Liquid crystal wave plate made of micro-channel substrate

Abstract

The invention discloses a liquid crystal wave plate made of a micro-channel substrate. The liquid crystal wave plate is composed of a first antireflection film layer, a first micro-channel substrate, a first ITO electrode layer, a first polyimide orientation layer, a liquid crystal layer, a second polyimide orientation layer, a second ITO electrode layer, a second micro-channel substrate and a second antireflection film layer. A glass substrate is machined to obtain a major arc-shaped rectangular groove and two linear rectangular grooves which are parallel to each other and are horizontally symmetrical at the two ends of the major arc-shaped rectangular groove, the two glass grooves are completely attached to each other and then are subjected to high-temperature and high-pressure bonding to obtain a micro-channel substrate, an antireflection film is plated on one side of a water inlet and a water outlet, and an ITO film is plated on the other side of the water inlet and the water outlet. According to the invention, the micro-channel through which a large-caliber light spot can pass is manufactured on the liquid crystal wave plate, and the water cooling machine supplies water and flows in the micro-channel, so that the temperature rise of the device caused by laser irradiation is reduced under the condition that large-caliber incident light is not influenced, and the device reliability is improved. And the liquid crystal wave plate can still work normally under high power density under the irradiation of large-aperture light spots.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal optical field control technology, and specifically relates to a liquid crystal waveplate made of a microchannel substrate under the working conditions of large-aperture high-power continuous laser. Background Technology

[0002] Liquid crystal waveplates possess phase modulation capabilities and have wide applications in coherent wavefront correction and beam deflection. Under large-aperture, high-power continuous laser irradiation, the device generates significant thermal effects, leading to temperature increases and a Gaussian envelope gradient temperature distribution. This results in a degradation of the device's phase modulation characteristics. Therefore, maintaining the phase modulation characteristics of liquid crystal waveplates under large-aperture, high-power continuous laser operating conditions is crucial. Previous research has mainly focused on reducing the absorption of the transparent conductive layer, increasing auxiliary heat dissipation, and using a substrate with a higher thermal diffusivity. Among the research on increasing auxiliary heat dissipation, the University of Electronic Science and Technology of China fabricated a transmissive liquid crystal optical phased array with a rear heat sink. The rear heat sink has microchannels etched inside, and a liquid with a refractive index matching the substrate is selected as the heat dissipation liquid. The heat dissipation liquid is flowed at an appropriate flow rate to remove heat from the device. However, finding a liquid with a refractive index matching the glass substrate is quite difficult. Moreover, when light passes through the heat dissipation liquid and the microchannels, the transmitted light is still affected by scattering and other factors, which is especially noticeable when a large aperture light spot is incident. This makes it unusable under large aperture light spots. Furthermore, because it is a straight microchannel, the heat dissipation liquid enters on one side and flows out on the other side, resulting in uneven heat dissipation of the entire device. The side where the heat dissipation liquid enters is more effective, while the side closer to the outflow is less effective, resulting in uneven temperature distribution on the device. The overall temperature distribution shifts with the direction of water flow, which is also unfavorable for its application under large aperture light spot irradiation conditions. The microchannels described in this invention are fabricated inside the substrate, simplifying the device structure and providing a large aperture for light to pass through. Incident light does not pass through the heat dissipation liquid or the microchannels, thus not affecting the transmitted beam. Furthermore, experimental verification shows that the temperature distribution on the device does not shift with the flow direction of the heat dissipation liquid after heat dissipation, resulting in a more uniform temperature distribution across the entire device. Therefore, this invention proposes a microchannel heat dissipation system integrated with the device that does not affect the transmitted beam and enables a more uniform temperature distribution, applicable to liquid crystal waveplates in large-aperture light spot systems. Summary of the Invention

[0003] Current liquid crystal waveplates experience significant temperature rise under continuous laser irradiation with large aperture spots, leading to uneven temperature distribution and a large temperature gradient between the device edge and the irradiation center. These problems limit the application of liquid crystal waveplates in large-aperture, high-power continuous laser systems. This invention proposes a microchannel liquid crystal waveplate with a microchannel heat dissipation system integrated into the substrate without affecting the transmission of large-aperture beams. The microchannel liquid crystal waveplate consists of two microchannel substrates, with a ring-shaped front view. The area enclosed by the ring channel is the light-transmitting aperture. The inlet and outlet are connected to the ring channel via direct current channels. The water flow directions of the two microchannel substrates are opposite to ensure more balanced heat dissipation. This device can be applied to large-aperture continuous laser systems because the ring-shaped microchannel effectively removes the heat generated by continuous laser irradiation, resulting in a more uniform temperature distribution on the device and a smaller temperature gradient between the device edge and the irradiation center. This effectively maintains the phase modulation characteristics and phase uniformity of the liquid crystal waveplate.

[0004] The technical solution of the present invention is as follows:

[0005] A liquid crystal waveplate fabricated from a microchannel substrate is used in a large-aperture, high-power continuous laser system, achieved through the following technical solution:

[0006] The liquid crystal waveplate comprises, from top to bottom, a first antireflection film layer, a first microchannel substrate, a first ITO electrode layer, a first PI alignment film, a liquid crystal layer encapsulated by spacers, a second PI alignment film, a second ITO electrode layer, a second microchannel substrate, and a second antireflection film layer.

[0007] The first microchannel substrate has a first microchannel inside. The first microchannel is composed of a first arc-shaped rectangular tube and two parallel and horizontally symmetrical linear rectangular tubes connected to each other. Two holes are formed on the upper side of the first microchannel substrate as a first water inlet and a first water outlet, which are respectively connected to the two ports of the first and second linear rectangular tubes.

[0008] The second microchannel substrate has a second microchannel inside. The second microchannel is composed of a second arc-shaped rectangular tube and a third and fourth linear rectangular tubes that are parallel to each other and horizontally symmetrical at both ends of the second arc-shaped rectangular tube. Two holes are formed on the lower side of the second microchannel substrate as a second water inlet and a second water outlet, which are respectively connected to the two ports of the third and fourth linear rectangular tubes.

[0009] The first and second microchannels are identical in shape and size and are symmetrically rotated 180° from the center. That is, the first and second linear rectangular tubes, the third and fourth linear rectangular tubes are located on both sides of the first and second arc-shaped rectangular tubes, respectively, and the water flow direction in the first and second arc-shaped rectangular tubes is the same.

[0010] Furthermore, PEEK bases are fixed at the first inlet and the first outlet, as well as at the second inlet and the second outlet, respectively, for connecting PFA pipes to enable the flow of cooling water.

[0011] Furthermore, the thickness of the first microchannel substrate and the second microchannel substrate is 5mm to 5.5mm, the width of the first microchannel and the second microchannel is 1.5mm to 2mm, and the height is less than the height of the first microchannel substrate and the second microchannel substrate. The inner diameter of the first and second arc-shaped rectangular tubes is 10mm to 15mm, the diameter of the PEEK base is not less than 10mm, the distance between the first and second linear rectangular tubes and the distance between the third and fourth linear rectangular tubes are not less than the diameter of the PEEK base, and the length of the first and second linear rectangular tubes and the third and fourth linear rectangular tubes is greater than the radius of the PEEK base.

[0012] Preferably, the thickness of the first microchannel substrate and the second microchannel substrate is 5.5 mm, the width of the first microchannel and the second microchannel is 1.5 mm, the height is 2 mm, the inner diameter of the first and second arc-shaped rectangular tubes is 15 mm, and the diameter of the PEEK base is 10 mm.

[0013] Furthermore, the diameter of the incident light spot is smaller than the inner diameter of the first and second arc-shaped rectangular tubes.

[0014] Furthermore, the PEEK base maintains a certain distance from the first and second curved rectangular tubes.

[0015] This invention also includes a method for fabricating a liquid crystal waveplate made from a microchannel substrate:

[0016] S1: Two arc-shaped rectangular grooves are formed on the surfaces of two glass pieces by mechanical processing and HF wet etching, and two parallel and horizontally symmetrical linear rectangular grooves are set at both ends of each arc-shaped rectangular groove. The two arc-shaped rectangular grooves and four linear rectangular grooves of the two glass pieces are attached to each other, and the two glass pieces are bonded by high temperature and high pressure to form a first microchannel substrate and a first arc-shaped rectangular tube and a first and second linear rectangular tube that are interconnected inside. Two holes are drilled on the upper side of the first microchannel substrate as a first water inlet and a first water outlet, which are respectively connected to the two ports of the first and second linear rectangular tubes.

[0017] S2: Two arc-shaped rectangular grooves are formed on the surfaces of two other glass pieces by mechanical processing and HF wet etching, and two parallel and horizontally symmetrical linear rectangular grooves are set at both ends of each arc-shaped rectangular groove. The two arc-shaped rectangular grooves and four linear rectangular grooves of the two glass pieces are attached to each other, and the two glass pieces are bonded by high temperature and high pressure to form a second microchannel substrate and a second arc-shaped rectangular tube and a third and fourth linear rectangular tube that are interconnected inside. Two holes are drilled on the lower side of the second microchannel substrate as a second water inlet and a second water outlet, which are respectively connected to the two ports of the third and fourth linear rectangular tubes.

[0018] S3: Perform chemical mechanical polishing on the surfaces of the first microchannel substrate and the second microchannel substrate;

[0019] S4: Deposit a first antireflection film layer and a second antireflection film layer on one side of the first inlet and first outlet of the first microchannel substrate, and a second inlet and a second outlet of the second microchannel substrate, respectively; deposit a first ITO electrode layer and a second ITO electrode layer on the other side, and then clean.

[0020] S5: Spin-coating and rubbing alignment of the first PI alignment film and the second PI alignment film are performed respectively, followed by dispensing, pressing, crystal filling, and encapsulation to finally obtain the microchannel liquid crystal waveplate.

[0021] Use UV-curing adhesive to fix the PEEK base to the first inlet and first outlet, and the second inlet and second outlet of the microchannel liquid crystal waveplate. The water chiller is connected to the microchannel liquid crystal waveplate through PFA tubes and the PEEK base. Turn on the water chiller to complete water circulation. As long as there is no leakage, it is fine.

[0022] The first inlet and the first outlet, the second inlet and the second outlet are used for the inflow and outflow of heat dissipation liquid, respectively. The heat dissipation liquid flows in from the first inlet and the second inlet at the same time, flows through the entire first microchannel and the second microchannel, carries away the heat deposited on the device, and flows out from the first outlet and the second outlet.

[0023] The beneficial effects of this invention are as follows: The microchannel liquid crystal waveplate of this invention integrates the heat dissipation microchannel with the device system into one unit. The microchannel uses an arc-shaped rectangular tube connected to a linear rectangular tube, leaving a light-transmitting aperture that allows a large-diameter light spot to pass through. It does not require a coolant with a refractive index matching the substrate, thus eliminating concerns about affecting the transmitted light. Experimental verification shows that it can also effectively remove heat from the device, allowing the phase modulation characteristics of the liquid crystal waveplate to be well maintained within the light-transmitting aperture range, and effectively improving the phase modulation uniformity within the light-transmitting aperture range, thereby effectively increasing the laser power that the liquid crystal waveplate can withstand. Attached Figure Description

[0024] Figure 1This is a schematic diagram of the structure of the liquid crystal waveplate fabricated from the microchannel substrate of the present invention;

[0025] Figure 2 This is a schematic diagram of the microchannels in the first microchannel substrate of the present invention;

[0026] Figure 3 This is a schematic diagram of the microchannels in the second microchannel substrate of the present invention;

[0027] Figure 4 This is a three-dimensional schematic diagram of the liquid crystal waveplate of the present invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1-First antireflection film layer, 2-First microchannel substrate, 3-First ITO electrode layer, 4-First PI alignment film, 5-Liquid crystal layer, 6-Second PI alignment film, 7-Second ITO electrode layer, 8-Second microchannel substrate, 9-Second antireflection film layer, 10-Spacer, 11-PEEK base, 21-First microchannel, 211-First arc-shaped rectangular tube, 212-First linear rectangular tube, 212'-Second linear rectangular tube, 213-First inlet, 213'-First outlet, 81-Second microchannel, 811-Second arc-shaped rectangular tube, 812-Third linear rectangular tube, 812'-Fourth linear rectangular tube, 813-Second inlet, 813'-Second outlet Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] like Figure 1 The microchannel liquid crystal waveplate shown includes, from top to bottom, a first antireflection film layer, a first microchannel substrate, a first ITO electrode layer, a first PI alignment film, a liquid crystal layer encapsulated by spacers, a second PI alignment film, a second ITO electrode layer, a second microchannel substrate, and a second antireflection film layer.

[0032] The first microchannel substrate contains a first microchannel, which is formed by a first arc-shaped rectangular tube and two parallel and horizontally symmetrical linear rectangular tubes connected at both ends of the first arc-shaped rectangular tube. Two holes are formed on the upper side of the first microchannel substrate as a first inlet and a first outlet, respectively connecting to the two ends of the first and second linear rectangular tubes. The second microchannel substrate contains a second microchannel, which is formed by a second arc-shaped rectangular tube and two parallel and horizontally symmetrical linear rectangular tubes connected at both ends of the second arc-shaped rectangular tube. Two holes are formed on the lower side of the second microchannel substrate as a second inlet and a second outlet, respectively connecting to the two ends of the third and fourth linear rectangular tubes. The first and second linear rectangular tubes and the third and fourth linear rectangular tubes are located on both sides of the first and second arc-shaped rectangular tubes, respectively, and the water flow direction in the first and second arc-shaped rectangular tubes is the same.

[0033] The thickness of the first microchannel substrate and the second microchannel substrate is 5.5 mm, the width of the first microchannel and the second microchannel is 1.5 mm, the height is 2 mm, the inner diameter of the first and second arc-shaped rectangular tubes is 15 mm, and the diameter of the PEEK base is 10 mm.

[0034] like Figure 3 The specific fabrication method of the microchannel liquid crystal waveplate shown is as follows:

[0035] S1. Two arc-shaped rectangular grooves are formed on the surfaces of two 2.75mm thick glass pieces by mechanical processing and HF wet etching, and two parallel and horizontally symmetrical linear rectangular grooves are set at both ends of each arc-shaped rectangular groove. The two arc-shaped rectangular grooves and four linear rectangular grooves of the two glass pieces are attached to each other, and the two glass pieces are bonded together by high temperature and high pressure to form a first microchannel substrate and a first arc-shaped rectangular tube and a first and second linear rectangular tube that are interconnected inside. Two holes are drilled on the upper side of the first microchannel substrate as a first water inlet and a first water outlet, which are respectively connected to the two ports of the first and second linear rectangular tubes.

[0036] S2. Two arc-shaped rectangular grooves and two parallel and horizontally symmetrical linear rectangular grooves are formed on the surfaces of two other glass pieces by mechanical processing and HF wet etching, respectively. The two arc-shaped rectangular grooves and four linear rectangular grooves of the two glass pieces are attached to each other, and the two glass pieces are bonded together by high temperature and high pressure to form a second microchannel substrate and a second arc-shaped rectangular tube and a third and fourth linear rectangular tube that are interconnected inside. Two holes are drilled on the lower side of the second microchannel substrate as a second water inlet and a second water outlet, which are respectively connected to the two ports of the third and fourth linear rectangular tubes.

[0037] S3. After the microchannel substrate is bonded, the surface will be somewhat rough due to the high pressure during the bonding process. Chemical mechanical polishing is then performed on it.

[0038] S4. A first antireflection film layer and a second antireflection film layer are deposited on one side of the first inlet and first outlet of the first microchannel substrate, and on the other side of the second inlet and second outlet of the second microchannel substrate, respectively. Then, a first ITO electrode layer and a second ITO electrode layer are deposited on the other side, and then the substrate is cleaned.

[0039] S5. Spin-coating and rubbing alignment of the first PI alignment film and the second PI alignment film are performed respectively, followed by dispensing, pressing, crystal filling, and encapsulation to finally obtain the microchannel liquid crystal waveplate.

[0040] The PEEK base is fixed to the first inlet and first outlet, the second inlet and the second outlet of the microchannel liquid crystal waveplate using UV-curing adhesive, and then PFA tubes are connected to achieve the flow of cooling water.

[0041] The first and second microchannels are 1.5 mm wide and 2 mm high. The inner diameter of the first and second arc-shaped rectangular tubes is 15 mm. The area where the heat dissipation liquid flows is outside a circle with a radius of 7.5 mm centered on the substrate center. The flow rate can be controlled by changing the flow rate of the heat dissipation liquid.

[0042] Furthermore, the flow direction of the heat dissipation liquid in both the first and second microchannel substrates is clockwise, which ensures uniform heat dissipation. Specifically, the positions of the inlet and outlet are as follows: Figure 3 Note: The area enclosed by the annular microchannels is the aperture of the incident light, a circle with a diameter of 15mm. Therefore, as long as the diameter of the incident light spot is less than 15mm, it is no different from incident light on a regular liquid crystal waveplate and will not affect the incident light. The PEek base, which connects the microchannel tubes, has a diameter of 10mm and is located on the far left of the substrate, away from the aperture area, making it possible for the liquid crystal waveplate to be used in large-aperture, high-power continuous laser systems.

[0043] like Figure 1 and Figure 2As shown, the microchannel liquid crystal waveplate of the present invention does not require alteration of the original liquid crystal waveplate structure. Instead, the annular microchannel is directly integrated with the substrate of the liquid crystal waveplate, improving the device's tolerance to large-aperture, high-power lasers compared to the original liquid crystal waveplate. For liquid crystal waveplates, the primary problem during large-aperture, high-power laser incidence is the absorption of laser light by various film layers, leading to an increase in the overall device temperature. When the temperature rises to the phase transition temperature of the liquid crystal material, also known as the clearing point, the liquid crystal undergoes a phase transition, changing from anisotropic to isotropic, losing its phase modulation characteristics. Therefore, the purpose of this invention is to reduce the temperature rise of the entire device during high-power laser incidence. This invention addresses the phenomenon that as the temperature rises, a temperature gradient appears throughout the device, exhibiting a high temperature at the center and decreasing temperature towards the outer edges. This leads to a significant difference in phase modulation between the center and outer regions of the liquid crystal waveplate. Consequently, the phase modulation effect of the liquid crystal waveplate on the incident light is greatly degraded or even rendered unusable under continuous laser irradiation with a large aperture spot. To solve this problem, an annular microchannel is designed while maintaining the light transmission aperture under large aperture irradiation. This effectively reduces the temperature gradient on the device surface without affecting the incident light under high-power continuous laser irradiation with a large aperture spot, allowing the phase modulation characteristics of the device to maintain a small difference over a larger range. This enables its application in laser systems with a large spot size.

[0044] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A liquid crystal waveplate fabricated from a microchannel substrate, characterized in that, The liquid crystal waveplate comprises, from top to bottom, a first antireflection film layer (1), a first microchannel substrate (2), a first ITO electrode layer (3), a first PI alignment layer (4), a liquid crystal layer (5) encapsulated by spacers (10), a second PI alignment thin film layer (6), a second ITO electrode layer (7), a second microchannel substrate (8), and a second antireflection film layer (9). The first microchannel substrate (2) has a first microchannel (21) inside. The first microchannel (21) is formed by connecting a first arc-shaped rectangular tube (211) and two parallel and horizontally symmetrical linear rectangular tubes (212, 212') at both ends of the first arc-shaped rectangular tube. Two holes are formed on the upper side of the first microchannel substrate (2) as a first inlet (213) and a first outlet (213') to connect to the two ports of the first and second linear rectangular tubes (212, 212') respectively. The second microchannel substrate (8) is provided with a second microchannel (81) inside. The second microchannel (81) is composed of a second arc-shaped rectangular tube (811) and a third and fourth linear rectangular tube (812, 812') that are parallel to each other and horizontally symmetrical at both ends of the second arc-shaped rectangular tube. Two holes are formed on the lower side of the second microchannel substrate (8) as a second inlet (813) and a second outlet (813') to connect to the two ports of the third and fourth linear rectangular tubes (812, 812') respectively. After the first microchannel (21) is rotated 180° along the center, it is symmetrical with the second microchannel (81) vertically. The water flow direction in the first arc-shaped rectangular tube (211) and the second arc-shaped rectangular tube (811) is the same.

2. The liquid crystal waveplate fabricated from a microchannel substrate as described in claim 1, characterized in that, PEEK bases (11) are fixed at the first inlet (213) and the first outlet (213'), the second inlet (813) and the second outlet (813') respectively to connect PFA (soluble polytetrachloroethylene) pipes to achieve the flow of cooling water.

3. A liquid crystal waveplate fabricated from a microchannel substrate as described in claim 2, characterized in that, The thickness of the first microchannel substrate (2) and the second microchannel substrate (8) is 5mm to 5.5mm, the width of the first microchannel (21) and the second microchannel (81) is 1.5mm to 2mm, and the height is less than the thickness of the first microchannel substrate (2) and the second microchannel substrate (8). The inner diameter of the first arc-shaped rectangular tube (211) and the second arc-shaped rectangular tube (811) is 10mm to 15mm. The diameter of the PEEK base (11) is not less than 10mm. The distance between the first and second linear rectangular tubes (212, 212') and the distance between the third and fourth linear rectangular tubes (812, 812') are not less than the diameter of the PEEK base (11). The length of the first and second linear rectangular tubes (212, 212') and the third and fourth linear rectangular tubes (812, 812') is greater than the radius of the PEEK base (11).

4. A liquid crystal waveplate fabricated from a microchannel substrate as described in claim 3, characterized in that, The thickness of the first microchannel substrate (2) and the second microchannel substrate (8) is 5.5 mm, the width of the first microchannel (21) and the second microchannel (81) is 1.5 mm, the height is 2 mm, the inner diameter of the first arc-shaped rectangular tube (211) and the second arc-shaped rectangular tube (811) is 15 mm, and the diameter of the PEEK base (11) is 10 mm.

5. A liquid crystal waveplate fabricated from a microchannel substrate as described in claim 1, characterized in that, The diameter of the incident light spot is smaller than the inner diameter of the first and second arc-shaped rectangular tubes (211 and 811).

6. A liquid crystal waveplate fabricated from a microchannel substrate as described in claim 2, characterized in that, The PEEK base (11) maintains a certain distance from the first and second curved rectangular tubes (211 and 811).

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