0.5 x e12, where e12 is the maximum thickness of the proximal end 12. Here, the thickness e576 is equal to 150 nm and the thickness e12 is equal to 300 nm . For example, the portion 576 is made using an additional localized partial etching operation implemented between the steps 514 and 516 of the method of FIG.
FIG. 19 represents a transmitter 600 identical to the transmitter 5 except that: the waveguide 220 is replaced by a waveguide of 610; the surface coupler 8 is replaced by a surface coupler 608; arm of the tuning device are replaced by arms 612G and 612D, and - the electrode 120 is replaced by an electrode 614.
The electrode 614 comprises: a proximal end 618 vis-à-vis the proximal end 32 of the electrode 130, a distal end 616 mechanically and electrically directly connected to the socket 21, and a intermediate portion 620 which mechanically and electrically connects the ends 616 and 618.
In contrast to the previous embodiment, the thickness of the proximal end 618 is here equal to the maximum thickness of the waveguide 610. This thickness is here equal to the maximum thickness of the layer 43 in FIG. monocrystalline silicon. This embodiment always has the advantage of having, under the distal end 31 of the electrode 130, the zone 34 consisting solely of solid dielectric material. Thus, the modulator of the transmitter 600 has only negligible parasitic capacitance at this location and its operation is therefore faster than the modulator described in the application US2015 / 0055910.
In this embodiment, the thickness of the distal end 616 is equal to the thickness of the proximal end 618. The thickness of the intermediate portion 620 is strictly lower and, preferably twice lower, at the thickness of the proximal end 618 to prevent the propagation of the optical signal in the distal end 616. As in the embodiment of Figure 18, the intermediate portion 620 is separated from the layer 20 by a recess 622 fills material 116. Intermediate portion 620 and recess 622 are formed as described for intermediate portion 576 and recess 578 so as to retain the advantages of the embodiment of Figure 18.
A method of manufacturing the transmitter 600 will now be described with reference to Figures 20 to 24.
The method starts with identical steps 650 and 652, respectively, at steps 500 and 502. The state shown in FIG. 21 is then identical, which is identical to the state represented in FIG. 6 except that the doped regions 506 and 510 are not exactly in the same locations.
In a step 654, the layer 43 undergoes a localized partial etching (FIG. 22) such as that described with reference to step 514 for thinning the monocrystalline silicon at the location of the future intermediate portion 620. Localized partial etching is also used to thin, at the same time, the monocrystalline silicon at the locations of the future arms 612G and 612D, the side arms of the waveguide 610 and the surface coupler 608.
In a step 656, the layer 43 undergoes a localized total etching (FIG. 23) to structure simultaneously in the monocrystalline silicon, the electrode 614, the surface coupler 608, the arms 612G and 612D and the guide of FIG. wave 610. This step is performed, for example, as described for step 516.
In a step 658 (Figure 24), the monocrystalline silicon is encapsulated in silicon dioxide. The layer 3 of monocrystalline silicon encapsulated in the dielectric material 116 is thus obtained. The upper face of the material 116 is then prepared for direct bonding. This step is similar to step 518 previously described.
Then, the manufacture of the transmitter 600 continues with the steps 524 to 532 of the method of Figure 3. To simplify Figure 20, these steps have not been shown.
Many other embodiments are possible. For example, the modulator 100 may also be a ring modulator. For this purpose, the waveguide 70 closes on itself to form an annular waveguide in which the density of the charge carriers can be varied according to the potential difference applied between the sockets 21 and 22. Typically, this annular waveguide is connected to a waveguide in which the optical signal to be modulated propagates by an evanescent coupling. In this case, the phase tuning device 300 may be omitted. The waveguide 70 may also constitute only a limited portion of the annular waveguide.
In another embodiment, the modulator is used to modulate the intensity of the optical signal passing therethrough. Indeed, a change in the density of the charge carriers in the waveguide 70 also changes the intensity of the optical signal passing through it.
Alternatively, only the proximal end 12 is thinned and the distal end 11 is not. Thus, in this embodiment, for example, the thickness of the end 11 is equal to the thickness of the monocrystalline silicon layer 43. Indeed, to center the point M, where is the maximum intensity of the optical field of the optical signal at the center of the layer 20, it is the thickness of the ends 12 and 32 which is important. The thickness of the distal ends 11 and 31 is not significant in this respect.
In a variant, the doping of the proximal end 12 and the distal end 11 are the same. Therefore, during the manufacture of the electrode 120, one of the two doping steps of the monocrystalline silicon layer 43 may be omitted.
Other dielectric materials are possible for the material 116 and the layer 20. For example, it may be silicon nitride, aluminum nitride, an electrically insulating polymer, Al 2 O 3. In addition, in the case of layer 20, its refractive index is not necessarily less than that of silicon.
In another variant, the layer 20 is completely eliminated where it is not essential for the operation of the transmitter. For example, it is completely eliminated except between the proximal ends 12 and 32 and between the waveguide 220 and the band 33. In another variant, the layer 20 is also eliminated between the waveguide 220 and the band 33. .
Other gain materials III-V are possible to produce the layer 36. For example, the layer 36 is formed of the following stack from bottom to top: - a lower sublayer doped GaAs N, - Al GaAs quantum can sub-layers, or AIGaAs quantum wells, and - an upper P-doped GaAs sublayer.
[00103] The III-V material used to make the underlayer 30 may be different. For example, it may be AsGa doped N or P. It will also be noted that the P-doped InP has more optical loss than the N-doped InP, and that it is therefore preferable to use at the modulator level. for the electrode 130 of the N-doped InP
In another embodiment, the electrode 130 is made of a material III-V different from that used to make the strip 33. In this case, the electrode 130 and the strip 33 are not structured in a same undercoat material III-V.
Whatever the embodiment, it is possible to invert the N and P doped regions.
Alternatively, some or all of the contacts are made, not through the material 117, but through the substrate 4, 44 or 552. In this case, compared to what has been shown on In the preceding figures, one or more electrical contact points emerge under the substrate.
Alternatively, the waveguides 70, 220, 320, 610 are curved. In this case, the conformation of the different elements optically coupled to these waveguides is adapted to the radius of curvature of these waveguides.
The waveguide 220 can take a configuration called "strip" that is to say that the side arms 223G and 223D are omitted or any other configuration capable of guiding an optical signal.
Alternatively, the heater 322D is omitted. In another variant, the thickness of the distal end 58 is strictly greater than the thickness of the proximal end 56. For example, the thickness of the distal end 58 is equal to the maximum thickness of the guide wire. wave 320.
The doping of the proximal end 56 may be different from that of the distal end 58. For example, the doping of the proximal end 56 may be equal to that of the distal end 11 or different. In another variant, the proximal end 56 is not doped.
[00111] Other manufacturing methods are possible. For example, the insulating layer 20 can be obtained by different manufacturing processes. For example, the step 522 is replaced by a step in which the layer 2 is completely removed to the layer 3 and the layer 20 is deposited on the layer 3 laid bare. In this case, optionally, the layer 20 may be made of a dielectric material different from the material 116 such as an electrically insulating polymer or Al 2 O 3. After the complete removal of the layer 2, it is also possible to make the layer 20 by oxidation of the surface of the layer 3 or by oxidation of the underlayer 30 of III-V material before bonding it directly to the layer 3.
In another variant, the second localized total etching is replaced by a uniform etching of the entire surface of the layer 3 to transform the unthinned regions into thinned regions and completely eliminate the thinned regions.
The various embodiments of the phase matching device described above can be implemented independently of the different embodiments of the modulator. In particular, the phase-tuning device can be used in any photonic system where it is necessary to tune the phase of an optical signal propagating in a silicon waveguide and it does not matter that this system has a modulator as claimed herein. For example, the tuning device can also be implemented in a photonic system using a modulator such as that described in the application US2015 / 0055910. It can also be used in a photonic system having no modulator.

权利要求:
Claims (13)
[1" id="c-fr-0001]
A modulator (100; 562; 572) of propagation losses and the propagation index of a guided optical signal, said modulator comprising: - a substrate (1,2,44,552) extending mainly in a a plane referred to as a "plane of the substrate" and a layer (3), comprising monocrystalline silicon, extending directly on this substrate and mainly parallel to the plane of the substrate, - a first electrode (120; 564; 574; 614) of monocrystalline silicon P or N-doped dopant in the monocrystalline silicon of the layer (3) having monocrystalline silicon, said first electrode extending in a transverse direction (X) parallel to the plane of the substrate, from a proximal end (12; at a distal end (11; 566; 616), and extending longitudinally in the direction (Y) of propagation of the optical signal; - a second electrode (130) of doped crystalline material III-V having a doping of opposite sign to the one of the first electrode, said second electrode extending in the transverse direction (X) from a proximal end (32) facing the proximal end (12; 618) of the first electrode (120; 564; 574; 614) to a distal end (31) on a side opposite the distal end (11; 566; 616) of the first electrode (120; 564); 574; 614) with respect to an axis perpendicular to the plane of the substrate and passing through the proximal ends (12; 618; 32), which second electrode (130) extends longitudinally also in the direction (Y) of propagation of the optical signal a dielectric material layer (20) interposed between the proximal ends (12; 618, 32) of the first and second electrodes to electrically isolate them from each other; - a first waveguide (70) capable of guiding the optical signal to be modulated in the direction (Y) of propagation of the optical signal, this first waveguide being formed by the proximal ends (12; 618, 32) of the electrodes and the portion of the layer (20). dielectric material interposed between these proximal ends (12; 618, 32), - contacts (21, 22) directly in mechanical and electrical contact with, respectively, the distal ends (11; 566; 616, 31) electrodes (120; 564; 574; 614,130) for electrically connecting the first and second electrodes to different electrical potentials so as to change the charge carrier density within the first waveguide (70) - an area (34) extending in the direction perpendicular to the plane of the substrate from the distal end (31) of the second electrode to the substrate (1, 2; 44; 552). , and - in the transverse direction (X) and in the direction (Y) of propagation of the optical signal, under the whole of the distal end (31) of the second electrode (130), characterized in that this zone (34) ) is solely composed of one or more solid dielectric materials (20, 116).
[2" id="c-fr-0002]
The modulator according to claim 1, wherein the maximum thickness of the proximal end (12) of the first electrode (120; 564; 574) is strictly less than the maximum thickness of the monocrystalline silicon of the layer (3). comprising monocrystalline silicon.
[3" id="c-fr-0003]
The modulator according to claim 2, wherein the maximum thickness of the proximal end (12) of the first electrode (120; 564; 574) is between 0.7e32 and 1, 3e32, where e32 is the thickness maximum of the proximal end (32) of the second electrode (130).
[4" id="c-fr-0004]
4. Modulator according to any one of the preceding claims, wherein the second electrode is made of InP or AsGa.
[5" id="c-fr-0005]
5. Photonic transmitter comprising: - a successive stack of a substrate (1, 2; 44; 552) extending mainly in a plane called "plane of the substrate", a layer (3) comprising monocrystalline silicon encapsulated in a dielectric material and extending directly on this substrate, and a layer (20) of dielectric material extending directly on the layer (3) comprising monocrystalline silicon, these layers extending mainly parallel to the plane of the substrate, a semiconductor laser source (7) capable of generating an optical signal, this laser source comprising a first waveguide (200) of material III-V etched in a layer of gain material III-V, this layer of gain material III-V having an underlayer (30) of doped crystalline material III-V extending directly on the layer (20) of dielectric material, - a modulator (100; 562; 572) of propagation losses. and the propagate index ion of a guided optical signal produced on the same substrate (1, 2; 44; 552) and adapted to modulate the optical signal generated by the semiconductor laser source, characterized in that the modulator is according to any one of the preceding claims.
[6" id="c-fr-0006]
6. The transmitter of claim 5, wherein the second electrode (130) of this modulator is etched in the sub-layer (30) of doped crystalline material III-V extending directly on the layer (20) of dielectric material.
[7" id="c-fr-0007]
7. Transmitter according to any one of claims 5 to 6, wherein: the semiconductor laser source comprises a second waveguide (220; 610) made in the monocrystalline silicon of the layer (3) comprising monocrystalline silicon and located under the first waveguide (200) of III-V material, this second waveguide being optically connected to the first waveguide (200) of III-V material by evanescent or adiabatic coupling, and - the maximum thickness of the proximal end (12) of the first electrode (120; 564; 574) is different from the maximum thickness of the second waveguide (220; 610).
[8" id="c-fr-0008]
8. Transmitter according to any one of claims 5 to 7, wherein the transmitter also comprises: - a third waveguide (320) adapted to guide the optical signal generated by the laser source and made in the monocrystalline silicon of the layer (3) comprising monocrystalline silicon, - a tuning device (300) for the phase of the optical signal propagating in this third waveguide (320), this tuning device (300) comprising: arm (324; 612G, 612D) made in the monocrystalline silicon of the layer (3) having monocrystalline silicon and which extends in a transverse direction (X) parallel to the plane of the substrate and perpendicular to the direction (Y) of propagating the optical signal in the third waveguide (320) from a proximal end (56) directly in mechanical contact with the third waveguide (320) to an N or P doped distal end (58) , the minimum thickness of the end proximal to this arm in a direction perpendicular to the plane of the substrate being strictly less than the maximum thickness of the third waveguide in the same direction, this arm also extending in the direction of propagation of the optical signal in the third waveguide. wave (320) • contacts (51G, 52G, 51D, 52D) directly in mechanical and electrical contact with the distal end (58) to circulate a current in this distal end adapted to heat the waveguide by thermal conduction through the arm (324; 612G, 612D).
[9" id="c-fr-0009]
9. A method of manufacturing a photonic semiconductor transmitter, said method comprising: - the embodiment (522) of a stack of a substrate (1, 2; 44; 552) successively extending in a plane called "plane of the substrate", of a layer (3) comprising monocrystalline silicon and extending directly on this substrate, and of a layer (20) of dielectric material extending directly on the layer (3) comprising monocrystalline silicon, these layers extending mainly parallel to the plane of the substrate, - the production of a semiconductor laser source capable of generating an optical signal, this laser source comprising a waveguide (200) of material V engraved in a layer of gain material III-V, this layer of gain material III-V comprising an underlayer (30) of crystalline material III-V doped extending directly on the layer (20) of material dielectric, - the production of a modulator (1 00; 562; 572) propagation losses and the propagation index of a guided optical signal formed on the same substrate (1, 2; 44; 552) and adapted to modulate the optical signal generated by the semiconductor laser source, characterized in that the modulator produced is in accordance with any one of claims 1 to 4.
[10" id="c-fr-0010]
10. The method of claim 9, wherein the method comprises a step of etching the sub-layer (30) of crystalline material III-V doped to simultaneously realize the second electrode (130) of the modulator and a strip (33) of the waveguide (200) made of III-V material in this sublayer (30) of crystalline material III-V
[11" id="c-fr-0011]
11. Method according to any one of claims 9 to 10, wherein the steps of producing the stack, the laser source and the modulator include: - the supply (500) of a first stack comprising successively a first support (1), a layer (2) buried in dielectric material and a layer (43) monocrystalline silicon, and - localized doping (502) of the layer (43) monocrystalline silicon so as to obtain a first region of the layer in doped monocrystalline silicon, - a first partial localized etching (514) of the thickness of the monocrystalline silicon layer (43) so as to thin the thickness of the monocrystalline silicon layer (43) at least in the first doped region and thus obtain a first thinned doped region, while leaving the thickness of the monocrystalline silicon layer (43) unchanged in other regions called "non-thinned", - a second local total etching isée (516) of the layer (43) of monocrystalline silicon which completely eliminates the thickness of the layer (43) of monocrystalline silicon in the etched regions during this second etching and leaves the thickness of the layer (43) silicon unchanged monocrystalline in masked regions where this second etching is not applied, the regions etched and masked during this second etching being arranged with respect to one another to structure simultaneously: a second silicon waveguide (220) monocrystalline in a non-thinned region of the monocrystalline silicon layer (43), the first electrode (120; 564; 574) of the modulator, the proximal end (12) of the first electrode (120; 564; 574) being formed in the first thinned doped region, the proximal end (12) of the first electrode (120; 564; 574). then having a thickness strictly less than the thickness of the second waveguide, and then - encapsulating (518) the layer (43) structured monocrystalline silicon, in a dielectric material (116) to obtain a layer (3) of monocrystalline silicon encapsulated in a dielectric material, then - bonding (520) of a second substrate (44; 552) on the encapsulated monocrystalline silicon layer (3), then - removing (522) of the first support (1) and all or part of the buried layer (2) and making the layer (20) of dielectric material on the monocrystalline silicon layer (3) encapsulated on the side where the first support (1) has been removed, and then - the producing (524) the layer (36) of gain material lll-V directly on the layer (20) of dielectric material.
[12" id="c-fr-0012]
The method according to claim 11, wherein: during the localized doping (502) of the monocrystalline silicon layer (43), a second region, adjacent to the first region, is doped less strongly than the first region, and in the second etching (516), the etched and masked regions are arranged relative to one another to provide the distal end (11; 566) of the first electrode (120; 564; 574) in the second doped region.
[13" id="c-fr-0013]
13. A method according to any one of claims 11 to 12, in which: the localized doping (502) of the first monocrystalline silicon layer (43) is produced so as to obtain, in addition to the first doped region, a additional doped region in the monocrystalline silicon layer (43), - the first partial localized etching (514) is carried out so as to obtain, in addition to the first thinned doped region, at least one additional thinned region in the layer (43) in monocrystalline silicon, in the second localized total etching (516), the etched and masked regions are arranged to structure simultaneously, in addition to the second waveguide (220) and the first electrode (120; 564; 574; 614): - a third waveguide (320) of monocrystalline silicon in a non-thinned region of the monocrystalline silicon layer (43), and - an arm (324) extending in a parallel transverse direction at the plane of the substrate and perpendicular to the direction of propagation of the optical signal in the third waveguide (320), from a proximal end (56) directly in mechanical contact with the third waveguide (320), to a distal end (58), the distal end (58) being formed in the additional doped region of the monocrystalline silicon layer (43) and the proximal end (56) being formed in the additional thinned region of the layer (43); ) of the monocrystalline silicon so that the minimum thickness of the proximal end (56) of this arm in a direction perpendicular to the plane of the substrate is strictly less than the maximum thickness of the third waveguide (320) in the same direction, this arm also extending in the direction of propagation of the optical signal in the third waveguide (320), then - the realization (532) of contact points (51G, 52G, 51D, 52D) directly in contact mechanical and electrical with the distal end (58) of the arm (324) to circulate a current in this distal end and thereby heat the arm.

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2017-02-28| PLFP| Fee payment|Year of fee payment: 2 |

2017-08-18| PLSC| Publication of the preliminary search report|Effective date: 20170818 |

2018-02-26| PLFP| Fee payment|Year of fee payment: 3 |

2020-02-28| PLFP| Fee payment|Year of fee payment: 5 |

2021-02-26| PLFP| Fee payment|Year of fee payment: 6 |

优先权:

申请号 | 申请日 | 专利标题

FR1651138A|FR3047811B1|2016-02-12|2016-02-12|MODULATOR OF PROPAGATION LOSSES AND OF THE PROPAGATION INDEX OF A GUIDE OPTICAL SIGNAL|

FR1651138|2016-02-12|FR1651138A| FR3047811B1|2016-02-12|2016-02-12|MODULATOR OF PROPAGATION LOSSES AND OF THE PROPAGATION INDEX OF A GUIDE OPTICAL SIGNAL|

EP17153847.3A| EP3206079B1|2016-02-12|2017-01-30|Photonic transmitter|

US15/425,291| US9871343B2|2016-02-12|2017-02-06|Photonic transmitter with waveguide formed of particular opposing electrodes|

JP2017020069A| JP2017143262A|2016-02-12|2017-02-07|Photonic transmitter|

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