Method and structure for suppressing energy loss

Abstract

The invention relates to a method and a structure for inhibiting energy loss, which solve the problems of mismatching of multi-interface refractive indexes, serious energy loss and the like of the existing liquid crystal polarization grating. The structure comprises a substrate; the air-substrate interface refractive index matching film is plated on one side of the substrate and is used for reducing Fresnel reflection energy loss of an air-substrate interface; the substrate-liquid crystal polarization grating film refractive index matching film is plated on the other side of the substrate and is used for reducing Fresnel reflection energy loss of a substrate-liquid crystal polarization grating film interface; the liquid crystal polarization grating film-air refractive index matching film is plated on one side of the grating film and is used for reducing Fresnel reflection energy loss of a liquid crystal polarization grating film-air interface, and the other side of the grating film is in contact with the substrate-liquid crystal polarization grating film refractive index matching film. According to the structure, the energy utilization efficiency of the liquid crystal polarization grating can be remarkably improved, and the requirements of efficient, large-angle and non-continuous light beam deflection based on the liquid crystal polarization grating are met.

Description

Technical Field

[0001] The invention belongs to the technical field of non-mechanical light beam deflection based on liquid crystal polarization grating, and specifically refers to a method and structure for suppressing energy loss. Background Art

[0002] The beam deflection module is one of the core components in many optoelectronic information fields such as laser radar, laser communication, and laser active imaging. The liquid crystal polarization grating is 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 grating can take into account the two core indicators of large aperture and large angle at the same time, so it can greatly improve the performance of beam deflection technology. This makes it have potential application possibilities in many national defense and national security fields such as satellite laser communication, airborne laser radar, medium-wave infrared staring imaging, ToF camera, laser confrontation, laser guidance, etc.

[0003] At present, most of the beam deflection technologies based on liquid crystal polarization gratings adopt a cascade structure, that is, the cascade of multiple liquid crystal polarization gratings is used to achieve large-angle, non-continuous beam deflection. This structural control strategy is simple and reliable, and can easily meet the requirements of lightweight 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 will seriously affect the final energy utilization efficiency, which is the bottleneck problem for the current engineering application of liquid crystal polarization gratings.

[0004] In summary, there are three main factors that cause energy loss in liquid crystal polarization gratings: 1. Intrinsic energy loss caused by high-order diffraction; 2. Scattering loss caused by grating morphology defects; 3. Fresnel reflection loss introduced by multi-interface refractive index mismatch. On the premise of achieving intrinsic energy loss suppression (factor 1) and defect suppression (factor 2), how to achieve multi-interface refractive index matching of liquid crystal polarization gratings is an issue that cannot be ignored, and it is also a difficult problem that must be solved for the engineering application of liquid crystal polarization gratings. Summary of the invention

[0005] The purpose of the present invention is to provide a method and structure for suppressing energy loss, so as to solve the problems of mismatched refractive index of multiple interfaces of liquid crystal polarization grating and serious energy loss.

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

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

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

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

[0010] A structure for suppressing energy loss, comprising:

[0011] A substrate for supporting the liquid crystal polarization grating film;

[0012] An air-substrate interface refractive index matching film, plated on one side of the substrate, for reducing Fresnel reflection energy loss at the air-substrate interface;

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

[0014] A liquid crystal polarization grating film-air refractive index matching film is plated 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 the Fresnel reflection energy loss of the liquid crystal polarization grating film-air interface.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention provides a method and structure for suppressing energy loss, which is different from the traditional method and structure for suppressing energy loss of liquid crystal polarization grating. Instead, different refractive index matching films are plated between the substrate and the liquid crystal polarization grating and on the sides thereof, and a coating method is adopted to plate the liquid crystal polarization grating thin film-air refractive index matching film on the liquid crystal polarization grating, which can fundamentally eliminate the Fresnel reflection loss introduced by the multi-interface refractive index mismatch and realize the suppression of energy loss of the liquid crystal polarization grating. By implementing the present invention, the energy utilization efficiency of the liquid crystal polarization grating can be significantly improved, meeting the needs of high-efficiency, large-angle, and discontinuous light beam deflection based on the liquid crystal polarization grating. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0018] Figure 2 A flow chart of a method for suppressing energy loss according to another embodiment of the present invention;

[0019] Explanation of the accompanying drawings: 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 DESCRIPTION

[0020] In order 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 also Figure 1 This embodiment provides a structure for suppressing energy loss, which specifically includes an air-substrate interface refractive index matching film 1, a substrate 2, a substrate-liquid crystal polarization grating film refractive index matching film 3 and a liquid crystal polarization grating 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 plated on one side of the substrate 2. According to the Fresnel formula, it can be used to reduce the Fresnel reflection energy loss at the air-substrate interface.

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

[0025] The liquid crystal polarization grating film-air refractive index matching film 5 is coated 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. It can be seen from the Fresnel formula that the liquid crystal polarization grating film-air refractive index matching film 5 can be used to reduce the Fresnel reflection energy loss of 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 based on reactive liquid crystal and geometric phase. The optical axis of the liquid crystal molecules of the liquid crystal polarization grating film 4 changes continuously within a period and satisfies the relationship:

[0027]

[0028] in, is the optical axis of the liquid crystal molecules of 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 They are the extraordinary refractive index and ordinary 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 method used when coating the liquid crystal polarization grating film-air refractive index matching film 5 includes but is not limited to a magnetron sputtering coating method, a vacuum evaporation coating method, an ion plating coating method, etc., to ensure that the liquid crystal polarization grating film 4 does not deform and does not lose its original function.

[0034] The air-substrate interface refractive index matching film 1, substrate-liquid crystal polarization grating film refractive index matching film 3, and liquid crystal polarization grating film-air refractive index matching film 5 in this embodiment all depend on the wavelength and angle of the incident light, that is, 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, substrate-liquid crystal polarization grating film refractive index matching film 3, and liquid crystal polarization grating film-air refractive index matching film 5 are different, and the corresponding plating processes are different. The specific corresponding relationship requires precise film layer structure design.

[0035] This embodiment also provides a specific example of a structure for suppressing the energy loss of a liquid crystal polarization grating, and conducts an energy efficiency comparison experiment.

[0036] In this example, the period of the liquid crystal polarization grating film 4 is 23.82 μm, the operating 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] The substrate 2 is a quartz substrate with a refractive index of 1.44 at an operating wavelength of 1064 nm. Under the condition of vertical incidence of circularly polarized light, the energy transmission efficiency is measured to be 93.48%.

[0038] n e =1.61,n o =1.49, According to this average refractive index The structure of substrate-liquid crystal polarization grating film 4 is designed. After coating the air-substrate interface refractive index matching film 1 and the substrate-liquid crystal polarization grating film refractive index matching film 3, the energy transmission efficiency is measured to be 95.30% under the condition of vertical incidence of circularly polarized light.

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

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

[0041] Compared with the liquid crystal polarization grating substrate without the air-substrate interface refractive index matching film 1, substrate-liquid crystal polarization grating film refractive index matching film 3, and liquid crystal polarization grating film-air refractive index matching film 5, the energy utilization efficiency of this embodiment is improved by 8.4%.

[0042] Compared with the liquid crystal polarization grating substrate without the liquid crystal polarization grating film-air refractive index matching film 5 coating, the energy utilization efficiency of this embodiment is improved by 4.7%.

[0043] It can be seen from the above examples that the structure for suppressing energy loss proposed in the present invention significantly improves the energy utilization efficiency of the liquid crystal polarization grating, and plays an important role especially when used in a cascade structure.

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

[0045] Step 1: coating an air-substrate interface refractive index matching film 1 and a substrate-liquid crystal polarization grating film refractive index matching film 3 on both sides of a substrate 2 for supporting a liquid crystal polarization grating film 4, wherein the air-substrate interface refractive index matching film 1 is used to reduce the 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 the Fresnel reflection energy loss at the substrate-liquid crystal polarization grating film interface; wherein the substrate 2 may be a quartz substrate;

[0046] Step 2: preparing a liquid crystal polarization grating film 4 on a 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 plated on the liquid crystal polarization grating film 4 by a coating method, and the liquid crystal polarization grating film-air refractive index matching film 5 is used to reduce the Fresnel reflection energy loss of the liquid crystal polarization grating film-air interface. The coating method can be any one of a magnetron sputtering coating method, a vacuum evaporation coating method and an ion plating coating method to ensure that the liquid crystal polarization grating film 4 does not deform and does not lose its original function.

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

[0049]

[0050] in, is the optical axis of the liquid crystal molecules of 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 They are the extraordinary refractive index and ordinary 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 method and structure for suppressing the energy loss of a liquid crystal polarization grating proposed in the present invention are different from the conventional method and structure for suppressing the energy loss of a liquid crystal polarization grating. Instead, different refractive index matching films are plated between the substrate and the liquid crystal polarization grating and on the sides thereof, and a coating method is adopted to plate the liquid crystal polarization grating thin film-air refractive index matching film on the liquid crystal polarization grating, which can fundamentally eliminate the Fresnel reflection loss introduced by the multi-interface refractive index mismatch and realize the suppression of the energy loss of the liquid crystal polarization grating. By implementing the present invention, the energy utilization efficiency of the liquid crystal polarization grating can be significantly improved, meeting the needs of high-efficiency, large-angle, and non-continuous light beam deflection based on the liquid crystal polarization grating.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for suppressing energy loss, characterized in that: The following steps are involved: Step 1: coating an air-substrate interface refractive index matching film (1) and a substrate-liquid crystal polarization grating film refractive index matching film (3) on both sides of a substrate (2) used for supporting a liquid crystal polarization grating film (4), respectively, wherein the air-substrate interface refractive index matching film (1) is used to reduce the 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 the Fresnel reflection energy loss at the substrate-liquid crystal polarization grating film interface; Step 2: preparing the liquid crystal polarization grating film (4) on the substrate-liquid crystal polarization grating film refractive index matching film (3); Step 3: coating a liquid crystal polarization grating film-air refractive index matching film (5) on the liquid crystal polarization grating film (4), wherein the liquid crystal polarization grating film-air refractive index matching film (5) is used to reduce the Fresnel reflection energy loss at the liquid crystal polarization grating film-air interface.

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

3. A method for suppressing energy loss according to claim 1 or 2, characterized in that: 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 They are the extraordinary refractive index and ordinary refractive index of the liquid crystal molecules respectively.

4. A method for suppressing energy loss according to claim 3, characterized in that: The average refractive index of the liquid crystal polarization grating film (4) is: in, is the average refractive index of the liquid crystal polarization grating film (4).

5. A structure for suppressing energy loss, characterized in that: include: A substrate (2) used for supporting a liquid crystal polarization grating film (4); An air-substrate interface refractive index matching film (1) is plated on one side of the substrate (2) and is used to reduce Fresnel reflection energy loss at the air-substrate interface; A substrate-liquid crystal polarization grating film refractive index matching film (3) is plated on the other side of the substrate (2) and is used to reduce Fresnel reflection energy loss at the interface of the substrate-liquid crystal polarization grating film; A liquid crystal polarization grating film-air refractive index matching film (5) is plated on one side of the liquid crystal polarization grating film (4), and the other side of the liquid crystal polarization grating film (4) is in contact with the substrate-liquid crystal polarization grating film refractive index matching film (3). The liquid crystal polarization grating film-air refractive index matching film (5) is used to reduce the Fresnel reflection energy loss of the liquid crystal polarization grating film-air interface.

6. The structure for suppressing energy loss according to claim 5, characterized in that: The optical axis of the liquid crystal molecules of the liquid crystal polarization grating film (4) changes continuously within one period and satisfies the relationship: in, is the liquid crystal molecule optical axis of the liquid crystal polarization grating film (4), and Λ is the period of the liquid crystal polarization grating film (4).

7. A structure for suppressing energy loss according to claim 5 or 6, characterized in that: 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 They are the extraordinary refractive index and ordinary refractive index of the liquid crystal molecules respectively.

8. The structure for suppressing energy loss according to claim 7, characterized in that: The average refractive index of the liquid crystal polarization grating film (4) is: in, is the average refractive index of the liquid crystal polarization grating film (4).

Images