• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
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    • 专利摘要:
    Method and reconfigurable device for the guidance of an optical signal with two perpendicular polarizations. The present invention relates to a method and a reconfigurable device for guiding an optical signal with two perpendicular polarizations comprising: an input means for guiding the optical signal; means of exit; a birefringent element, disposed between the input means and the output means, which determines a first optical path for each of the two perpendicular polarizations, wherein said birefringent element is switchable between two alignment states; an electromagnetic field source applicable to the birefringent element, capable of switching the state of alignment of the birefringent element and determining a second optical path for each of the two perpendicular polarizations of the optical signal in the output means. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2671218A1
    申请号:ES201830088
    申请日:2018-02-01
    公开日:2018-06-05
    发明作者:Manuel CAÑO GARCIA；Jose Manuel Oton Sanchez；Morten Andreas Geday；Patxi Xabier QUINTANA ARREGUI；Ahmed ELMOGI；Marie-aline MATTELIN；Jeroen Missinne；Geert Van STEENBERGE
    申请人:Universiteit Gent；Universidad Politecnica de Madrid；
    IPC主号:
    专利说明:

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    Figures 4A-4B.- show a detailed view of the alignment states of the parallel flat sheet as a function of the variation in the frequency of the applied electric field.
    Figures 5A-5B.- show a cut in the plane containing the waveguides with a particular configuration and selection of materials, according to one of the embodiments of the invention.
    Figures 6A-6B.- show a cut in the plane containing the waveguides with a particular configuration and selection of materials, according to one of the embodiments of the invention.
    Figures 7A-7B.- show a cut in the plane containing the waveguides with a particular configuration and selection of materials, according to one of the embodiments of the invention. DETAILED DESCRIPTION OF THE INVENTION
     The present invention relates to a guidance device for the separation / recombination of perpendicular linear light polarizations (TE / TM) in dielectric waveguides. It is based on the current integrated photonic circuit (PIC) platforms and the addition of LC liquid crystal.
     The polarization TE refers to that which is parallel to the substrate and the polarization TM to which is perpendicular to the substrate; This convention is the one used in integrated optics. For the effective index of the mode that propagates with polarization TE nTE is used, similarly, for the effective index of the mode that propagates with polarization TM, nTM is used. The LC has two refractive indices, depending on its spatial orientation, an ordinary refractive index (no) and an extraordinary refractive index (ne). Likewise, it is also advisable to define the principal vector, as a vector of an orientation nature, which indicates the orientation of the molecules along their long axis (normally coincides with the direction of ne).
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     The device of the present invention, according to one of its embodiments illustrated in the cross-section along the waveguide of Figure 1, comprises a sandwich-shaped structure where two substrates face and join. The first substrate 1 has a first electrode 2.a that supports the materials
    image15 used to make the waveguides (in this document it is understood as a waveguide any set of materials (core and cover) that guide the light at the desired wavelength) with cover 3 and core 4, where there is at least one entry guideline 4.ay at least one output 4.b. At the intersection between the entrances and the exits a cavity 5 is arranged in the form of a flat parallel sheet inserted at an angle
     image16  Regarding the waveguide. The surface of the cavity is treated with an alignment layer 6. and subsequently filled with an LC 7. All this is covered with the second substrate 8, where a second electrode 2.b treated with an alignment layer has previously been deposited. 6.b, attached to the first substrate forming a sandwich, as is conventionally done with the LC screens.
    The guiding device of the present invention is dependent on the wavelength of the light used and can operate at wavelengths of the incident light ranging from the visible to the near infrared. The present invention makes use of the optical and dielectric anisotropy of the LC by intersecting a sheet
    image17
    image18 flat parallel with a certain angle on the guide. The different indexes of refraction experienced by the optical signal that propagates according to the different polarizations, produces different optical paths for each polarization, causing them to be guided in different waveguides at the exit of the parallel plane sheet.
     The guiding device can adopt various configurations, depending on the materials used and the desired functionality (such as a switch
    or a polarization separator). Depending on the ratio of refractive indexes of the waveguides and the birefringent material (LC), the device shows three different behaviors: as polarizer / polarization insulator, selecting a
    image19 of the two linear polarizations of the incident optical signal, as an optical switch, obstructing or allowing the passage of light through the output waveguides, and as a switch
    image20


    of polarizations, causing the linear polarizations of the optical signals of the inputs to be exchanged in the output waveguides.
    A general view perpendicular to the substrate is shown in Figure 2. This
    image21 formed by a main image 2A and five secondary images 2B, 2C, 2D, 2E, 2F. In the main image 2A you can see an input waveguide 20, two output waveguides 21 and the parallel flat sheet 22 that intersects the waveguides. In the secondary figures, several embodiments with different geometries are shown, depending on the refractive indexes of the materials used. The differences between geometries are given by Snell's Law and the combination of refractive indices of birefringent material (no, ne) with the index with which guided modes are propagated in the waveguide (nTE, nTM). Snell's law is determined by the equation:
    image22
    where
    image23 1 and
    image24 2 are the angles of entry and exit with respect to the normal of the plane-parallel sheet, n1 for our case would be the propagation indices of the modes (nTE, nTM) and n2 would be the refractive indices of (no, ne) that they change according to the polarization of the guided mode and the orientation of the birefringent material.
     Thus, the geometries only differ in the position of the exit waveguides. These waveguides have been positioned by carefully calculating the signal deviation
    image25 optics due to the change in refractive index at the plane-parallel intersection. This causes a change in the angle that, together with the width of the cavity, determines its positioning. In the secondary images 2B-2F it is schematized where the waveguides are arranged depending on the relationship between refractive indices for a cavity of constant width and a certain angle.
    image26
     Assuming a positive dielectric anisotropy LC (the master vector aligns with the direction of the electric field), the effective index of the LC inside the cavity for the light that propagates according to the TE mode, in the plane containing the waveguides, comes determined by the equation:
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     Figures 5A and 5B represent an LC with properties such that no <nTE, TM and ne >> nTE, TM. When voltage is applied to a positive electrical anisotropy LC or in the case of a dual frequency LC, voltage is applied to the frequency corresponding to the parallel configuration (voltage of the necessary frequency for the LC of
    image30 dual frequency is aligned parallel to the field), the one illustrated in Figure 5A is obtained where the optical signal that propagates according to the TE mode is diverted outside the waveguides and dispersed in the cover, while the optical signal that propagates according to the TM mode is guided to waveguide 52. If the LC has negative electrical anisotropy, the opposite effect would be had, but the device remains equally valid. In the figure
    image31 5B, where the waveguide 50 is an extension of the input 51, a zero voltage is applied or, in the case of a dual frequency LC, voltage is applied to the perpendicular configuration frequency (voltage to the frequency necessary for the frequency LC dual align perpendicular to the field). In this case the optical signal that propagates with TM polarization is diverted out of the waveguides and dispersed on the cover, while
    image32 that the one that propagates with polarization TE is guided to output 52.
     Figures 6A and 6B represent an embodiment with properties such that no
    image33 nTE, TM and ne >> nTE, TM. This design consists of two parallel waveguides and its main difficulty lies in the selection of materials, since it must not coincide with nTE, TM.
     image34 For voltage applied with a positive electrical anisotropy LC or, in the case of a dual frequency LC, voltage applied to a parallel configuration frequency, the situation shown in Figure 6A is obtained, where the optical signal that propagates according to the mode TE continues on the waveguide 60 and the optical signal that propagates according to the TM mode continues on the waveguide 62. On the other hand, when there is no voltage or, if there is a
     image35 Dual frequency LC applies a voltage with perpendicular configuration frequency, the situation in Figure 6B is given, where the optical signal that propagates according to the TE mode is diverted to the output 62, and the optical signal that propagates according to the TM mode continues straight on 60.
    image36 Figures 7A and 7B represent an embodiment with properties such that no <nTE, TM and ne >> nTE, TM. The main difference with the set of figures 5 and 6 is the positioning of outputs 70 and 72, which is a more complex design in which
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    In addition, it must be provided with the appropriate electrical connections to be able to apply the electrical fields necessary to switch the LC on the plane-parallel sheet.
    The device can be cascaded, that is, on the same chip, several interconnected devices can be used using the different functionalities described, thus obtaining a more complex device, capable of manipulating the polarizations of the optical signal.
     According to a preferred embodiment of the present invention, the manufacture of a reconfigurable guidance device comprises the following steps:
     - First, two flat substrates are selected. The material from which the substrates are made can be glass, quartz, transparent polymers such as PMMA, ceramics, silicon or other inert and rigid materials. Both substrates must be suitable (and conditioned) for the deposition of layers described below.
     - A conductive layer is created on both substrates by any deposition process.
     -  On one of the conductive layer substrates, the lower cover layer is grown / deposited. Depending on the platform used, it can be made of inorganic material such as SiO2 or organic (low refractive index polymers).
    -On the lower cover the core layer of the waveguide is grown / deposited, Made of a transparent material (without losses) at the desired wavelength and whose main characteristic is that its index of refraction must be greater than that of the cover . In this layer the waveguide is engraved by any lithographic procedure: photolithography and attack, photolithography by stamping (NIL), laser direct writing processes (DWL) or others.
     - Once the recording of the core is finished, a cover layer is deposited, the top cover. Up to this point the process is equivalent to the normal manufacturing process of a PIC.
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    权利要求:
    Claims (1)
    [1]
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    同族专利:
    公开号 | 公开日
    ES2671218B2|2018-12-04|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2001033289A1|1999-11-01|2001-05-10|Corning Incorporated|LIQUID CRYSTAL PLANAR NON-BLOCKING NxN CROSS-CONNECT|
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