CN116165820A

CN116165820A - LCOS device and WSS

Info

Publication number: CN116165820A
Application number: CN202111417471.9A
Authority: CN
Inventors: 闻远辉; 李健雄; 宗良佳
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-11-25
Filing date: 2021-11-25
Publication date: 2023-05-26
Also published as: WO2023093063A1

Abstract

The application provides a liquid crystal on silicon LCOS device and a wavelength selective switch WSS. In this application, the LCOS device includes an over-structured surface, where the over-structured surface may convert a polarization direction of an optical signal having a received polarization direction that is a first direction into a second direction, and convert a polarization direction of an optical signal having a received polarization direction that is a second direction into the first direction. The liquid crystal box can adjust the phase of the optical signal with the polarization direction being the first direction in the optical signals output by the first transparent electrode and the super-structure surface according to the target voltage. It follows that LCOS devices can perform polarization diversity processing and conversion processing on optical signals through the super-structured surface. The super-structured surface is simple in implementation mode, occupies small volume, reduces the complexity of equipment, reduces the construction cost of the equipment, and is more beneficial to realizing technical popularization.

Description

LCOS device and WSS

Technical Field

The present application relates to the field of communications, and in particular to a liquid crystal on silicon (Liquid Crystal on Silicon, LCOS) device and wavelength selective switch (Wavelength Selective Switch, WSS).

Background

LCOS is a miniaturized reflective active matrix liquid crystal display device or "microdisplay device". LCOS devices are also known as spatial light modulators. The top of the silicon substrate in LCOS devices is covered with a liquid crystal layer that modulates the light field. LCOS devices have the advantages of flexible light field control, repeatable erasing, high resolution, and the like, and therefore, LCOS devices are widely used in various fields.

In the conventional art, the material of the liquid crystal layer in LCOS devices is mainly nematic liquid crystal. Nematic liquid crystals are mainly composed of nonpolar rod-like liquid crystal molecules and have uniaxial crystal characteristics. In implementing optical field phase modulation, a conventional LCOS device is assumed to define a plane in which the LCOS device is located as an XY plane, and a normal direction of the XY plane is defined as a Z direction. In the XY plane, the orientation of the long axes of liquid crystal molecules under no voltage is defined as the X direction, and the direction orthogonal to both the X and Z directions is defined as the Y direction. When a voltage is applied to a conventional LCOS device, the orientation of the liquid crystal molecules can be rotated from the X-direction to the Z-direction. When the voltage is different, the orientation of the liquid crystal molecules is different in the angle of rotation from the X direction to the Z direction. Thus, the liquid crystal molecules at different voltages are oriented in different directions within the XZ plane. At this time, the incident light polarized in the X direction corresponds to extraordinary light (extraordinary light), abbreviated as e light, and the refractive index thereof changes with the orientation of the liquid crystal molecules. Therefore, the incident light polarized in the X direction can be phase modulated by adjusting the voltage applied to the LCOS device while the thickness of the liquid crystal layer remains unchanged. The incident light polarized in the Y direction corresponds to an ordinary light (o light), and the refractive index of the light does not change with the orientation of the liquid crystal molecules, so that the phase modulation cannot be realized.

In conventional LCOS devices, when incident light has polarized components in both directions of X, Y, it is generally necessary to perform polarization diversity processing and conversion processing on the optical signal by means of a peripheral optical path including a plurality of elements. In the equipment comprising the traditional LCOS device, a peripheral light path is required to be arranged in a matched mode, the peripheral light path is complex in structure and large in occupied volume, the complexity of the equipment is improved, and the construction cost of the equipment is increased.

Disclosure of Invention

The application provides a liquid crystal on silicon LCOS device and a wavelength selective switch WSS, wherein the WSS comprises the LCOS device, and the LCOS device can perform polarization diversity processing and conversion processing on optical signals through an ultra-structured surface. The super-structured surface is simple in implementation mode, occupies small volume, reduces the complexity of equipment, reduces the construction cost of the equipment, and is more beneficial to realizing technical popularization.

A first aspect of the present application provides a liquid crystal on silicon LCOS device, comprising a first transparent electrode, a liquid crystal cell, an superstructural surface, an electrode layer and a driving circuit, the thickness of the superstructural surface comprising a sub-wavelength order; the first transparent electrode is used for receiving an incident light signal, the polarization direction of the incident light signal comprises a first direction and a second direction, the first direction is used for representing a direction parallel to a target intersection line, the target intersection line is used for representing an intersection line between a pixel array plane and a liquid crystal rotation plane, and the second direction is used for representing a direction perpendicular to the liquid crystal rotation plane; the super-structure surface is used for converting the polarization direction of the received optical signal with the polarization direction being the first direction into the second direction and converting the polarization direction of the received optical signal with the polarization direction being the second direction into the first direction; the driving circuit is used for configuring a target voltage, and the target voltage is used for representing the voltage between the first transparent electrode and the electrode layer; the liquid crystal box is used for adjusting the phase of the optical signal with the polarization direction being the first direction in the optical signals output by the first transparent electrode and the super-structure surface according to the target voltage.

In this application, the LCOS device includes an over-structured surface, where the over-structured surface may convert a polarization direction of an optical signal having a received polarization direction that is a first direction into a second direction, and convert a polarization direction of an optical signal having a received polarization direction that is a second direction into the first direction. The liquid crystal box can adjust the phase of the optical signal with the polarization direction being the first direction in the optical signals output by the first transparent electrode and the super-structure surface according to the target voltage. It follows that LCOS devices can perform polarization diversity processing and conversion processing on optical signals through the super-structured surface. The super-structured surface is simple in implementation mode, occupies small volume, reduces the complexity of equipment, reduces the construction cost of the equipment, and is more beneficial to realizing technical popularization.

In a possible implementation manner of the first aspect, the orientation or the size of the basic units in the super-structured surface is different for suppressing crosstalk signals, which include optical signals whose polarization states are not converted after passing through the super-structured surface.

In this possible implementation, to solve the problem of crosstalk due to residual light of unconverted polarization, an improvement can be achieved by a scheme of combined phase modulation of the super-structured surface and the liquid crystal cell. The basic idea of this possible implementation is to introduce different phases to the incident light by the arrangement of the orientation or dimensions of the elementary cells in the super-structured surface while polarization converting the incident light, so that the optical signal has a specific disturbance phase distribution. Then, a compensating phase distribution complementary to the disturbance phase distribution is introduced on the basis of the beam deflection phase by liquid crystal dynamic phase modulation, so that the disturbance phase and the compensating phase generated after the signal light subjected to normal polarization conversion is subjected to combined phase modulation between the super-structure surface and the liquid crystal box are mutually counteracted. Therefore, the optical signal with normal polarization conversion can keep the original light spot shape to deflect and be coupled to the output port. The interference light of unpolarized conversion and other diffraction orders cannot be completely counteracted due to different sensed phase modulation amounts, so that light spots are dispersed and cannot be efficiently coupled into an output port, and effective crosstalk suppression is realized.

In a possible implementation manner of the first aspect, the super-structured surface includes a first region and a second region, an angle between an orientation of a basic cell in the first region and the pixel array plane and an angle between an orientation of a basic cell in the second region and the pixel array plane are different, and the liquid crystal cell includes a third region and a fourth region; the first region is used for adding a first phase to the optical signals with the polarization directions of the first direction and the second direction after the polarization directions are converted

The second region is used for generating a polarization after converting the polarization directionThe vibration direction increases the first phase for the optical signals in the first direction and the second direction>

Said first phase->

And said second phase->

Different; the third region is used for adding a third phase to the optical signal which is output by the first transparent electrode and the first region and has the polarization direction of the first direction>

k is an integer; the fourth region is used for adding a fourth phase to the optical signal which is output by the first transparent electrode and the second region and has the polarization direction of the first direction>

k is an integer.

In this possible implementation, the orientation of the elementary units in the super-structured surface is indicative of the angle between the elementary units in the super-structured surface and the plane of the pixel array. If the orientations of the basic units in the first area and the second area are different, the polarization state of the signal a is not changed after passing through the first area, the polarization state of the signal B is not changed after passing through the second area, the disturbance phases and the compensation phases obtained by the crosstalk optical signal a and the crosstalk optical signal B which are not subjected to polarization conversion cannot be completely counteracted, and because the orientations of the basic units in the first area and the second area are different, the phase modulation amounts obtained by the crosstalk optical signal a and the crosstalk optical signal B are different, light spots are dispersed and cannot be efficiently coupled to port output, so that the suppression of the crosstalk signals is realized. In this possible implementation, the basic unit sizes in the super-structured surface are consistent, and the design and processing of the super-structured surface are easier to implement, thus reducing the processing cost of the LCOS device.

In a possible implementation manner of the first aspect, an angle between the orientation of the basic unit in the first area and the pixel array plane is 45 degrees, and an angle between the orientation of the basic unit in the second area and the pixel array plane is 135 degrees.

In this possible implementation manner, the angle between the orientation of the basic unit in the first area and the pixel array plane is 45 °, and the angle between the orientation of the basic unit in the second area and the pixel array plane is 135 °, so that the polarization conversion can be implemented while the phase modulations of 0 and pi are respectively introduced, and the possible implementation manner improves the suppression effect of the LCOS device on crosstalk signals.

In a possible implementation manner of the first aspect, the super-structured surface includes a first region and a second region, a size of a basic cell in the first region and a size of a basic cell in the second region are different, and the liquid crystal cell includes a third region and a fourth region; the first region is used for adding a first phase to the received optical signals with the polarization directions of the first direction and the second direction

The second region is used for adding a second phase to the received optical signals with the polarization directions of the first direction and the second direction >

Said first phase->

And said second phase->

Different; the third region is used for outputting the first transparent electrode and the first region with the polarization direction of the firstThe directional optical signal adds a third phase +.>

k is an integer; the fourth region is used for adding a fourth phase to the optical signal which is output by the first transparent electrode and the second region and has the polarization direction of the first direction

k is an integer.

In this possible implementation manner, if the sizes of the basic units in the first area and the second area are different, and the polarization state of the signal a is unchanged after passing through the first area, the polarization state of the signal B is unchanged after passing through the second area, the disturbing phases and compensating phases obtained by the crosstalk optical signal a and the crosstalk optical signal B which are not subjected to polarization conversion cannot be completely offset, and because the sizes of the basic units in the first area and the second area are different, the phase modulation amounts obtained by the crosstalk optical signal a and the crosstalk optical signal B are different, light spots are dispersed, so that the signals cannot be efficiently coupled to port output, and further the suppression of the crosstalk signals is realized. In this possible implementation, the degree of freedom of the LCOS device to set the perturbation phase can be improved by adjusting the size of the base unit to obtain different perturbation phases.

In a possible implementation manner of the first aspect, the electrode layer includes a metal electrode; the first surface of the liquid crystal box is covered with the first transparent electrode, and the second surface of the liquid crystal box is covered with the first surface of the super-structure surface; the second surface of the super-structured surface is covered on the first surface of the metal electrode; the second surface of the metal electrode is covered on the driving circuit; the metal electrode is used for reflecting the received optical signal.

In this possible implementation manner, a structure that an LCOS device may be implemented is provided, in this possible implementation manner, the super-structured surface may be directly processed on the conventional LCOS backplate, without changing the original backplate structure, so that the processing is relatively convenient, and the processing cost is saved.

In a possible implementation manner of the first aspect, the electrode layer includes a second transparent electrode and a metal plate; the first surface of the liquid crystal box is covered with the first transparent electrode, and the second surface of the liquid crystal box is covered with the first surface of the second transparent electrode; the second surface of the second transparent electrode covers the first surface of the super-structured surface; the second surface of the super-structured surface is covered on the first surface of the metal plate; the second surface of the metal plate is covered on the driving circuit; the metal plate is used for reflecting the received optical signals.

In this possible implementation, the super-structured surface is disposed outside the first transparent electrode and the second transparent electrode, avoiding the structural voltage division generated by the super-structured surface, and reducing the driving voltage of the LCOS device.

In a possible implementation manner of the first aspect, the electrode layer includes a second transparent electrode; the first surface of the liquid crystal box is covered with the first transparent electrode, and the second surface of the liquid crystal box is covered with the first surface of the second transparent electrode; the second surface of the second transparent electrode covers the first surface of the super-structured surface; the second surface of the super-structured surface is covered on the driving circuit; the super-structured surface is also configured to reflect the received optical signal.

In this possible implementation, the super-structured surface is disposed outside the first transparent electrode and the second transparent electrode, which avoids the structural voltage division generated by the super-structured surface, reduces the driving voltage of the LCOS device, and saves energy.

In a possible implementation manner of the first aspect, the material of the basic unit includes gold, silver, aluminum, platinum, chromium, silicon nitride, titanium dioxide or aluminum oxide.

In this possible implementation, if the material of the basic unit is a metal material, the thickness of the super-structure surface can be reduced, so as to reduce the structural partial pressure of the super-structure surface, and further reduce the driving voltage of the LCOS device. If the material of the base unit is a non-metallic material, the loss of the optical signal passing through the super-structured surface can be reduced.

In a possible implementation manner of the first aspect, the shape of the basic unit includes a polygonal column or an elliptic cylinder.

In the possible implementation manner, two possible implementation manners of the basic unit are provided, and the feasibility of the scheme is improved.

In one possible implementation of the first aspect, the super-structured surface further comprises a planarization material, the planarization material comprising silicon dioxide, aluminum oxide, silicon nitride, or silicon.

In this possible implementation manner, a possible implementation manner of the planarization material is provided, which improves the feasibility of the scheme.

In a possible implementation manner of the first aspect, the LCOS device further includes a passivation layer.

In this possible implementation, if the electrode in the electrode layer is a metal electrode, the passivation layer may protect the electrode activity and delay the electrode deactivation process. If the electrode in the electrode layer is a nonmetallic electrode, the passivation layer can further planarize the surface of the nonmetallic electrode.

A second aspect of the present application provides a wavelength selective switch WSS comprising an LCOS device as described in the first aspect or any one of the possible implementations of the first aspect.

The WSS provided in this application includes LCOS devices. The LCOS device comprises a super-structured surface, wherein the super-structured surface can convert the polarization direction of the received optical signal with the polarization direction being the first direction into the second direction and convert the polarization direction of the received optical signal with the polarization direction being the second direction into the first direction. The liquid crystal box can adjust the phase of the optical signal with the polarization direction being the first direction in the optical signals output by the first transparent electrode and the super-structure surface according to the target voltage. It follows that LCOS devices can perform polarization diversity processing and conversion processing on optical signals through the super-structured surface. The super-structured surface is simple in implementation, occupies a small volume inside the WSS, reduces the complexity of equipment, reduces the construction cost of the WSS, and is more beneficial to realizing technical popularization.

Drawings

Fig. 1 is a schematic structural diagram of a WSS provided in the present application;

FIG. 2 is a schematic illustration of a LCOS structure provided herein;

FIG. 3 is a schematic view of a liquid crystal cell according to the present application;

FIG. 4 is a schematic illustration of an application of an LCOS device provided herein;

FIG. 5 is a graph of polarization conversion efficiency for a super-structured surface provided herein;

FIG. 6 is a schematic diagram of a crosstalk signal provided herein;

FIG. 7 is a schematic view of a super-structured surface provided herein;

fig. 8 is a schematic diagram of the suppression effect of crosstalk signals provided in the present application;

FIG. 9 is a schematic view of another construction of a super-structured surface provided herein;

FIG. 10 is a graph of the suppression effect of another crosstalk signal provided herein;

FIG. 11 is a schematic diagram of another LCOS device provided herein;

FIG. 12 is a schematic illustration of another LCOS device provided herein;

fig. 13 is a schematic structural diagram of another LCOS device according to the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the embodiments of the present application will be described below with reference to the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. As a person of ordinary skill in the art can know, with the appearance of a new application scenario, the technical solution provided in the embodiment of the present application is applicable to similar technical problems.

The terms first, second and the like in the description and in the claims of the present application and in the above-described figures, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments described herein may be implemented in other sequences than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or modules is not necessarily limited to those steps or modules that are expressly listed or inherent to such process, method, article, or apparatus. The naming or numbering of the steps in the present application does not mean that the steps in the method flow must be executed according to the time/logic sequence indicated by the naming or numbering, and the execution sequence of the steps in the flow that are named or numbered may be changed according to the technical purpose to be achieved, so long as the same or similar technical effects can be achieved.

Liquid crystal on silicon (Liquid Crystal on Silicon, LCOS), is a miniaturized reflective active matrix liquid crystal display device or "microdisplay device". LCOS devices are also known as spatial light modulators. The top of the silicon substrate in LCOS devices is covered with a liquid crystal layer that modulates the light field. LCOS devices have the advantages of flexible light field control, repeatable erasing, high resolution, and the like, and therefore, LCOS devices are widely used in various fields.

In the conventional art, the material of the liquid crystal layer in LCOS devices is mainly nematic liquid crystal. Nematic liquid crystals are mainly composed of nonpolar rod-like liquid crystal molecules and have uniaxial crystal characteristics. In implementing optical field phase modulation, a conventional LCOS device is assumed to define a plane in which the LCOS device is located as an XY plane, and a normal direction of the XY plane is defined as a Z direction. In the XY plane, the orientation of the long axes of liquid crystal molecules under no voltage is defined as the X direction, and the direction orthogonal to both the X and Z directions is defined as the Y direction. When a voltage is applied to a conventional LCOS device, the orientation of the liquid crystal molecules can be rotated from the X-direction to the Z-direction. When the voltage is different, the orientation of the liquid crystal molecules is different in the angle of rotation from the X direction to the Z direction. Thus, the liquid crystal molecules at different voltages are oriented in different directions within the XZ plane. At this time, the incident light polarized in the X direction corresponds to the extraordinary light, and the refractive index thereof changes with the alignment of the liquid crystal molecules. Therefore, the incident light polarized in the X direction can be phase modulated by adjusting the voltage applied to the LCOS device while the thickness of the liquid crystal layer remains unchanged. The incident light polarized in the Y direction corresponds to ordinary light, and the refractive index thereof does not change with the orientation of the liquid crystal molecules, and phase modulation cannot be realized.

Aiming at the problems existing in the existing LCOS device, the application provides the LCOS device and the WSS, the super-structured surface in the LCOS device is simple in implementation mode, small in occupied volume, low in complexity of equipment, low in construction cost of the equipment and more beneficial to technical popularization.

The LCOS device and the WSS including the LCOS device provided herein will be described in detail with reference to the accompanying drawings, and the WSS provided herein will be described first.

Fig. 1 is a schematic structural diagram of a WSS provided in the present application.

Referring to fig. 1, in the present application, a device for optical signal routing in a reconfigurable optical add/drop multiplexer (ROADM) is a WSS, and the WSS shown in fig. 1 includes the LCOS provided in the present application. As shown in fig. 1, the WSS includes an input/output component, a dispersion component, a spot-transforming component, and an LCOS.

In this application, a schematic structural diagram of a WSS including LCOS is shown in fig. 1. After the input and output components receive the combined wave signals, the dispersion component can spatially separate the combined wave signal light emitted from the input port according to different wavelengths. The spot-transforming assembly can project the separated optical signals to different areas in the LCOS device. LCOS device deflects the optical signal through phase modulation to different incident light wavelength, and the optical signal after deflecting is transmitted to different output ports through facula transform subassembly and dispersion subassembly again to the optical signal of different wavelength selectivity route to the same or different output ports.

It can be appreciated that, alternatively, the LCOS device provided in the present application may be applied to WSS, where the LCOS device provided in the present application may also be applied to holographic display equipment, where the LCOS device provided in the present application may also be applied to laser radar devices, where the LCOS device provided in the present application may also be applied to other equipment, and is not limited herein.

The above examples describe the WSS provided herein, and the LCOS device provided herein will be described in detail below based on the WSS described above, with reference to the accompanying drawings.

Fig. 2 is a schematic structural diagram of an LCOS provided herein.

Referring to fig. 2, in the present application, an LCOS device 201 includes a first transparent electrode 301, a liquid crystal cell 302, an super-structure surface 303, an electrode layer 304, and a driving circuit 305, wherein the thickness of the super-structure surface includes a wavelength order or a sub-wavelength order.

The function of the various elements in an LCOS device is described in detail below.

In this application, the first transparent electrode 301 may receive an incident light signal, where the incident light signal may include light signals with various polarization directions, and the polarization directions of the incident light signal include a first direction and a second direction. The first direction is used for representing a direction parallel to a target intersection line, the target intersection line is used for representing an intersection line between a pixel array plane and a liquid crystal rotation plane, and the second direction is used for representing a direction perpendicular to the liquid crystal rotation plane.

In this application, the super-structure surface 303 may convert the polarization direction of the received optical signal having the polarization direction of the first direction into the second direction, and convert the polarization direction of the received optical signal having the polarization direction of the second direction into the first direction.

In this application, the driving circuit 305 may configure a target voltage, which is used to represent a voltage between the first transparent electrode 301 and the electrode layer 304.

In this application, the liquid crystal cell 302 may adjust the phase of the optical signal having the polarization direction of the first direction among the optical signals output from the first transparent electrode and the super-structure surface according to the target voltage.

First, a first direction and a second direction included in a polarization direction of an incident light signal received by a first transparent electrode in the present application will be exemplarily described as a specific example.

Fig. 3 is a schematic structural diagram of a liquid crystal cell provided in the present application.

As illustrated in fig. 3, the liquid crystal cell in the mainstream LCOS device currently mainly includes nematic liquid crystal composed of nonpolar rod-like liquid crystal molecules and having uniaxial crystal characteristics. For convenience of description, the plane in which the pixels in the liquid crystal cell lie is defined as the pixel array plane, i.e., XOY plane in the drawing. The normal to the XOY plane is defined as the Z direction, corresponding to the direction of application of the electric field. The orientation of the long axes of the liquid crystal molecules under no voltage is defined as the X direction, i.e., the first direction, and the direction orthogonal to both the X and Z directions is defined as the Y direction, i.e., the second direction. The XOZ plane is defined as the liquid crystal rotation plane when the liquid crystal molecular orientation can be rotated from the X direction to the Z direction by applying a voltage. The orientation of the liquid crystal molecules at different voltages along the XOZ plane corresponds to different birefringence conditions. At this time, the incident light polarized in the X direction corresponds to the extraordinary light, and the refractive index thereof changes with the orientation of the liquid crystal molecules, so that different phase modulation can be realized according to different voltages while the thickness of the liquid crystal molecules remains unchanged. The incident light polarized in the Y direction corresponds to ordinary light, and the refractive index of the incident light does not change with the orientation of the liquid crystal molecules, so that the phase modulation cannot be realized.

The operation of the LCOS provided herein will be described in one specific example with reference to the above examples.

Fig. 4 is a schematic diagram of an application of an LCOS device provided herein.

Referring to fig. 4, in the present application, after an optical signal a having a polarization direction X (first direction) passes through the first transparent electrode, the optical signal a first enters the liquid crystal cell. The liquid crystal molecules in the liquid crystal box are subjected to orientation change by the voltage between the first transparent electrode and the electrode layer, and as the X direction is parallel to the long axis orientation of the liquid crystal molecules, the liquid crystal molecules after orientation change can modulate the phase of an optical signal A polarized in the X direction, and a phase theta is applied to the signal A. Then, the signal a enters the super-structured surface, and the super-structured surface can perform polarization conversion on the signal a, and the polarization state of the signal a after polarization conversion is rotated by 90 ° and then becomes an optical signal polarized in the Y direction (second direction). The optical signal a polarized in the Y direction is reflected and then passes through the liquid crystal cell twice, and since the Y direction is perpendicular to the long axis alignment of the liquid crystal molecules, the liquid crystal molecules after the alignment change cannot modulate the phase of the optical signal a polarized in the Y direction, as shown in fig. 4. It follows that LCOS devices can phase modulate optical signal a in the X polarization direction.

In this application, after the optical signal a having the polarization direction of Y (second direction) passes through the first transparent electrode, it enters the liquid crystal cell for the first time. The liquid crystal molecules in the liquid crystal cell undergo orientation change due to the voltage between the first transparent electrode and the electrode layer, and the liquid crystal molecules after orientation change cannot modulate the phase of the optical signal a polarized in the Y direction because the Y direction is oriented perpendicular to the long axis of the liquid crystal molecules. Then, the signal a enters the super-structured surface, and the super-structured surface can perform polarization conversion on the signal a, and the polarization state of the signal a after polarization conversion is rotated by 90 ° and becomes an optical signal polarized in the X direction (first direction). The optical signal a polarized in the X direction is reflected and then passes through the liquid crystal cell twice, and since the X direction is parallel to the long axis alignment of the liquid crystal molecules, the liquid crystal molecules after the alignment change can modulate the phase of the optical signal a polarized in the X direction, as shown in fig. 4, and a phase θ is applied to the signal a. It follows that LCOS devices can phase modulate optical signal a in the Y polarization direction.

In summary, the same liquid crystal molecular phase modulation can be obtained once in the whole process from incidence to final emergence of the LCOS device for the X-polarized or Y-polarized incident light. An optical signal having any other polarization state in the incident light can always be decomposed into a combination of an optical component having an X-polarization state and an optical component having a Y-polarization state, and also only once liquid crystal molecular phase modulation is obtained, and thus the LCOS device has a polarization-independent phase response characteristic.

In this application, if the LCOS device is located between the first transparent electrode and the electrode layer, the thickness of the super-structured surface included in the LCOS device provided in this application may be far smaller than the thickness of the liquid crystal cell. Alternatively, the thickness of the super-structured surface may be slightly greater than the wavelength of the signal light received during operation, for example, the thickness of the super-structured surface may be 2.9 times the wavelength of the signal light, the thickness of the super-structured surface may be 1.5 times the wavelength of the signal light, and the thickness of the super-structured surface may be other values, which is not limited herein. The thickness of the super-structured surface may be smaller than the wavelength of the signal light, for example, the thickness of the super-structured surface may be 0.5 times the wavelength of the signal light, the thickness of the super-structured surface may be 0.1 times the wavelength of the signal light, and the thickness of the super-structured surface may also be other values, which is not limited herein. Because the thickness of the super-structured surface is far smaller than that of the liquid crystal layer, the super-structured surface does not generate obvious structural partial pressure, and the driving voltage of the LCOS device is prevented from being obviously increased. Alternatively, the thickness of the super-structured surface may be on the order of sub-wavelength, and the thickness of the super-structured surface may be other thickness, and is not limited herein.

The above examples illustrate the implementation manner and the working principle of the LCOS device provided in the present application, and in the present application, the LCOS device may further solve the problem of performance degradation caused by incomplete polarization conversion by suppressing crosstalk signals by arranging the orientations or dimensions of the basic cells in the super-structure surface. Specific implementations are described in detail in the examples below.

FIG. 5 is a graph of polarization conversion efficiency for a super-structured surface provided herein.

Referring to fig. 5, in the present application, due to wavelength dependence caused by material dispersion and errors in the actual device processing process, the super-structured surface cannot achieve a complete 100% polarization conversion efficiency in the full band, so there will inevitably be a part of residual optical signals with unpolarized conversion, and the crosstalk signal includes residual optical signals with unconverted polarization states after passing through the super-structured surface.

Fig. 6 is a schematic diagram of a crosstalk signal provided in the present application.

Referring to fig. 6, if the polarization state of the residual light without polarization conversion is X-direction (first direction), the phase modulation amount of the residual light is 2 times that of the normal polarization conversion light, so as to form +2-level crosstalk. If the polarization state of the residual light, in which no polarization conversion occurs, is in the Y direction (second direction), it is subjected to a phase modulation amount of 0, resulting in 0-level crosstalk. The residual light which is not subjected to polarization conversion has different propagation characteristics due to different phase modulation, thereby forming crosstalk light. In WSS, residual light that appears unpolarized converted can couple into other ports than the target port at different diffraction angles to form crosstalk, where typical crosstalk is that of the +2 diffraction order, while 0-order crosstalk is generally not transmitted as an output optical signal to the output port.

In this application, to solve the problem of crosstalk due to residual light of unconverted polarization, it is possible to improve by a scheme of combining phase modulation of the super-structured surface and the liquid crystal cell. The basic idea of this possible implementation is to introduce different phases to the incident light by the arrangement of the orientation or dimensions of the elementary cells in the super-structured surface while polarization converting the incident light, so that the optical signal has a specific disturbance phase distribution. Then, a compensating phase distribution complementary to the disturbance phase distribution is introduced on the basis of the beam deflection phase by liquid crystal dynamic phase modulation, so that the disturbance phase and the compensating phase generated after the signal light subjected to normal polarization conversion is subjected to combined phase modulation between the super-structure surface and the liquid crystal box are mutually counteracted. Therefore, the optical signal with normal polarization conversion can keep the original light spot shape to deflect and be coupled to the output port. For the crosstalk light of unpolarized conversion and other diffraction orders, the disturbance phase and the compensation phase cannot be completely counteracted due to different sensed phase modulation amounts, so that light spots are dispersed and cannot be efficiently coupled into an output port, and the crosstalk is effectively restrained.

Mode one: the orientation of the elementary cells in the super-structured surface is different to suppress crosstalk signals.

Fig. 7 is a schematic structural view of a super-structured surface provided in the present application.

Referring to fig. 7, in the present application, the super-structure surface includes a first region 401 and a second region 402, an angle between an orientation of a basic unit in the first region 401 and a pixel array plane is different from an angle between an orientation of a basic unit in the second region 402 and a pixel array plane, and the liquid crystal cell includes a third region 403 and a fourth region 404;

in the application, the first region can add a first phase to the optical signal whose polarization direction is the first direction and the second direction after the polarization direction is converted

The second region can add a first phase to the optical signal whose polarization direction is converted into the first direction and the second direction>

Wherein the first phase->

And second phase->

Are not identical. The third region can be opposite to the first regionThe optical signal with the polarization direction of the domain output being the first direction is added with a third phase +.>

k is an integer. The fourth region can add a fourth phase to the optical signal output from the second region with the polarization direction of the first direction>

k is an integer.

When the signal a is normally polarization-switched in the super-structured surface, the super-structured surface and the liquid crystal cell when jointly modulated have no effect on the normally polarization-switched optical signal a.

Illustratively, the first time an optical signal a having a polarization direction of X (first direction) enters the third region of the liquid crystal cell. Since the X direction is parallel to the long axis alignment of the liquid crystal molecules, the liquid crystal molecules after the alignment change can modulate the phase of the optical signal a polarized in the X direction, and a phase θ is applied to the signal a. In addition, a compensating phase is added to the optical signal A

The signal A modulated by the liquid crystal cell is applied +.>

The signal A modulated by the liquid crystal box enters a first area of the super-structure surface, and the super-structure surface can perform polarization conversion on the signal A to obtain a signal A polarized in the Y direction. In addition, the super-structured surface can modulate the phase of the signal A, adding an additional phase to the signal A>

The phase of the signal A modulated by the liquid crystal cell and the super-structured surface is applied +.>

The optical signal A polarized in the Y direction passes through the liquid crystal box for a second time after being reflected, and the liquid crystal molecules with changed orientation are aligned vertically to the long axes of the liquid crystal molecules in the Y directionThe phase of the optical signal a polarized in the Y direction cannot be modulated. It can be seen that the combination of the super-structured surface and the liquid crystal cell has no effect on the normally polarization-switched X-polarized light signal a.

Illustratively, the first time an optical signal a having a polarization direction of Y (second direction) enters the third region of the liquid crystal cell. Since the Y direction is perpendicular to the long axis alignment of the liquid crystal molecules, the liquid crystal molecules after the alignment change cannot modulate the phase of the optical signal a polarized in the Y direction. The signal A after passing through the liquid crystal box enters a first area of the super-structure surface, and the super-structure surface can perform polarization conversion on the signal A to obtain an X-direction polarized signal A. In addition, the super-structured surface can modulate the phase of the signal A and add an additional phase to the signal A

The optical signal A polarized in the X direction passes through the liquid crystal box for a second time after being reflected, and the liquid crystal molecules with changed orientation can modulate the phase of the optical signal A polarized in the X direction and apply a phase theta to the signal A because the Y direction is parallel to the long axis orientation of the liquid crystal molecules. In addition, a compensating phase is added to the optical signal A>

The phase of the signal A modulated by the super-structured surface and the liquid crystal cell is applied +.>

It can be seen that the combination of the super-structured surface and the liquid crystal cell has no effect on the normally polarization-switched Y-polarized optical signal a.

When the polarization conversion of the signal a in the super-structured surface is abnormal, the super-structured surface and the liquid crystal cell have an influence on the optical signal a which is not normally polarization-converted when they are modulated in combination.

Illustratively, the first time an optical signal a having a polarization direction of X (first direction) enters the third region of the liquid crystal cell. Since the X direction is parallel to the long axis alignment of the liquid crystal molecules, the liquid crystal molecules after the alignment change can modulate the phase of the optical signal a polarized in the X direction, and a phase θ is applied to the signal a. In addition, will also pairThe optical signal A is added with a compensation phase

The signal A modulated by the liquid crystal cell is applied +.>

And the signal A modulated by the liquid crystal box enters a first area of the super-structure surface, and if the super-structure surface does not carry out polarization conversion on the signal A, the super-structure surface does not modulate the phase of the signal A. After the optical signal A polarized in the X direction is reflected and passes through the liquid crystal box for the second time, the liquid crystal molecules with changed orientation apply a phase theta to the phase of the optical signal A polarized in the X direction which enters the liquid crystal box for the second time, and a compensation phase is added to the optical signal A >

The phase of the signal A modulated twice by the liquid crystal cell is applied as +.>

Similarly, when the optical signal B with the polarization direction of X (first direction) enters the fourth region and the second region passes through the fourth region, the phase of the signal A modulated by the liquid crystal cell is ∈>

Illustratively, the first time an optical signal a having a polarization direction of Y (second direction) enters the third region of the liquid crystal cell. Since the Y direction is perpendicular to the long axis alignment of the liquid crystal molecules, the liquid crystal molecules after the alignment change cannot modulate the phase of the optical signal a polarized in the Y direction. The signal a enters the first region of the super-structured surface, and if the super-structured surface does not perform polarization conversion on the signal a, the super-structured surface does not modulate the phase of the signal a. The optical signal A polarized in the Y direction passes through the liquid crystal box twice after being reflected, and the phase applied to the signal A by the liquid crystal box and the super-structure surface is 0.

Similarly, when the optical signal B having the polarization direction Y (second direction) enters the fourth region and the second region passes through the fourth region, the phase of the signal a modulated by the liquid crystal cell is 0. And the 0-level crosstalk is not generally transmitted to the output port as an output optical signal. And therefore does not affect the signal transmission.

Fig. 8 is a schematic diagram of an effect of suppressing crosstalk signals provided in the present application.

In this application, the orientation of the elementary units in the super-structured surface means the angle between the elementary units in the super-structured surface and the plane of the pixel array. If the orientations of the basic units in the first area and the second area are different, the polarization state of the signal a is not changed after passing through the first area, the polarization state of the signal B is not changed after passing through the second area, the disturbance phases and the compensation phases obtained by the unpolarized crosstalk optical signal a and the crosstalk optical signal B cannot be completely cancelled, and because the orientations of the basic units in the first area and the second area are different, the phase modulation amounts obtained by the crosstalk optical signal a and the crosstalk optical signal B are different, so that light spots are dispersed and cannot be efficiently coupled to the port output. As in fig. 8, suppression of crosstalk signals is further achieved.

In this application, the orientation of the base units in the first and second regions may alternatively be at any angle, wherein. The orientation of the base unit in the first region may be at an angle of 45 ° to the plane of the pixel array and the orientation of the base unit in the second region may be at an angle of 135 ° to the plane of the pixel array. Alternatively, the included angle between the basic unit and the pixel array plane may be other angles, which is not limited herein.

Mode two: the size of the elementary cells in the super-structured surface is different to suppress crosstalk signals.

Fig. 9 is a schematic structural view of a super-structured surface provided in the present application.

Referring to fig. 9, in the present application, the super-structure surface includes a first region 501 and a second region 502, the size of the basic cell in the first region 501 is different from the size of the basic cell in the second region 502, and the liquid crystal cell includes a third region 503 and a fourth region 504.

In the present application, the first region 501 is dockedThe received optical signal with the polarization direction of the first direction and the second direction increases the first phase

Second region 502 adds a second phase to the received optical signal having the first and second directions of polarization>

First phase->

And second phase->

Are not identical. Third region 503 adds a third phase to the optical signal output from the first region and having the polarization direction of the first direction>

k is an integer. The fourth region 504 adds a fourth phase to the optical signal output from the second region with the polarization direction of the first direction>

k is an integer.

The signal A modulated by the liquid crystal cell is applied +.>

The optical signal a polarized in the Y direction is reflected and then passes through the liquid crystal cell twice, and since the Y direction is oriented perpendicular to the long axis of the liquid crystal molecule, the liquid crystal molecule after the orientation change cannot modulate the phase of the optical signal a polarized in the Y direction. It can be seen that the combination of the super-structured surface and the liquid crystal cell has no effect on the normally polarization-switched X-polarized light signal a.

Modulated by super-structured surfaces and liquid crystal cellsThe phase of signal A applied is +.>

The signal A modulated by the liquid crystal cell is applied +.>

The signal A modulated by the liquid crystal box enters a first area of the super-structure surface, and if the super-structure surface does not carry out polarization conversion on the signal A, the super-structure surface still adds a disturbance phase +_for the signal A >

After the optical signal A polarized in the X direction is reflected and then passes through the liquid crystal box for the second time, the liquid crystal molecules with changed orientation apply a phase theta to the phase of the optical signal A polarized in the X direction which enters the liquid crystal box for the second time, and a compensation phase is added to the optical signal A

Similarly, after the optical signal B having the polarization direction X (the first direction) enters the fourth region and the second region passes through the fourth region, the first region and the second region have different disturbance phases for the signal A, B due to different sizes of the basic units, and accordingly, the third region and the fourth region in the liquid crystal cell have different compensation phases for the signal A, B. The phase of the signal B modulated twice by the liquid crystal cell is applied as +.>

Illustratively, the first time an optical signal a having a polarization direction of Y (second direction) enters the third region of the liquid crystal cell. Since the Y direction is perpendicular to the long axis alignment of the liquid crystal molecules, the liquid crystal molecules after the alignment change cannot modulate the phase of the optical signal a polarized in the Y direction. The signal A enters the first area of the super-structure surface, and if the super-structure surface does not perform polarization conversion on the signal A, the super-structure surface still applies a disturbance phase to the phase of the signal A

The optical signal A polarized in the Y direction passes through the liquid crystal box for a second time after being reflected, the phase of the signal A applied by the liquid crystal box is 0, and the phase of the signal A applied after the liquid crystal box and the super-structure surface act together is +.>

Similarly, when the optical signal B with the polarization direction Y (second direction) enters the fourth region and the second region passes through the fourth region, the first region and the second region have different dimensions of the basic units, so that the disturbance phases of the first region and the second region added to the signal A, B are different, and the modulated signal B is applied with a phase of

Fig. 10 is a schematic diagram of another suppression effect of crosstalk signals provided in the present application.

As shown in fig. 10, if the sizes of the basic units in the first area and the second area are different, and the polarization state of the signal a is not changed after passing through the first area, and the polarization state of the signal B is not changed after passing through the second area, the disturbance phases and the compensation phases obtained by the crosstalk optical signal a and the crosstalk optical signal B which are not polarization-converted cannot be completely cancelled, and because the sizes of the basic units in the first area and the second area are different, the phase modulation amounts obtained by the crosstalk optical signal a and the crosstalk optical signal B are different, so that light spots are dispersed and cannot be efficiently coupled to the port output, and further, the suppression of the crosstalk signal is realized. In this possible implementation, the degree of freedom of the LCOS device to set the perturbation phase can be improved by adjusting the size of the base unit to obtain different perturbation phases.

The foregoing examples illustrate various applications of LCOS devices, and the following examples will illustrate in detail possible implementation configurations of LCOS devices provided herein in connection with the accompanying drawings.

Structure one:

fig. 11 is a schematic structural diagram of another LCOS device according to the present application.

Referring to fig. 11, the electrode layer may further include a metal electrode 306.

In this application, a first surface of the liquid crystal cell 302 is covered with a first transparent electrode 301, and a second surface of the liquid crystal cell 302 is covered with a first surface of the super-structured surface 303. The second side of the super-structured surface 303 overlies the first side of the metal electrode 306. The second surface of the metal electrode 306 covers the driving circuit 305. Wherein the metal electrode 306 may reflect the received optical signal, i.e. the metal electrode 306 may reflect the optical signal output by the super-structured surface 303.

In the possible implementation mode, the super-structured surface can be directly processed on the traditional LCOS backboard, the original backboard structure is not required to be changed, the processing is more convenient, and the processing cost is saved.

And (2) a structure II:

fig. 12 is a schematic structural diagram of another LCOS device according to the present application.

Referring to fig. 12, in the present application, the electrode layer includes a second transparent electrode 307 and a metal plate 308.

In this application, the first surface of the liquid crystal cell 302 is covered with the first transparent electrode 301, and the second surface of the liquid crystal cell 302 is covered with the first surface of the second transparent electrode 307. The second surface of the second transparent electrode 307 overlies the first surface of the super-structured surface 303. The second side of the super-structured surface 303 overlies the first side of the metal plate 308. The second surface of the metal plate 308 covers the driving circuit 305. The metal plate 308 may reflect the received optical signal, i.e. the metal plate 308 may reflect the optical signal output by the super-structured surface 303.

And (3) a structure III:

Referring to fig. 13, in the present application, the electrode layer may optionally include a second transparent electrode 307.

In this application, the first surface of the liquid crystal cell 302 is covered with the first transparent electrode 301, and the second surface of the liquid crystal cell 302 is covered with the first surface of the second transparent electrode 307. The second surface of the second transparent electrode 307 overlies the first surface of the super-structured surface 303. The second side of the super-structure surface 303 is covered by the driving circuit 305. The super-structured surface 303 may also reflect the received optical signal.

In the implementation described in structure two and structure three, the super-structured surface 303 is disposed outside the first transparent electrode 301 and the second transparent electrode 307, which avoids the structural voltage division generated by the super-structured surface 303 and reduces the driving voltage of the LCOS device.

It is understood that the LCOS device provided in the present application may have other structures besides the above three possible implementations, and is not limited thereto.

In this application, the super-structured surface includes a basic unit, and optionally, a material of the basic unit may include gold, silver, aluminum, platinum, chromium, silicon nitride, titanium dioxide, or aluminum oxide, and a material of the basic unit may further include other materials, which is not limited herein.

In this application, the shape of the basic unit may alternatively include a polygonal column or an elliptic column, and the shape of the basic unit may also be other shapes such as a cube, which is not limited herein.

In this application, optionally, the super-structured surface may further include a planarization material, where the basic unit is included in the planarization material, and the planarization material may include silicon dioxide, aluminum oxide, silicon nitride, or silicon, and the planarization material may further include other materials, which is not limited herein.

The WSS and LCOS devices provided herein have been described in detail, with specific examples being employed herein to illustrate the principles and embodiments of the present application, the above examples being provided only to assist in understanding the methods and core ideas of the present application. Meanwhile, as those skilled in the art will have modifications in the specific embodiments and application scope in accordance with the ideas of the present application, the present description should not be construed as limiting the present application in view of the above.

Claims

1. A liquid crystal on silicon LCOS device, comprising a first transparent electrode, a liquid crystal cell, an ultra-structured surface, an electrode layer and a drive circuit, wherein the thickness of the ultra-structured surface comprises a wavelength order or a sub-wavelength order;

the first transparent electrode is used for receiving an incident light signal, the polarization direction of the incident light signal comprises a first direction and a second direction, the first direction is used for representing a direction parallel to a target intersection line, the target intersection line is used for representing an intersection line between a pixel array plane and a liquid crystal rotation plane, and the second direction is used for representing a direction perpendicular to the liquid crystal rotation plane;

the super-structure surface is used for converting the polarization direction of the received optical signal with the polarization direction being the first direction into the second direction and converting the polarization direction of the received optical signal with the polarization direction being the second direction into the first direction;

The driving circuit is used for configuring a target voltage, and the target voltage is used for representing the voltage between the first transparent electrode and the electrode layer;

the liquid crystal box is used for adjusting the phase of the optical signal with the polarization direction being the first direction in the optical signals output by the first transparent electrode and the super-structure surface according to the target voltage.

2. The LCOS device of claim 1, wherein the orientation or size of the base cells in the super-structured surface is different for suppressing crosstalk signals, the crosstalk signals comprising optical signals whose polarization state is not converted after passing through the super-structured surface.

3. The LCOS device of claim 2, wherein said super-structured surface comprises first and second regions, wherein the orientation of the base cells in said first region is different from the angle of the plane of said pixel array and the orientation of the base cells in said second region is different from the angle of the plane of said pixel array, and wherein said liquid crystal cell comprises third and fourth regions;

the first region is used for adding a first phase to the optical signals with the polarization directions of the first direction and the second direction after the polarization directions are converted

The second region is used for adding a first phase to the optical signals with the polarization directions of the first direction and the second direction after the polarization direction is converted

Said first phase->

And said second phase->

Different;

the third region is used for adding a third phase to the optical signal which is output by the first transparent electrode and the first region and has the polarization direction of the first direction

k is an integer;

the fourth region is used for adding a fourth phase to the optical signal which is output by the first transparent electrode and the second region and has the polarization direction of the first direction

k is an integer.

4. The LCOS device as recited in claim 3, wherein the angle between the orientation of the base cells in said first region and the plane of said pixel array is 45 degrees and the angle between the orientation of the base cells in said second region and the plane of said pixel array is 135 degrees.

5. The LCOS device according to claim 2, wherein said super-structured surface comprises a first region and a second region, the size of the base cells within said first region being different from the size of the base cells within said second region, said liquid crystal cell comprising a third region and a fourth region;

The first region is used for adding a first phase to the received optical signals with the polarization directions of the first direction and the second direction

The second region is used for adding a second phase to the received optical signals with the polarization directions of the first direction and the second direction

Said first phase->

And said second phase->

Different;

k is an integer;

k is an integer.

6. The LCOS device according to any one of claims 1 to 5, wherein said electrode layer comprises a metal electrode;

the first surface of the liquid crystal box is covered with the first transparent electrode, and the second surface of the liquid crystal box is covered with the first surface of the super-structure surface;

the second surface of the super-structured surface is covered on the first surface of the metal electrode;

the second surface of the metal electrode is covered on the driving circuit;

The metal electrode is used for reflecting the received optical signal.

7. The LCOS device according to any one of claims 1 to 5, wherein said electrode layer comprises a second transparent electrode and a metal plate;

the first surface of the liquid crystal box is covered with the first transparent electrode, and the second surface of the liquid crystal box is covered with the first surface of the second transparent electrode;

the second surface of the second transparent electrode covers the first surface of the super-structured surface;

the second surface of the super-structured surface is covered on the first surface of the metal plate;

the second surface of the metal plate is covered on the driving circuit;

the metal plate is used for reflecting the received optical signals.

8. The LCOS device according to any one of claims 1-5, wherein said electrode layer comprises a second transparent electrode;

the second surface of the super-structured surface is covered on the driving circuit;

the super-structured surface is also configured to reflect the received optical signal.

9. The LCOS device as recited in any one of claims 2 to 8, wherein the material of the base unit comprises gold, silver, aluminum, platinum, chromium, silicon nitride, titanium dioxide or aluminum oxide.

10. The LCOS device as recited in any one of claims 2 to 9, wherein the shape of said base unit comprises a polygonal or elliptical cylinder.

11. The LCOS device as recited in any one of claims 2-10, wherein the super-structured surface further comprises a planarization material comprising silicon dioxide, aluminum oxide, silicon nitride or silicon.

12. A wavelength selective switch WSS, characterized in that the WSS comprises therein an LCOS device according to any one of the preceding claims 1 to 11.