CN115167057A

CN115167057A - Transmission-type two-dimensional liquid crystal spatial light modulator

Info

Publication number: CN115167057A
Application number: CN202210718003.3A
Authority: CN
Inventors: 贺晓娴; 汪相如; 李鸣凤; 谭庆贵
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2022-06-22
Filing date: 2022-06-22
Publication date: 2022-10-11

Abstract

The invention discloses a transmission-type two-dimensional liquid crystal spatial light modulator, which is applied to the technical field of liquid crystal spatial light modulators and liquid crystal optoelectronic devices and aims at solving the problems that when the two-dimensional deflection is realized through device cascade in the prior art, a half wave plate is usually additionally added between two phased arrays to switch the polarization direction of incident light, so that the device cascade not only can introduce system insertion loss and restrict the radiation efficiency of an antenna, but also can increase the thickness of a component and the control complexity of the system; according to the invention, the substrate with double surfaces plated with the ITO film layers is used, two ITO layers are photoetched into patterns with mutually vertical array electrodes, the vertical deflection and the horizontal deflection of incident laser are respectively controlled, and the two-dimensional deflection of transmission laser is controlled by using a single device.

Description

Transmission-type two-dimensional liquid crystal spatial light modulator

Technical Field

The invention belongs to the technical field of liquid crystal spatial light modulators and liquid crystal optoelectronic devices, and particularly relates to a light modulator.

Background

The beam pointing control module is a very important component of many laser applications. The beam pointing control method comprises a mechanical control mode and a non-mechanical control mode. The mechanical light beam pointing scheme adopts a mode of a mechanical turntable and a fixed lens, and although the optical design and control scheme is mature, the scanning speed is high, the field range is wide, the mechanical light beam pointing scheme has the defects of beam pointing conversion inertia, large and heavy volume, difficulty in conforming to a system, incapability of forming multiple beams and the like, and has great limitation in practical application. Liquid crystal spatial light modulators, as a non-mechanical spatial laser modulator with many advantages, have important applications in the fields of laser communication, laser radar, laser weapons, and the like. The liquid crystal spatial light modulator utilizes the electric control birefringence effect of a liquid crystal material, changes the refractive index distribution of liquid crystal through a complex control algorithm design, and realizes the distributed regulation and control of the laser near-field phase. Similar to the microwave phased array, the laser modulated by the liquid crystal spatial light modulator is shaped again after being coherent in a far field, and the purposes of self-defining the beam direction, the number of beams, the beam energy and the like can be realized.

The beam control and beam shaping in two-dimensional directions are requirements of numerous application fields on a spatial light modulator, and at present, two-dimensional liquid crystal spatial light modulation devices are all silicon-based reflective devices and are manufactured by adopting a semiconductor manufacturing process. However, the system optical path design and control algorithm of the reflective device are complex, and there is a certain limitation in practical application. The transmissive liquid crystal spatial light modulators are all one-dimensional deflection devices, two-dimensional deflection needs to be achieved through device cascading in an actual application scene, and a half wave plate needs to be additionally added between two phased arrays to switch the polarization direction of incident light when the devices are cascaded. Device cascading not only introduces system insertion loss, limits antenna radiation efficiency, but also increases component thickness and system control complexity.

Disclosure of Invention

In order to solve the technical problem, the invention provides a transmission type two-dimensional liquid crystal spatial light modulator, which is characterized in that a substrate with double surfaces plated with ITO film layers is used without changing the structure of the original transmission type spatial light modulator, two ITO layers are photoetched into patterns with mutually vertical array electrodes, the vertical deflection and the horizontal deflection of incident laser are respectively controlled, and the purpose of controlling the two-dimensional deflection of the transmission laser by using a single device is realized.

The technical scheme adopted by the invention is as follows: a transmissive two-dimensional liquid crystal spatial light modulator comprising, in order from top to bottom: the liquid crystal display panel comprises a first glass substrate, a first ITO-COM electrode, a first PI orientation film, a first liquid crystal molecular layer, a second PI orientation film, a first ITO array electrode layer, a second glass substrate, a second ITO array electrode layer, a third PI orientation film, a second liquid crystal molecular layer, a fourth PI orientation film, a second ITO-COM electrode and a third glass substrate.

Furthermore, the electrode period directions of the first ITO array electrode layer and the second ITO array electrode layer are mutually vertical, the vertical deflection and the horizontal deflection of incident laser are respectively controlled, and the two-dimensional deflection of the laser is controlled by using a single device.

Furthermore, the first ITO array electrode layer and the second ITO array electrode layer are aligned through Mark points, and the number, the position and the size of the Mark points can be adjusted according to the positions and the sizes of the array electrodes and the driving ICs.

Furthermore, the first ITO array electrode layer and the second ITO array electrode layer are obtained by photoetching the front surface and the back surface of the second glass substrate.

Further, the first liquid crystal layer and the second liquid crystal layer have the same size and completely cover the array electrode area.

Further, the first liquid crystal layer and the second liquid crystal layer have the same structure and both comprise spacers at two ends and liquid crystal molecules filled in the middle.

Further, the first PI alignment film, the second PI alignment film, the third PI alignment film, and the fourth PI alignment film have the same alignment direction, and can perform continuous two-dimensional deflection modulation on laser light having the same polarization direction as the alignment direction.

The invention has the beneficial effects that: the transmission type two-dimensional liquid crystal spatial light modulator can be used for preparing a transmission type two-dimensional liquid crystal optical phased array device by using three glass substrates and two liquid crystal molecular layers on the basis of not changing the structure of the original transmission type optical device; the device can perform two-dimensional deflection control on the laser in a single polarization direction, does not need device cascade connection and a half wave plate, and can reduce system insertion loss.

Drawings

FIG. 1 is a schematic diagram of a transmissive two-dimensional liquid crystal spatial light modulator of the present invention;

FIG. 2 is a schematic longitudinal sectional view of a transmissive two-dimensional liquid crystal spatial light modulator of the present invention;

FIG. 3 is a schematic diagram showing the electrode distribution on both sides A and B of the second glass substrate of the transmissive two-dimensional liquid crystal spatial light modulator according to the present invention;

wherein, (a) is A area array electrode pattern, (B) is B area array electrode pattern, (c) is the schematic diagram after AB two sides are aligned;

description of the reference numerals: 1 is a first cover plate substrate plated with a single-layer ITO film; 2 is a substrate with double-sided photoetching patterns; 3 is a second cover plate substrate plated with a single-layer ITO film; 4-a first glass substrate; 5,15 is an ITO-COM electrode, 6,8,12,14 is a PI orientation layer, 7,13 is a liquid crystal molecular layer, 9,11 is an ITO array electrode layer, 10 is a second glass substrate, 16 is a third glass substrate.

Detailed Description

In order to facilitate the understanding of the technical contents of the present invention by those skilled in the art, the present invention will be further explained with reference to the accompanying drawings.

As shown in fig. 1, a transmissive two-dimensional liquid crystal spatial light modulator includes a first cover substrate 1, a substrate 2 having a double-sided lithographic pattern, and a second cover substrate 3. The structure of the first cover substrate 1 specifically includes: a first glass substrate 4 and an ITO thin film 5 which is plated below (surface B) the glass substrate 4 and is used as a COM electrode; the upper and lower AB two sides of the substrate 2 are plated with

ITO films

9,11, and are photoetched into patterns with mutually vertical array electrodes, and the structure of the second cover plate substrate 3 specifically comprises: a second glass substrate 10 and an ITO thin film 15 as a COM electrode plated on the upper side (surface A) of the second glass substrate 10.

Fig. 2 shows a schematic longitudinal section of the device, which specifically includes: the liquid crystal display panel comprises a first glass substrate 4, an ITO-COM electrode 5, a PI orientation film 6, a spacer 7, a liquid crystal molecular layer 8, a PI orientation film 9, an ITO array electrode layer 10, a second glass substrate 11, an ITO array electrode layer 12, a PI orientation film 13, a spacer 14, a liquid crystal molecular layer 15, a PI orientation film 16, an ITO-COM electrode 17 and a third glass substrate 18.

As shown in FIG. 2, the structure of the prior transmission-type spatial light modulator is not changed, two ITO layers are photoetched into patterns with mutually vertical array electrodes by using a substrate with two sides coated with ITO film layers, the vertical deflection and the horizontal deflection of incident laser are respectively controlled, and the two-dimensional deflection of the transmission laser is controlled by using a single device. The orientation directions of the four layers of PI orientation films in FIG. 2 are all the same, and two-dimensional deflection modulation can be performed on laser with the same polarization direction and orientation direction, without adding a half wave plate in the middle. The two liquid crystal molecule layers in fig. 2 have the same thickness to ensure that the additional phase of the incident light caused by the rotation of the liquid crystal molecules under the same voltage is the same. The same spacer dimensions are used to control the same cell thickness. The first glass substrate and the second glass substrate are attached to each other, and the third glass substrate and the second glass substrate are attached to each other at the same time, so that the device is formed in one step, and the hot pressing process is prevented from causing secondary influence on the frame glue and the spacers.

The two liquid crystal molecular layers have the same size and completely cover the array electrode area.

As shown in fig. 3, the electrode distribution of the transmissive two-dimensional liquid crystal spatial light modulator on both surfaces a and B of the second glass substrate is schematically shown, and the electrode pattern of the a-plane array is the same as that of the B-plane array, and the a-plane array is rotated by 90 ° in physical position. The A surface electrode loads voltage with the horizontal direction as a period to the liquid crystal and controls the deflection of the laser in the horizontal direction; the B-plane electrode loads voltage with the period of vertical direction to the liquid crystal to control the deflection of the laser in the vertical direction. As shown in fig. 3, the array electrodes are provided with male and female marks around them for alignment of the AB surfaces during photolithography, and the positions and sizes of the Mark points can be adjusted according to the positions and sizes of the array electrodes and the driving IC. When designing the device, it is necessary to ensure that the aligned pattern does not block the driver IC, as shown in fig. 3 (c), so as to prevent the subsequent IC bonding process from causing problems.

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A transmissive two-dimensional liquid crystal spatial light modulator comprising, in order from top to bottom: the liquid crystal display panel comprises a first glass substrate, a first ITO-COM electrode, a first PI orientation film, a first liquid crystal layer, a second PI orientation film, a first ITO array electrode layer, a second glass substrate, a second ITO array electrode layer, a third PI orientation film, a second liquid crystal layer, a fourth PI orientation film, a second ITO-COM electrode and a third glass substrate;

the electrode period directions of the first ITO array electrode layer and the second ITO array electrode layer are mutually vertical.

2. A transmissive two dimensional liquid crystal spatial light modulator according to claim 1 wherein said first ITO array electrode layer is aligned with said second ITO array electrode layer by Mark dots.

3. A transmissive two-dimensional liquid crystal spatial light modulator according to claim 2 wherein the first ITO array electrode layer and the second ITO array electrode layer are formed by photolithography on both sides of the second glass substrate.

4. A transmissive two dimensional liquid crystal spatial light modulator according to claim 1 wherein the first liquid crystal layer and the second liquid crystal layer are the same size and completely cover the array electrode area.

5. A transmissive two-dimensional liquid crystal spatial light modulator according to claim 4 wherein the first liquid crystal layer and the second liquid crystal layer are identical in structure and each comprises spacers at two ends and liquid crystal molecules filled in the middle.

6. The transmissive two-dimensional liquid crystal spatial light modulator of claim 1, wherein the first PI alignment film, the second PI alignment film, the third PI alignment film and the fourth PI alignment film have the same alignment direction.