Quick response liquid crystal optical phased array device

Abstract

The invention discloses a quick-response liquid crystal optical phased array device. The quick-response liquid crystal optical phased array device at least comprises two liquid crystal optical phased array device units, each liquid crystal optical phased array device unit has the same structure and sequentially comprises a first glass substrate layer, a common electrode layer, a first orientation layer, a liquid crystal layer, a second orientation layer, an array electrode layer and a second glass substrate layer; the orientation directions of the first orientation layer and the second orientation layer are consistent, the liquid crystal layer is located between the first orientation layer and the second orientation layer, the liquid crystal layer is a stress polymer network liquid crystal layer, and the molecular director direction of the liquid crystal layer is consistent with the orientation direction of the first orientation layer; the array electrode layer is of a one-dimensional electrode array structure composed of a plurality of strip-shaped electrodes, the strip-shaped electrodes are insulated from one another, and the voltage of each strip-shaped electrode is independently controlled; the common electrode layer and the array electrode layer are used in pairs to form a voltage difference which is used for controlling the arrangement state of liquid crystal molecules in each electrode array unit area.

Description

Technical Field

[0001] The invention relates to the technical field of liquid crystal optical phased arrays, and in particular to a fast-response liquid crystal optical phased array device. Background Art

[0002] In free-space laser optical communications, laser sensing, and laser radar applications, high-precision capture, tracking, and targeting (ATP) of laser beams is a very important key technology and difficulty. Traditional ATP solutions usually use mechanical methods such as universal joints. Due to factors such as large size, heavy weight, high power consumption, and mechanical wear, non-mechanical ATP technology has gradually attracted attention. Currently, the commonly used non-mechanical beam scanning adjustment and control methods mainly include microlens array technology, MEMS (micro-electromechanical system) technology, electrowetting microprism technology, and liquid crystal optical phased array technology.

[0003] Among them, liquid crystal optical phased array (LCOPA) is a programmable phase control device, which usually uses nematic liquid crystal as the electro-optical material for phase modulation, so that the device has unique advantages such as small size, light weight, low power consumption, and easy to combine with microelectronic control circuits. However, the existing liquid crystal optical phased array devices using nematic liquid crystal materials have a response time of about 10ms in the near-infrared band, and the response speed decreases rapidly in the mid-infrared and far-infrared bands. To solve this problem, in the prior art, polymer network liquid crystal PNLC is used to improve the response speed of liquid crystal, and an array-shaped device with a multi-channel electrode structure is manufactured. However, the device has few driving channels and low integration, which cannot meet the actual application requirements. Summary of the invention

[0004] Purpose of the invention: In order to solve the problem of slow response speed of existing liquid crystal phased array devices, the present invention proposes a fast response liquid crystal optical phased array device structure.

[0005] Technical solution: A fast-response liquid crystal optical phased array device, comprising at least two liquid crystal optical phased array device units;

[0006] Each liquid crystal optical phased array device unit has the same structure, and includes in sequence: a first glass substrate layer, a common electrode layer, a first orientation layer, a liquid crystal layer, a second orientation layer, an array electrode layer, and a second glass substrate layer; the first glass substrate layer and the second glass substrate layer serve as substrates of the liquid crystal optical phased array device unit;

[0007] The first alignment layer and the second alignment layer have the same orientation direction, the liquid crystal layer is located between the first alignment layer and the second alignment layer, the liquid crystal layer is a stress polymer network liquid crystal layer, and the direction of its molecular director is consistent with the orientation direction of the first alignment layer; the array electrode layer is a one-dimensional electrode array structure composed of a plurality of strip electrodes, each strip electrode is an electrode array unit, and there is a spacing between two adjacent strip electrodes so that the strip electrodes are insulated, and the voltage of each strip electrode is independently controlled;

[0008] The common electrode layer and the array electrode layer are used in pairs to form a voltage difference, which is used to control the arrangement state of liquid crystal molecules in each electrode array unit area.

[0009] Furthermore, the second glass substrate layer of one liquid crystal optical phased array device unit is bonded to the second glass substrate layer of another liquid crystal optical phased array device unit by optical glue, and the refractive index of the optical glue is consistent with the refractive index of the glass substrate layer of the liquid crystal optical phased array device unit.

[0010] Furthermore, the first alignment layer and the second alignment layer are rubbed alignment agent layers or photo-alignment agent layers.

[0011] Furthermore, the stress polymer network liquid crystal layer is prepared according to the following steps:

[0012] Mix the materials in the following ratio: nematic liquid crystal material 5CB: photosensitive polymer material RM82: photoinitiator Irg651: optical glue NOA65 = 90:2:0.2:7.8;

[0013] UV curing conditions: 50°C, 20mW / cm 2 Irradiate at a power density for half an hour to solidify and form a polymer network structure;

[0014] A transverse shear force is applied to the first alignment layer and the second alignment layer, so that the liquid crystal layer and the two alignment layers are dislocated and translated by a certain distance to form a stress polymer network liquid crystal layer.

[0015] Furthermore, the common electrode layer is a transparent conductive film layer.

[0016] Furthermore, the strip electrodes are strip electrodes made of transparent conductive films.

[0017] Furthermore, the two liquid crystal optical phased array device units are aligned in a horizontal position, and the strip electrodes in one liquid crystal optical phased array device unit are aligned one-to-one with the strip electrodes in the other liquid crystal optical phased array device unit.

[0018] Furthermore, for each liquid crystal optical phased array device unit, all of its strip electrodes are connected to the output pins of the on-chip driver chip, and the input pins of the on-chip driver chip are connected to the external drive circuit through the on-chip FPC cable.

[0019] Furthermore, the phase modulation of each liquid crystal optical phased array device unit is π, and a phase modulation amount of 2π is obtained by superimposing two liquid crystal optical phased array device units.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention adopts a two-layer liquid crystal optical phased array device unit device structure, and each liquid crystal optical phased array device unit device only needs to form a phase delay of π, which can also meet the phase delay requirement when the driving voltage reaches 40 to 60V;

[0022] (2) In order to cope with application scenarios with longer wavebands, the present invention can be further divided into a 4-layer structure, a 6-layer structure, or even higher. However, the more layers there are, the more complicated the actual assembly will be. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a fast-response liquid crystal optical phased array device proposed by the present invention;

[0024] Figure 2 is a schematic structural diagram of a first liquid crystal optical phased array device unit LCOPA1;

[0025] Figure 3 Schematic diagram of the structure of the second liquid crystal optical phased array device unit LCOPA2. DETAILED DESCRIPTION

[0026] The technical solution of this embodiment is now further described in conjunction with the accompanying drawings and embodiments.

[0027] like Figure 1As shown, this embodiment proposes a fast response liquid crystal optical phased array device, including at least two liquid crystal optical phased array device units stacked in sequence, from top to bottom, a first liquid crystal optical phased array device unit LCOPA1 and a second liquid crystal optical phased array device unit LCOPA2. The two liquid crystal optical phased array device units are bonded together by optical glue 12, and the first liquid crystal optical phased array device unit LCOPA1 and the second liquid crystal optical phased array device unit LCOPA2 are aligned in a horizontal position by aligning the first alignment mark 108 and the second alignment mark 208. The optical glue 12 mainly has two functions, one is mechanical connection, which bonds and fixes two adjacent liquid crystal optical phased array device units, and the other is optical anti-reflection effect. The refractive index of the optical glue is as equal as possible to the glass substrate of the two adjacent liquid crystal optical phased array device units to reduce the energy loss caused by Fresnel reflection of light.

[0028] Specifically, the first liquid crystal optical phased array device unit LCOPA1 and the second liquid crystal optical phased array device unit LCOPA2 are both sandwich structures.

[0029] The first liquid crystal optical phased array device unit LCOPA1 includes, from top to bottom, a first upper glass substrate layer 101, an upper common electrode layer 102, a first upper orientation layer 103, a first liquid crystal layer 104, a first lower orientation layer 105, a lower array electrode layer 106, and a first lower glass substrate layer 107. The first upper glass substrate layer 101 and the first lower glass substrate layer 107 are substrates of the first liquid crystal optical phased array device unit LCOPA1, and can be made of transparent materials such as optical glass, fused quartz glass, sapphire glass, etc. into a flat plate structure, polished on both sides, and having a thickness range of 0.1 to 5 mm.

[0030] The first upper alignment layer 103 and the first lower alignment layer 105 can use a rubbing alignment agent (including but not limited to polyimide film) or a photoalignment agent material (including but not limited to SD1 or brilliant yellow), and the alignment directions of the two are consistent, which is the X-axis direction; under the joint action of the two, the molecular director direction of the first liquid crystal layer 104 sandwiched therebetween is consistent with the alignment directions of the first upper alignment layer 103 and the first lower alignment layer 105, which is also the X-axis direction. Assuming that the angle between the liquid crystal alignment direction and the X-axis is θ, then θ=0°.

[0031] The lower array electrode layer 106 is composed of many periodic first strip electrodes to form a one-dimensional electrode array structure, and each first strip electrode is an array unit. Each first strip electrode is a transparent conductive film (including but not limited to ITO), which meets both the light transmission condition and the conductive condition, and is used to control the arrangement state of liquid crystal molecules in an array unit area. There is a micron-level spacing (such as 0.5-5um) between each first strip electrode, so that each adjacent first electrode unit is insulated, thereby realizing programmable independent control of the array electrode voltage. In the lower array electrode layer 106, the long side direction of each first strip electrode is parallel to the Y axis, and the short side direction is parallel to the X axis. The upper common electrode layer 102 is a layer of transparent conductive film (including but not limited to ITO), which meets both the light transmission condition and the conductive condition. It is used in pairs with the lower array electrode layer 106 to form a voltage difference, which is used to control the arrangement state of liquid crystal molecules in each array unit area.

[0032] The spatial positions of the functional layers of the first liquid crystal optical phased array device unit LCOPA1 are as follows: Figure 2 As shown. The lower array electrode layer 106 is located at the center of the first lower glass substrate layer 107. All the first strip electrodes A1, A2, ..., A M They are all connected to the output pins of the on-chip driver chip 109, where M is the number of channels for the multi-channel output voltage, such as M=240, 480, 960, or even more. The on-chip driver chip 109 can be 1, 2, or more, depending on the scale of the number of first strip electrodes. The input pins of the on-chip driver chip 109 are connected to the external drive circuit through the on-chip FPC cable. The first alignment marks 108 are distributed around the first lower glass substrate layer 107. Depending on the tightness of the spatial layout, the number of the first alignment marks 108 can be 1 to 4, or even more.

[0033] The second liquid crystal optical phased array device unit LCOPA2 is composed of a 7-layer sandwich structure. From top to bottom, they are the second upper glass substrate layer 207, the upper array electrode layer 206, the second upper orientation layer 205, the second liquid crystal layer 204, the second lower orientation layer 203, the lower common electrode layer 202, and the second lower glass substrate layer 201. The second upper glass substrate layer 207 and the second lower glass substrate layer 201 are used as substrates of the second liquid crystal optical phased array device unit LCOPA2. They can be made of transparent materials such as optical glass, fused quartz glass, sapphire glass, etc. into a flat plate structure, polished on both sides, and have a thickness range of 0.1 to 5 mm.

[0034] The upper array electrode layer 206 is composed of many periodic second strip electrodes to form a one-dimensional electrode array structure, and each second strip electrode is an array unit. The second electrode material is a transparent conductive film (including but not limited to ITO), which meets both the light transmission condition and the conductive condition, and is used to control the arrangement state of liquid crystal molecules in an array unit area. There is a micron-level spacing (such as 0.5 to 3um) between each second strip electrode, so that each adjacent second strip electrode is insulated, thereby realizing programmable independent control of the array electrode voltage. In the upper array electrode layer 206, the long side direction of each second strip electrode is parallel to the Y axis, and the short side direction is parallel to the X axis.

[0035] The second upper alignment layer 205 and the second lower alignment layer 203 may use a rubbing alignment agent (including but not limited to polyimide film) or a photoalignment agent material (including but not limited to SD1 or brilliant yellow), and their alignment directions are consistent, which is the X-axis direction; under the joint action of the two, the molecular director direction of the second liquid crystal layer 204 sandwiched therebetween is consistent with the alignment directions of the second upper alignment layer 205 and the second lower alignment layer 203, which is also the X-axis direction. Assuming that the angle between the liquid crystal alignment direction and the X-axis is θ, then θ=0°.

[0036] The lower common electrode layer 202 is a transparent conductive film (including but not limited to ITO) that satisfies both light transmission and conductivity requirements. It is used in pairs with the upper array electrode layer 206 to form a voltage difference to control the arrangement state of liquid crystal molecules in each array unit area.

[0037] The spatial positions of the functional layers of the second liquid crystal optical phased array device unit LCOPA2 are as follows: Figure 3 As shown. The upper array electrode layer 206 is located at the center of the second lower glass substrate layer 207, and all the second strip electrodes B1, B2, ..., B M They are all connected to the output pins of the on-chip driver chip 209, where M is the number of channels of the multi-channel output voltage, such as M=240, 480, 960, or even more. The on-chip driver chip 209 can be 1, 2, or more, depending on the scale of the number of second strip electrodes. The input pins of the on-chip driver chip 209 are connected to the external drive circuit through the on-chip FPC cable. The second alignment marks 208 are distributed around the second lower glass substrate layer 207. Depending on the tightness of the spatial layout, the number of second alignment marks 208 can be 1 to 4, or even more. By aligning the first alignment mark 108 and the second alignment mark 208, the first liquid crystal optical phased array device unit LCOPA1 and the second liquid crystal optical phased array device unit LCOPA2 are aligned in the horizontal position, especially the first strip electrode A1 and the second strip electrode B1 are aligned, A2 and B2 are aligned, and so on, until the last first strip electrode A M and the second strip electrode BM In this embodiment, the on-chip driver chip 109 is a high-voltage driver chip dedicated to liquid crystal, and the output voltage can reach 60V, or even 80V or higher.

[0038] The first liquid crystal layer 104 in the first liquid crystal optical phased array device unit LCOPA1 and the second liquid crystal layer 204 in the second liquid crystal optical phased array device unit LCOPA2 both adopt a structure of stress polymer liquid crystal material. Stress polymer liquid crystal material is a combination of materials and structures. Specifically, the stress polymer liquid crystal material is mixed with liquid crystal material, photosensitive polymer material, photoinitiator, optical glue and other materials, and is polymerized by ultraviolet light to form a composite material of liquid crystal and polymer network. The typical material ratio is: nematic liquid crystal material 5CB: photosensitive polymer material RM82: photoinitiator Irg651: optical glue NOA65 = 90:2:0.2:7.8, and the typical UV light curing conditions are 50°C, 20mW / cm 2 Irradiate at a power density of half an hour. Microscopically, in the composite material, the liquid crystal is divided into many small areas by the polymer network, also called liquid crystal domains. Macroscopically, the composite material is poured between two glass substrates (i.e., two orientation layers) to form a liquid crystal box before polymerization. After polymerization, a lateral misalignment displacement is applied to the upper and lower glass substrates, and the polymer network is straightened in a uniform direction, so that the liquid crystal domains between the polymer networks are uniformly oriented by stretching in a uniform direction. In order to achieve a better orientation effect, the direction of the lateral misalignment displacement in this embodiment is consistent with the orientation direction of the liquid crystal orientation layer. This lateral misalignment displacement is called the shear distance, and the typical distance is 80um.

[0039] The response time of stress polymer liquid crystal is very short, about ms or even shorter, and the response time is independent of the thickness of the liquid crystal box. This characteristic has high application value in mid-infrared, long-wave infrared and other bands. The disadvantage is that the driving voltage of stress polymer liquid crystal is relatively high, generally tens of volts or even hundreds of volts. It is OK when the number of driving paths is relatively small, but it cannot be realized when there are more paths.

[0040] For liquid crystal optical phased array devices, the number of electrode arrays is very large, and an on-chip integrated circuit structure must be adopted. However, the output voltage of conventional integrated circuits is limited, generally only reaching 40 to 60V. Liquid crystal phased array devices need to form at least a phase delay of 2π, and a driving voltage of 40 to 60V cannot meet the phase delay requirement. For this reason, this embodiment proposes a two-layer unit device structure. For a laser with a wavelength of λ=1.06um, the voltage to form a 2π phase delay is approximately 100V, and the corresponding voltage for half a wavelength and a π phase delay is 50V. In this way, each liquid crystal optical phased array device unit only needs to form a phase delay of π, so a driving voltage of 40 to 60V can basically meet the phase delay requirement.

Claims

1. A fast response liquid crystal optical phased array device, characterized in that: At least two liquid crystal optical phased array device units are included; Each liquid crystal optical phased array device unit has the same structure, and includes in sequence: a first glass substrate layer, a common electrode layer, a first orientation layer, a liquid crystal layer, a second orientation layer, an array electrode layer, and a second glass substrate layer; the first glass substrate layer and the second glass substrate layer serve as substrates of the liquid crystal optical phased array device unit; The first alignment layer and the second alignment layer have the same alignment direction, the liquid crystal layer is located between the first alignment layer and the second alignment layer, the liquid crystal layer is a stress polymer network liquid crystal layer, and the direction of its molecular director is consistent with the alignment direction of the first alignment layer; the array electrode layer is a one-dimensional electrode array structure composed of a plurality of strip electrodes, each strip electrode is an electrode array unit, the strip electrodes are insulated from each other, and the voltage of each strip electrode is independently controlled; The common electrode layer and the array electrode layer are used in pairs to form a voltage difference, which is used to control the arrangement state of liquid crystal molecules in each electrode array unit area.

2. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: The second glass substrate layer of one liquid crystal optical phased array device unit is bonded to the second glass substrate layer of another liquid crystal optical phased array device unit by optical glue, and the refractive index of the optical glue is consistent with the refractive index of the glass substrate layer of the liquid crystal optical phased array device unit.

3. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: The first alignment layer and the second alignment layer are rubbed alignment agent layers or photo-alignment agent layers.

4. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: The stress polymer network liquid crystal layer is prepared according to the following steps: Mix the materials in the following ratio: nematic liquid crystal material 5CB: photosensitive polymer material RM82: photoinitiator Irg651: optical glue NOA65 = 92:2:0.5:5.5; The UV light curing conditions are 60°C and 30mW / cm2 power density for half an hour to cure and form a polymer network structure; A transverse shear force is applied to the first alignment layer and the second alignment layer, so that the liquid crystal layer and the two alignment layers are dislocated and translated by a certain distance to form a stress polymer network liquid crystal layer.

5. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: The common electrode layer is a transparent conductive film layer.

6. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: The strip electrodes are strip electrodes made of transparent conductive films.

7. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: The two liquid crystal optical phased array device units are aligned in a horizontal position, and the strip electrodes in one liquid crystal optical phased array device unit are aligned one-to-one with the strip electrodes in another liquid crystal optical phased array device unit.

8. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: For each liquid crystal optical phased array device unit, all of its strip electrodes are connected to the output pins of the on-chip driver chip, and the input pins of the on-chip driver chip are connected to the external drive circuit through the on-chip FPC cable.

9. The fast response liquid crystal optical phased array device according to claim 1, characterized in that: The phase modulation of each liquid crystal optical phased array device unit is π, and a phase modulation amount of 2π is obtained by superimposing two liquid crystal optical phased array device units.

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