A method and structure for inhibiting energy loss

Abstract

The present application relates to a kind of method and structure for inhibiting energy loss, solve the current liquid crystal polarization grating multiple interface refractive index mismatch, energy loss is serious and so on problem.Structure includes: substrate;Air-substrate interface refractive index matching film plated in one side of substrate, for reducing the Fresnel reflection energy loss of air-substrate interface;Substrate-liquid crystal polarization grating film refractive index matching film plated in the other side of substrate, for reducing the Fresnel reflection energy loss of substrate-liquid crystal polarization grating film interface;Liquid crystal polarization grating film-air refractive index matching film plated in one side of grating film, for reducing the Fresnel reflection energy loss of liquid crystal polarization grating film-air interface, the other side of grating film and substrate-liquid crystal polarization grating film refractive index matching film contact.This structure can significantly improve the energy utilization efficiency of liquid crystal polarization grating, meet the needs of high efficiency, large angle, non-continuity light beam deflection based on liquid crystal polarization grating.

Description

Technical Field

[0001] This invention belongs to the field of non-mechanical beam deflection technology based on liquid crystal polarization gratings, specifically referring to a method and structure for suppressing energy loss. Background Technology

[0002] Beam deflection modules are core components in many optoelectronic information fields such as lidar, laser communication, and active laser imaging. Liquid crystal polarization gratings are a new type of geometric phase element with unique properties such as large aperture, high efficiency, and wide angle. The new beam deflection technology based on liquid crystal polarization gratings can simultaneously achieve the two core indicators of large aperture and wide angle, thus significantly improving the performance of beam deflection technology. This makes it potentially applicable in many defense and national security fields such as satellite laser communication, airborne lidar, mid-wave infrared staring imaging, ToF cameras, laser countermeasures, and laser guidance.

[0003] Currently, most beam deflection technologies based on liquid crystal polarization gratings adopt a cascaded structure, that is, using the cascade of multiple liquid crystal polarization gratings to achieve large-angle, discontinuous beam deflection. This structure has a simple and reliable control strategy and can easily meet the requirements of miniaturization, flexible control, and low power consumption. However, it is precisely this structure that makes the slight difference in the energy utilization efficiency of a single liquid crystal polarization grating seriously affect the final energy utilization efficiency, which is the bottleneck problem for the current application of liquid crystal polarization gratings in engineering.

[0004] In summary, there are three main factors causing energy loss in liquid crystal polarization gratings: 1. Intrinsic energy loss due to higher-order diffraction; 2. Scattering loss due to grating morphology defects; and 3. Fresnel reflection loss introduced by refractive index mismatch at multiple interfaces. Under the premise of suppressing intrinsic energy loss (factor 1) and defects (factor 2), achieving refractive index matching at multiple interfaces of the liquid crystal polarization grating is a crucial issue and a problem that must be solved for its engineering application. Summary of the Invention

[0005] The purpose of this invention is to provide a method and structure for suppressing energy loss, thereby solving the problems of refractive index mismatch and severe energy loss at multiple interfaces of liquid crystal polarization gratings.

[0006] A method for suppressing energy loss includes the following steps:

[0007] Step 1: Deposit an air-substrate interface refractive index matching film and a substrate-liquid crystal polarization grating film refractive index matching film on both sides of the substrate used to support the liquid crystal polarization grating film, respectively. The air-substrate interface refractive index matching film is used to reduce Fresnel reflection energy loss at the air-substrate interface, and the substrate-liquid crystal polarization grating film refractive index matching film is used to reduce Fresnel reflection energy loss at the substrate-liquid crystal polarization grating film interface.

[0008] Step 2: Prepare the liquid crystal polarization grating film on the substrate-liquid crystal polarization grating film refractive index matching film;

[0009] Step 3: Deposit a liquid crystal polarization grating film-air refractive index matching film on the liquid crystal polarization grating film. The liquid crystal polarization grating film-air refractive index matching film is used to reduce Fresnel reflection energy loss at the liquid crystal polarization grating film-air interface.

[0010] A structure for suppressing energy loss includes:

[0011] Substrate, used to support the liquid crystal polarization grating film;

[0012] An air-substrate interface refractive index matching film is deposited on one side of the substrate to reduce Fresnel reflection energy loss at the air-substrate interface.

[0013] A substrate-liquid crystal polarization grating thin film refractive index matching film is deposited on the other side of the substrate to reduce Fresnel reflection energy loss at the substrate-liquid crystal polarization grating thin film interface.

[0014] A liquid crystal polarization grating film-air refractive index matching film is deposited on one side of the liquid crystal polarization grating film, and the other side of the liquid crystal polarization grating film is in contact with the substrate-liquid crystal polarization grating film refractive index matching film. The liquid crystal polarization grating film-air refractive index matching film is used to reduce Fresnel reflection energy loss at the liquid crystal polarization grating film-air interface.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention provides a method and structure for suppressing energy loss, which differs from traditional methods and structures for suppressing energy loss in liquid crystal polarization gratings. Instead, it involves depositing different refractive index matching films between the substrate and the liquid crystal polarization grating, as well as on its sides. A coating method is employed to deposit the liquid crystal polarization grating thin film-air refractive index matching film on the liquid crystal polarization grating. This fundamentally eliminates Fresnel reflection loss introduced by multi-interface refractive index mismatch, thus achieving energy loss suppression of the liquid crystal polarization grating. By implementing this invention, the energy utilization efficiency of the liquid crystal polarization grating can be significantly improved, meeting the requirements for efficient, large-angle, discontinuous beam deflection based on the liquid crystal polarization grating. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a structure for suppressing energy loss according to one embodiment of the present invention;

[0018] Figure 2 This is a flowchart illustrating a method for suppressing energy loss according to another embodiment of the present invention;

[0019] Explanation of reference numerals in the attached figures: 1. Air-substrate interface refractive index matching film; 2. Substrate; 3. Substrate-liquid crystal polarization grating film refractive index matching film; 4. Liquid crystal polarization grating film; 5. Liquid crystal polarization grating film-air refractive index matching film. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] See Figure 1 This embodiment provides a structure for suppressing energy loss. The structure specifically includes an air-substrate interface refractive index matching film 1, a substrate 2, a substrate-liquid crystal polarization grating thin film refractive index matching film 3, and a liquid crystal polarization grating thin film-air refractive index matching film 5.

[0022] The substrate 2 is used to support the liquid crystal polarization grating film 4.

[0023] The air-substrate interface refractive index matching film 1 is deposited on one side of the substrate 2. According to the Fresnel formula, it can be used to reduce Fresnel reflection energy loss at the air-substrate interface.

[0024] The substrate-liquid crystal polarization grating thin film refractive index matching film 3 is deposited on the other side of the substrate 2. According to the Fresnel formula, it can be used to reduce Fresnel reflection energy loss at the substrate-liquid crystal polarization grating thin film interface.

[0025] The liquid crystal polarization grating film-air refractive index matching film 5 is deposited on one side of the liquid crystal polarization grating film 4 by a coating method. The liquid crystal polarization grating film 4 is prepared on the substrate-liquid crystal polarization grating film refractive index matching film 3. Therefore, the other side of the liquid crystal polarization grating film 4 is in close contact with the substrate-liquid crystal polarization grating film refractive index matching film 3. According to the Fresnel formula, the liquid crystal polarization grating film-air refractive index matching film 5 can be used to reduce the Fresnel reflection energy loss at the liquid crystal polarization grating film-air interface.

[0026] Furthermore, the liquid crystal polarization grating film 4 in this embodiment is a liquid crystal film realized based on reactive liquid crystal and geometric phase. The optical axis of the liquid crystal molecules in the liquid crystal polarization grating film 4 changes continuously within one period and satisfies the following relationship:

[0027]

[0028] in, Λ is the optical axis of the liquid crystal molecules in the liquid crystal polarization grating film 4, and Λ is the period of the liquid crystal polarization grating film 4.

[0029] Furthermore, the thickness of the liquid crystal polarization grating film 4 satisfies the half-wave condition: d = λ / (2*Δn), where d is the thickness of the liquid crystal polarization grating film 4, λ is the operating wavelength, and Δn = n e -n o n e and n o These are the unusual light refractive index and the ordinary light refractive index of the liquid crystal molecules, respectively.

[0030] Furthermore, when designing the interface refractive index matching film, the average refractive index of the liquid crystal polarization grating film 4 is obtained according to the following formula:

[0031]

[0032] in, is the average refractive index of the liquid crystal polarization grating film 4.

[0033] Furthermore, the coating methods used in the deposition of the liquid crystal polarization grating thin film-air refractive index matching film 5 include, but are not limited to, magnetron sputtering coating method, vacuum evaporation coating method, ion plating coating method, etc., to ensure that the liquid crystal polarization grating thin film 4 does not deform and does not lose its original function.

[0034] In this embodiment, the air-substrate interface refractive index matching film 1, the substrate-liquid crystal polarization grating film refractive index matching film 3, and the liquid crystal polarization grating film-air refractive index matching film 5 all depend on the wavelength and angle of the incident light. That is, if the wavelength or angle of the incident light is different, the number of layers, refractive index distribution, thickness, and other parameters of the air-substrate interface refractive index matching film 1, the substrate-liquid crystal polarization grating film refractive index matching film 3, and the liquid crystal polarization grating film-air refractive index matching film 5 will be different, and the corresponding deposition processes will be different. The specific correspondence requires precise film structure design.

[0035] This embodiment also provides a specific example of a structure for suppressing energy loss of a liquid crystal polarization grating, and a comparative experiment on energy efficiency was conducted.

[0036] In this example, the period of the liquid crystal polarization grating film 4 is 23.82 μm, the working wavelength is 1064 nm, the deflection angle is 2.56°, and the thickness of the liquid crystal polarization grating film 4 satisfies the half-wave condition d=λ / (2*Δn)=λ / (2*(n e -n o = 4.4μm.

[0037] Substrate 2 is a quartz substrate with a refractive index of 1.44 at a working wavelength of 1064 nm. Under the condition of perpendicular incidence of circularly polarized light, the measured energy transmission efficiency is 93.48%.

[0038] n e =1.61, n o =1.49, Based on this average refractive index The substrate-liquid crystal polarization grating film 4 structure was designed. After the air-substrate interface refractive index matching film 1 and the substrate-liquid crystal polarization grating film refractive index matching film 3 were deposited, the measured energy transmission efficiency was 95.30% under the condition of perpendicular incident circularly polarized light.

[0039] After the liquid crystal polarization grating film 4 was prepared and under the condition of perpendicular incidence of circularly polarized light, the measured energy transmission efficiency was 95.28%.

[0040] After further completing the deposition of the liquid crystal polarization grating thin film-air refractive index matching film 5, the measured energy transmission efficiency under the condition of perpendicular incidence of circularly polarized light is 99.80%.

[0041] Compared with a liquid crystal polarizing grating substrate that has not been coated with air-substrate interface refractive index matching film 1, substrate-liquid crystal polarizing grating film refractive index matching film 3, and liquid crystal polarizing grating film-air refractive index matching film 5, the energy utilization efficiency of this embodiment is improved by 8.4%.

[0042] Compared to a liquid crystal polarization grating substrate that has not undergone liquid crystal polarization grating film-air refractive index matching film 5 deposition, the energy utilization efficiency of this embodiment is improved by 4.7%.

[0043] As can be seen from the above examples, the energy loss suppression structure proposed in this invention significantly improves the energy utilization efficiency of liquid crystal polarization gratings, and will play an important role, especially when used in cascaded structures.

[0044] See Figure 2 In another embodiment, a method for suppressing energy loss is provided, which mainly includes the following steps:

[0045] Step 1: An air-substrate interface refractive index matching film 1 and a substrate-liquid crystal polarization grating film refractive index matching film 3 are deposited on both sides of the substrate 2 used to support the liquid crystal polarization grating film 4, respectively. The air-substrate interface refractive index matching film 1 is used to reduce Fresnel reflection energy loss at the air-substrate interface, and the substrate-liquid crystal polarization grating film refractive index matching film 3 is used to reduce Fresnel reflection energy loss at the substrate-liquid crystal polarization grating film interface. The substrate 2 can be a quartz substrate.

[0046] Step 2: Prepare a liquid crystal polarization grating film 4 on the substrate-liquid crystal polarization grating film refractive index matching film 3;

[0047] Step 3: A liquid crystal polarization grating film-air refractive index matching film 5 is deposited on the liquid crystal polarization grating film 4 using a coating method. This liquid crystal polarization grating film-air refractive index matching film 5 is used to reduce Fresnel reflection energy loss at the liquid crystal polarization grating film-air interface. The coating method can be any one of magnetron sputtering, vacuum evaporation, or ion plating to ensure that the liquid crystal polarization grating film 4 does not deform and retains its original function.

[0048] Furthermore, the liquid crystal polarization grating film 4 in this embodiment is a liquid crystal film realized based on reactive liquid crystal and geometric phase. The optical axis of the liquid crystal molecules in the liquid crystal polarization grating film 4 changes continuously within one period and satisfies the following relationship:

[0049]

[0050] in, Λ is the optical axis of the liquid crystal molecules in the liquid crystal polarization grating film 4, and Λ is the period of the liquid crystal polarization grating film 4.

[0051] Furthermore, the thickness of the liquid crystal polarization grating film 4 satisfies the half-wave condition: d = λ / (2*Δn), where d is the thickness of the liquid crystal polarization grating film 4, λ is the operating wavelength, and Δn = n e -n o n e and n o These are the unusual light refractive index and the ordinary light refractive index of the liquid crystal molecules, respectively.

[0052] Furthermore, when designing the interface refractive index matching film, the average refractive index of the liquid crystal polarization grating film 4 is obtained according to the following formula:

[0053]

[0054] in, is the average refractive index of the liquid crystal polarization grating film 4.

[0055] The present invention proposes a method and structure for suppressing energy loss in liquid crystal polarization gratings, which differs from traditional methods and structures for suppressing energy loss in liquid crystal polarization gratings. Instead, it involves depositing different refractive index matching films between the substrate and the liquid crystal polarization grating, as well as on its sides. A coating method is employed to deposit the liquid crystal polarization grating thin film-air refractive index matching film on the liquid crystal polarization grating. This fundamentally eliminates Fresnel reflection loss introduced by multi-interface refractive index mismatch, thereby achieving energy loss suppression in the liquid crystal polarization grating. By implementing this invention, the energy utilization efficiency of the liquid crystal polarization grating can be significantly improved, meeting the requirements for efficient, large-angle, discontinuous beam deflection based on the liquid crystal polarization grating.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for suppressing energy loss, characterized in that, Includes the following steps: Step 1: An air-substrate interface refractive index matching film (1) and a substrate-liquid crystal polarization grating film refractive index matching film (3) are deposited on both sides of the substrate (2) used to support the liquid crystal polarization grating film (4). The air-substrate interface refractive index matching film (1) is used to reduce Fresnel reflection energy loss at the air-substrate interface, and the substrate-liquid crystal polarization grating film refractive index matching film (3) is used to reduce Fresnel reflection energy loss at the substrate-liquid crystal polarization grating film interface. Step 2: Prepare the liquid crystal polarization grating film (4) on the substrate-liquid crystal polarization grating film refractive index matching film (3); Step 3: A liquid crystal polarization grating film-air refractive index matching film (5) is deposited on the liquid crystal polarization grating film (4) using any one of the following methods: magnetron sputtering, vacuum evaporation, or ion plating. The liquid crystal polarization grating film-air refractive index matching film (5) is used to reduce Fresnel reflection energy loss at the liquid crystal polarization grating film-air interface. The thickness d of the liquid crystal polarization grating film (4) satisfies the half-wave condition: d = λ / (2*Δn) Where λ is the operating wavelength, Δn = n e -n o n e and n o These are the unusual light refractive index and the ordinary light refractive index of the liquid crystal molecules, respectively. The average refractive index of the liquid crystal polarization grating film (4) is: in, The average refractive index of the liquid crystal polarization grating film (4) is given.

2. The method for suppressing energy loss according to claim 1, characterized in that, The optical axis of the liquid crystal molecules in the liquid crystal polarization grating film (4) changes continuously within one period and satisfies the following relationship: in, Λ is the optical axis of the liquid crystal molecules in the liquid crystal polarization grating film (4), and Λ is the period of the liquid crystal polarization grating film (4).

3. A structure for suppressing energy loss, characterized in that, include: Substrate (2) is used to support the liquid crystal polarization grating film (4); An air-substrate interface refractive index matching film (1) is deposited on one side of the substrate (2) to reduce Fresnel reflection energy loss at the air-substrate interface. A substrate-liquid crystal polarization grating thin film refractive index matching film (3) is deposited on the other side of the substrate (2) to reduce Fresnel reflection energy loss at the substrate-liquid crystal polarization grating thin film interface; A liquid crystal polarization grating thin film-air refractive index matching film (5) is deposited on one side of the liquid crystal polarization grating thin film (4) by any one of magnetron sputtering, vacuum evaporation, or ion plating. The other side of the liquid crystal polarization grating thin film (4) is in contact with the substrate-liquid crystal polarization grating thin film refractive index matching film (3). The liquid crystal polarization grating thin film-air refractive index matching film (5) is used to reduce Fresnel reflection energy loss at the liquid crystal polarization grating thin film-air interface. The thickness d of the liquid crystal polarization grating film (4) satisfies the half-wave condition: d = λ / (2*Δn) Where λ is the operating wavelength, Δn = n e -n o n e and n o These are the unusual light refractive index and the ordinary light refractive index of the liquid crystal molecules, respectively. The average refractive index of the liquid crystal polarization grating film (4) is: in, The average refractive index of the liquid crystal polarization grating film (4) is given.

4. The structure for suppressing energy loss according to claim 3, characterized in that, The optical axis of the liquid crystal molecules in the liquid crystal polarization grating film (4) changes continuously within one period and satisfies the following relationship: in, Λ is the optical axis of the liquid crystal molecules in the liquid crystal polarization grating film (4), and Λ is the period of the liquid crystal polarization grating film (4).

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