Liquid crystal polarization controller

Abstract

The utility model relates to the field of classical optical communication and quantum communication, specifically disclose a liquid crystal polarization controller, including liquid crystal box (302), tube shell cover board (305) and butterfly tube shell (303), liquid crystal box (302) is fixed in butterfly tube shell (303), and tube shell cover board (305) covers on butterfly tube shell (303). The utility model has the advantages of: adaptability and easy integrability: liquid crystal polarization controller adopts standard butterfly package structure, carries out high density integration to liquid crystal box, realizes the significant reduction of device volume.

Description

Technical Field

[0001] This application relates to the fields of classical optical communication and quantum communication, and in particular to a liquid crystal polarization controller. Background Technology

[0002] Polarization state is a fundamental physical property of light and, as an important degree of freedom for information, is widely used in classical optical communication, quantum key distribution, and precision measurement. These applications often require precise control of the polarization state, while placing higher demands on device miniaturization, performance improvement, and reliability. Therefore, developing polarization control devices with higher integration, smaller size, and more stable and reliable performance is of great significance.

[0003] Based on differences in materials, structure, and principles, electrically controlled polarization controllers are mainly classified into waveplate type, extrusion type, electro-optic crystal type, and liquid crystal type. Waveplate type polarization controllers employ a series structure of λ / 4, λ / 2, and λ / 4 waveplates, utilizing the birefringence effect of the waveplates to control the polarization state. However, they typically require mounting the waveplates on a rotary stepper motor to achieve electromechanical rotation, resulting in a large overall structure. Extrusion type polarization controllers are based on the photoelastic effect, using piezoelectric ceramics to extrude optical fibers to introduce birefringence and dynamically control the polarization state. However, this method requires a special mechanical structure to apply pressure to the cylindrical optical fiber, also resulting in a large size. Furthermore, stress is generated during the extrusion process, leading to creep phenomena that gradually degrade polarization modulation performance. Electro-optic crystal type polarization controllers utilize the electro-optic effect of crystals, changing the refractive index of the integrated optical waveguide through an applied voltage to achieve modulation. However, due to the absorption of light waves by the material itself, insertion loss is high, and the modulation effect also exhibits creep over long-term operation, affecting stability. Liquid crystal polarization controllers typically employ a 3- or 4-cell series structure. Based on voltage-controlled liquid crystal molecule alignment, they achieve precise control of polarization state by altering the birefringence characteristics resulting from anisotropy. This technology fundamentally avoids polarization creep.

[0004] While the aforementioned liquid crystal polarization controller does not exhibit polarization creep, it suffers from varying degrees of technical limitations compared to other types of polarization controllers. These limitations are detailed below: 1) The current packaging structure of liquid crystal polarization devices has poor adaptability, which restricts the application of the devices in integration and the packaging size is large.

[0005] 2) The large package size of liquid crystal polarization devices is mainly due to the large package size of the core component inside the polarization controller: the liquid crystal cell. When attempting to reduce the size of the liquid crystal cell, the packaging process faces challenges. The liquid crystal cell is prone to liquid crystal leakage in high-temperature environments, which affects the polarization modulation performance. On the other hand, the overall size is limited by the integration of the entire device.

[0006] 3) The device has high insertion loss. Utility Model Content

[0007] The technical problem to be solved by this utility model is how to improve the compatibility of the packaging structure of the liquid crystal polarization controller.

[0008] The present invention solves the above-mentioned technical problems through the following technical means: a liquid crystal polarization controller, including a liquid crystal cell (302), a tube cover plate (305) and a butterfly tube shell (303), wherein the liquid crystal cell (302) is fixed inside the butterfly tube shell (303) and the tube cover plate (305) covers the butterfly tube shell (303).

[0009] As a further optimized technical solution, the liquid crystal polarization controller also includes a ceramic substrate (304), a semiconductor cooler (306), a thermistor (307), and a light transmission device. Multiple liquid crystal cells (302) are arranged to form a liquid crystal cell array and fixed on the ceramic substrate (304). The ceramic substrate (304) is fixed on the upper surface of the semiconductor cooler (306). The thermistor (307) is fixed on the upper surface of the ceramic substrate (304). The thermistor (307) is connected to the corresponding pin of the butterfly shell (303) by gold wire bonding. The light transmission device is fixed on the left and right sides of the butterfly shell (303).

[0010] As a further optimized technical solution, the liquid crystal polarization controller also includes a metal pad (301), with a metal pad (301) fixed to the bottom of each liquid crystal cell (302), and the metal pad (301) is fixed on the ceramic substrate (304).

[0011] As a further optimized technical solution, the optical transmission device is an optical fiber collimator (308) or an optical window (401).

[0012] As a further optimized technical solution, the liquid crystal cell includes a first substrate (101), a second substrate (102), a spacer (103), an electrode (104), a frame (105), an ITO film (106), and an alignment layer (107). The inner sides of the first substrate (101) and the second substrate (102) are respectively coated with an ITO film (106) and an alignment layer (107) in parallel and opposite directions. The electrode (104) is located at the lower part of the liquid crystal cell. The spacer (103) and the frame (105) are disposed between the first substrate (101) and the second substrate (102). The frame (105) seals the cell thickness supported by the spacer (103) and leaves a liquid crystal filling port (109).

[0013] As a further optimized technical solution, antireflective coatings (108) are deposited on the outer sides of the first substrate (101) and the second substrate (102).

[0014] As a further optimized technical solution, the plastic frames (105) on both sides of the liquid crystal inlet (109) are provided with upward protrusions (110), the top of which is in close contact with the upper edge of the liquid crystal cell.

[0015] As a further optimized technical solution, the second substrate (102) is longer than the first substrate (101), the first substrate (101) and the second substrate (102) are parallel and have one end flush, the other end of the second substrate (102) protrudes from the first substrate (101), and the electrode (104) is located outside the part of the second substrate (102) that protrudes from the first substrate (101).

[0016] As a further optimized technical solution, a metal pad (301) is fixed to the bottom of each liquid crystal cell (302). The metal pad (301) is fixed on the ceramic substrate (304). The metal pad (301) includes a base (3011) and a support back (3012) located outside the base (3011). The bottom surface of the second substrate (102) protruding from the first substrate (101) is bonded to the upper surface of the base (3011), and the side surface of the second substrate (102) protruding from the first substrate (101) is bonded to the inner side surface of the support back (3012).

[0017] As a further optimized technical solution, the inner side of the support backrest (3012) is recessed at the position where it contacts the upper surface of the base (3011) to form a groove, and the groove extends through the support backrest (3012) from front to back.

[0018] The advantages of this utility model are: 1) Adaptability and ease of integration: The liquid crystal polarization controller adopts a standard butterfly packaging structure to integrate the liquid crystal cell at high density, which significantly reduces the size of the device. It can modulate the polarization state of both free space light and light in optical fiber, which significantly improves the device's versatility, ease of integration and convenience of engineering applications.

[0019] 2) Higher reliability: The design of the liquid crystal cell frame structure improves the reliability of the packaging.

[0020] 3) Low insertion loss: Anti-reflection coatings are deposited on both the incident interface of the first substrate and the exit interface of the second substrate of the liquid crystal cell to effectively suppress light reflection and reduce device insertion loss. Attached Figure Description

[0021] Figure 1 This is an exploded view of the liquid crystal polarization controller according to an embodiment of this utility model; Figure 2 This is a schematic diagram of a fiber optic polarization state modulation liquid crystal polarization controller according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a free-space optical polarization state modulation liquid crystal polarization controller according to an embodiment of this utility model; Figure 4 This is a schematic diagram of the left side of the empty liquid crystal cell according to an embodiment of this utility model; Figure 5 This is a schematic diagram of the main view of the liquid crystal empty cell according to an embodiment of this utility model; Figure 6 This is a left-side view of the liquid crystal cell with the spacer portion omitted in this embodiment of the utility model; Figure 7 This is a front view schematic diagram of the liquid crystal cell of this utility model embodiment, omitting all spacers; Figure 8 This is a schematic diagram of the liquid crystal cell assembly according to an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0023] See Figures 1 to 3 The liquid crystal polarization controller provided in this embodiment adopts a highly integrated butterfly-shaped packaging scheme. This butterfly-shaped packaging scheme allows the liquid crystal polarization controller to be configured as follows: Figure 1 , 2 The free space light shown is as follows Figure 3 The two polarization modulation modes of optical fiber are shown.

[0024] Among them, fiber polarization state modulation schemes such as Figure 1 As shown, the liquid crystal polarization controller employing a fiber optic polarization state modulation scheme includes components such as a metal pad 301, a liquid crystal cell 302, a butterfly-shaped tube shell 303, a ceramic substrate 304, a tube shell cover 305, a semiconductor cooler 306, a thermistor 307, and a fiber optic collimator 308. Multiple liquid crystal cells 302 are arranged to form a liquid crystal cell array. A metal pad 301 is fixed to the bottom of each liquid crystal cell 302. The metal pad 301 is fixed to the ceramic substrate 304, which is fixed to the upper surface of the semiconductor cooler 306. The thermistor 307 is fixed to the upper surface of the ceramic substrate 304 and is connected to the corresponding pin of the butterfly-shaped tube shell 303 via gold wire bonding. The fiber optic collimator 308 is fixed to the left and right sides of the butterfly-shaped tube shell 303, and the tube shell cover 305 covers the butterfly-shaped tube shell 303.

[0025] The liquid crystal cell 302 is formed by filling a liquid crystal cell with liquid crystal and then sealing it. The liquid crystal cell of this embodiment of the present invention is as follows: Figure 4 and Figure 5 As shown, the liquid crystal cell includes a first substrate 101, a second substrate 102, spacers 103, electrodes 104, and a frame 105. An ITO film 106 and an alignment layer 107 are sequentially deposited on the inner sides of the first substrate 101 and the second substrate 102, respectively. The ITO film 106 is used for conductivity, and the alignment layer 107 is used to induce and anchor the alignment direction of liquid crystal molecules. By rubbing different alignment directions on the alignment layer 107, liquid crystal molecules can be aligned in different directions. The outer sides of the first substrate 101 and the second substrate 102 serve as optical interfaces, and antireflection films 108 are deposited on them to effectively suppress light reflection and reduce device insertion loss.

[0026] The first substrate 101 and the second substrate 102 are transparent substrates, generally made of glass. The second substrate 102 is longer than the first substrate 101. The first substrate 101 and the second substrate 102 are parallel and have one end flush with each other. The other end of the second substrate 102 protrudes from the first substrate 101.

[0027] Spacer 103 is located between the first substrate 101 and the second substrate 102 and is used to support the thickness of the box. Spacer 103 is a microsphere spacer, such as silica microsphere spacer, polystyrene microsphere spacer, or core-shell microsphere spacer, etc.

[0028] Electrode 104 is located at the lower part of the liquid crystal cell and is used to connect the driving signal. Specifically, electrode 104 is located on the outer side of the portion of the second substrate 102 that protrudes from the first substrate 101.

[0029] The frame 105 is used to seal the cell thickness supporting the spacer 103 from all sides. A liquid crystal filling port 109 is provided on one side of the frame 105 that is flush with the first substrate 101 and the second substrate 102. The thickness of the frame 105 must be greater than or equal to the diameter of the spacer 103. The frame 105 can be made of epoxy resin, AB adhesive, etc. The frame 105 on both sides of the liquid crystal filling port 109 has upward-facing protrusions 110. The top of these protrusions 110 is in close contact with the upper edge of the liquid crystal cell, thus forming an effective seal for the liquid crystal after encapsulation. This structural design prevents liquid crystal leakage, ensures stable polarization modulation performance, and avoids damage to the liquid crystal cell during the dicing process. In this application, the frame 105 formed by mixing the adhesive and the spacer 103 is disposed around the periphery of the opposing surfaces of the first substrate 101 and the second substrate 102.

[0030] Combination Figure 6 and Figure 7 As shown, where Figure 6Part of the spacer 103 is omitted to allow the injected liquid crystal 201 to be displayed. The preparation method of the liquid crystal cell of this utility model is as follows: S1. ITO films 106 are deposited on the inner sides of the first substrate 101 and the second substrate 102 respectively. An alignment layer 107 is deposited on the surface of the ITO films 106 on the first substrate 101 and the second substrate 102. An antireflection film 108 is deposited on the outer sides of the first substrate 101 and the second substrate 102 respectively. The processes of depositing ITO films 106, depositing alignment layers 107 and depositing antireflection films 108 can all adopt conventional processes. S2. Place the spacer 103 into the glue and stir evenly to form a mixture of spacer 103 and glue; S3. Apply the mixture of spacer 103 and adhesive to the periphery of the opposite surfaces of the first substrate 101 and the second substrate 102, and press the first substrate 101 and the second substrate 102 together. Leave a liquid crystal filling port 109 at one end of the first substrate 101 and the second substrate 102 that is flush with it, and form an upward protrusion structure 110 on both sides of the liquid crystal filling port 109. The mixture can be applied only to the first substrate 101 or the second substrate 102, or it can be applied to the corresponding positions of the first substrate 101 and the second substrate 102. S4. The first substrate 101 and the second substrate 102 coated with the mixture are cured at high temperature. After the glue is cured, a frame 105 is formed. The frame 105 and the first substrate 101 and the second substrate 102 form a liquid crystal filling space to form a liquid crystal cell. S5. Vacuum the liquid crystal filling space of the empty liquid crystal cell. S6. Then, liquid crystal 201 is dripped into the liquid crystal inlet 109. Using the pressure difference between the inside and outside of the cell, liquid crystal 201 is drawn in and fills the entire liquid crystal filling space. S7. Next, the empty liquid crystal cell filled with liquid crystal 201 is placed on a cooling platform for low-temperature treatment, so that the liquid crystal 201 actively shrinks. S8. Then, a sealing operation is performed at the liquid crystal filling port 109. Due to the capillary effect, the sealing glue 202 can flow more fully into the cell. This process, together with the protruding structure 110 of the glue frame 105 at the liquid crystal filling port 109, achieves complete sealing of the liquid crystal cell.

[0031] The liquid crystal polarization controller uses the electro-controlled birefringence effect of liquid crystal materials to dynamically change the polarization state of light waves. However, the physical properties of liquid crystal materials are extremely sensitive to temperature. Therefore, the liquid crystal cell 302 needs to be temperature controlled during use. This method is the key guarantee for achieving high precision, high stability and reliable operation of the liquid crystal polarization controller.

[0032] In high-density integrated packaged devices, semiconductor coolers are often used as temperature control units. However, the liquid crystal cell 302 needs to be placed vertically during use, with the bottom surface of the non-flush end of the first substrate 101 and the second substrate 102 facing downwards. The contact area between the bottom surfaces is small and lacks flatness, requiring heat conduction via a metal pad 301. Figure 8 As shown, the second substrate 102 of the liquid crystal cell 302 protrudes from the first substrate 101 and is bonded to the metal pad 301. The metal pad 301 includes a base 3011 and a support back 3012 located outside the base 3011. The bottom surface of the portion of the second substrate 102 protruding from the first substrate 101 is bonded to the upper surface of the base 3011, and the side surface of the portion of the second substrate 102 protruding from the first substrate 101 is bonded to the inner surface of the support back 3012. A groove is formed at the contact point between the inner surface of the support back 3012 and the upper surface of the base 3011. The groove extends through the support back 3012 from front to back, improving the heat dissipation of the liquid crystal cell 302.

[0033] The butterfly-shaped housing 303 adopts the existing housing structure, mainly composed of a base plate, housing, optical fiber tube and pins, which can realize the internal and external interconnection of photoelectric signals. The housing cover plate 305 can cover the butterfly-shaped housing 303. The butterfly-shaped housing 303 and the housing cover plate 305 can realize the sealing protection of internal devices.

[0034] The thermoelectric cooler 306 is the temperature control element of the liquid crystal polarization controller, mainly used for temperature control of the liquid crystal cell 302. The thermoelectric cooler 306 is fixed to the base plate inside the butterfly-shaped housing 303. The thermistor 307, as a temperature sensing unit, together with the thermoelectric cooler 306, forms a closed-loop temperature control system, enabling high-precision temperature regulation of the device. The ceramic substrate 304 is made of AlN material, which has a high thermal conductivity and can achieve temperature uniformity.

[0035] The fiber optic collimator 308 is fixed inside the left and right fiber optic tubes of the butterfly-shaped housing 303 and is mainly used for optical path transmission of the device.

[0036] The installation process of the liquid crystal polarization controller includes: S10. First, fix the semiconductor cooler 306 to the center of the bottom of the butterfly housing 303 by adhesive bonding or soldering, and solder the leads to the corresponding pins of the butterfly housing 303. S20. Next, the thermistor 307 is fixed to the upper right edge of the ceramic substrate 304 by adhesive bonding or soldering. S30. Next, the ceramic substrate 304 is fixed to the surface of the semiconductor cooler 306 by adhesive bonding or soldering. Then, the thermistor 307 is connected to the corresponding pin of the butterfly shell 303 by gold wire bonding, which can be used for external temperature control. S40. After the liquid crystal cell 302 and the metal pad 301 are bonded and cured with glue, multiple liquid crystal cells 302 with different orientation angles are arranged to form a liquid crystal cell array. Then, the metal pad 301 is fixed to the ceramic substrate 304 with glue to prevent the liquid crystal cell 302 from shifting during coupling. The electrodes 104 of each liquid crystal cell 302 are soldered to the corresponding pins of the butterfly tube shell 303 through leads to realize external electrical control. S50. Then, the fiber collimator 308 needs to be fixed to the left and right fiber tubes of the butterfly tube shell 303 by dispensing adhesive. After the fiber light is collimated by the fiber collimator 308 at the input end, it is incident on the liquid crystal cell array. By applying different voltages to the liquid crystal cell 302, the polarization state of the fiber light is precisely modulated, and then the signal is received by the fiber collimator 308 at the output end. S60. Finally, the tube cover plate 305 and the butterfly tube shell 303 are hermetically sealed using a parallel sealing welding process to ensure the long-term stability of the internal environment. A schematic diagram of the encapsulated fiber optic polarization state modulation liquid crystal polarization controller is shown below. Figure 2 As shown.

[0037] The liquid crystal polarization controller in this embodiment can also use a free-space light polarization state modulation mode, and its packaging method is as follows: Figure 3 As shown, its difference from the liquid crystal polarization controller that uses fiber optic polarization state modulation scheme is that: the fiber optic tubes on the left and right sides of the butterfly shell 303 are removed, and the fiber collimator 308 is replaced with an optical window 401, which is fixed on the left and right sides of the butterfly shell 303. Spatial light directly passes through the optical window 401 at the input end and enters the internal liquid crystal cell array. By applying different voltages to the liquid crystal cells 302 in the liquid crystal cell array, the polarization state of free space light can be accurately modulated, and the signal is received through the optical window 401 at the output end.

[0038] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A liquid crystal polarization controller, characterized in that: It includes a liquid crystal cell (302), a tube cover plate (305) and a butterfly tube shell (303). The liquid crystal cell (302) is fixed inside the butterfly tube shell (303), and the tube cover plate (305) covers the butterfly tube shell (303).

2. The liquid crystal polarization controller as described in claim 1, characterized in that: It also includes a ceramic substrate (304), a semiconductor cooler (306), a thermistor (307), and a light transmission device. Multiple liquid crystal cells (302) are arranged to form a liquid crystal cell array and fixed on the ceramic substrate (304). The ceramic substrate (304) is fixed on the upper surface of the semiconductor cooler (306). The thermistor (307) is fixed on the upper surface of the ceramic substrate (304). The thermistor (307) is connected to the corresponding pin of the butterfly shell (303) by gold wire bonding. The light transmission device is fixed on the left and right sides of the butterfly shell (303).

3. The liquid crystal polarization controller as described in claim 2, characterized in that: It also includes a metal pad (301), with a metal pad (301) fixed to the bottom of each liquid crystal cell (302), and the metal pad (301) is fixed on the ceramic substrate (304).

4. The liquid crystal polarization controller as described in claim 2, characterized in that: The optical transmission device is an optical fiber collimator (308) or an optical window (401).

5. The liquid crystal polarization controller as described in claim 2, characterized in that: The liquid crystal cell includes a first substrate (101), a second substrate (102), a spacer (103), an electrode (104), a frame (105), an ITO film (106), and an alignment layer (107). The inner sides of the first substrate (101) and the second substrate (102) are respectively coated with an ITO film (106) and an alignment layer (107) in parallel and opposite directions. The electrode (104) is located at the lower part of the liquid crystal cell. The spacer (103) and the frame (105) are disposed between the first substrate (101) and the second substrate (102). The frame (105) seals the cell thickness supported by the spacer (103) and leaves a liquid crystal filling port (109).

6. The liquid crystal polarization controller as described in claim 5, characterized in that: Anti-reflection films (108) are deposited on the outer sides of the first substrate (101) and the second substrate (102), respectively.

7. The liquid crystal polarization controller as described in claim 5, characterized in that: The plastic frame (105) on both sides of the liquid crystal inlet (109) is provided with an upward protrusion structure (110), the top of which is in close contact with the upper edge of the liquid crystal cell.

8. The liquid crystal polarization controller as described in claim 5, characterized in that: The second substrate (102) is longer than the first substrate (101). The first substrate (101) and the second substrate (102) are parallel and have one end flush. The other end of the second substrate (102) protrudes from the first substrate (101). The electrode (104) is located outside the part of the second substrate (102) that protrudes from the first substrate (101).

9. The liquid crystal polarization controller as described in claim 8, characterized in that: A metal pad (301) is fixed to the bottom of each liquid crystal cell (302). The metal pad (301) is fixed to the ceramic substrate (304). The metal pad (301) includes a base (3011) and a support back (3012) located outside the base (3011). The bottom surface of the second substrate (102) protruding from the first substrate (101) is bonded to the upper surface of the base (3011), and the side surface of the second substrate (102) protruding from the first substrate (101) is bonded to the inner side surface of the support back (3012).

10. The liquid crystal polarization controller as described in claim 9, characterized in that: The inner side of the support backrest (3012) is recessed at the position where it contacts the upper surface of the base (3011) to form a groove, and the groove extends through the support backrest (3012) from front to back.

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