Polarization beam splitter and optical equipment with same

Abstract

The utility model discloses a polarization beam splitter and optical equipment with the same, and relates to the technical field of optical devices. The polarization beam splitter comprises a protective layer; the diffraction grating layer is located on the protection layer, the diffraction grating layer comprises optical units which are arranged at equal intervals, each optical unit comprises at least two polarization modulation layers which are sequentially stacked in the incident beam transmission direction, and the grating period of the diffraction grating layer ranges from 570 nanometers to 590 nanometers. By the adoption of the polarization beam splitter, incident beams in different polarization states can be spatially separated in the transmission diffraction order through the hierarchical structure, the structure is simple, the complexity of an optical system is remarkably reduced, and efficient integration is facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of optical devices, and in particular to a polarization beam splitter and an optical device having the same. Background Art

[0002] As an important spectroscopic element, the polarization beam splitter can split the incident light beam into two orthogonal polarization directions: transverse electric polarization (TE) and transverse magnetic polarization (TM), and guide these outgoing light beams to propagate along different paths. It can be widely used in optical communications, quantum logic operations, sensors, precision measurement and other fields.

[0003] At present, the polarization beam splitters in related technologies mainly include polarization beam splitters based on birefringence effect, photonic crystal polarization beam splitters and optical waveguide polarization beam splitters, etc. However, the polarization beam splitters based on birefringence effect require sufficient thickness to separate the two polarized lights, which is not suitable for optical path integration. Photonic crystal polarization beam splitters and optical waveguide polarization beam splitters require additional coupling devices to guide the incident light beam, and the optical system structure is complex. Utility Model Content

[0004] In view of the above-mentioned defects or deficiencies in the related art, it is desired to provide a polarization beam splitter and an optical device having the same, which has a simple structure and is easy to integrate.

[0005] In a first aspect, the present application provides a polarization beam splitter, comprising:

[0006] protective layer;

[0007] A diffraction grating layer located on the protective layer includes optical units arranged at equal intervals, each optical unit includes at least two polarization modulation layers stacked in sequence along the transmission direction of the incident light beam, and a grating period Λ of the diffraction grating layer is 570 nanometers to 590 nanometers.

[0008] Optionally, in some embodiments of the present application, the two polarization modulation layers include a first polarization modulation layer and a second polarization modulation layer, and both the first polarization modulation layer and the second polarization modulation layer are columnar structures.

[0009] Optionally, in some embodiments of the present application, the column structure includes a cylinder, a prism or a frustum.

[0010] Optionally, in some embodiments of the present application, the polarization modulation layer located at the top of the two polarization modulation layers is a tantalum pentoxide layer, and the polarization modulation layer located at the bottom is a magnesium fluoride layer.

[0011] Optionally, in some embodiments of the present application, the duty ratio of the polarization modulation layer located at the top and the duty ratio of the polarization modulation layer located at the bottom are both 0.5 to 0.55.

[0012] Optionally, in some embodiments of the present application, the polarization modulation layer located on the top has a thickness of 900 nanometers to 1020 nanometers;

[0013] And / or, the polarization modulation layer at the bottom has a thickness of 150 nanometers to 420 nanometers.

[0014] Optionally, in some embodiments of the present application, the thickness of the protective layer is greater than 10 microns.

[0015] Optionally, in some embodiments of the present application, the central wavelength λ of the incident light beam is 540 nm to 560 nm, and

[0016] In a second aspect, the present application provides an optical device, comprising the polarization beam splitter described in any one of the first aspects.

[0017] Optionally, in some embodiments of the present application, the optical device is a virtual reality display device, an augmented reality display device, or a mixed reality display device.

[0018] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0019] Embodiments of the present application provide a polarization beam splitter and an optical device having the same. An incident light beam is spatially modulated by providing a diffraction grating layer on a protective layer. The grating period is 570 to 590 nanometers. This means that the diffraction grating layer can interact with the incident light field, changing the electromagnetic field transmission form of the incident light field on the surface of the diffraction grating layer to achieve polarization control. At the same time, at least two polarization modulation layers stacked in the diffraction grating layer can transmit the light beam. Thus, the hierarchical structure can spatially separate incident light beams of different polarization states at the transmission diffraction order. This simple structure significantly reduces the complexity of the optical system and facilitates efficient integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the three-dimensional structure of a polarization beam splitter provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of a single-period three-dimensional structure of a polarization beam splitter provided in an embodiment of the present application;

[0022] Figure 3 A schematic diagram of a single-period three-dimensional structure of another polarization beam splitter provided in an embodiment of the present application;

[0023] Figure 4 A method provided in the embodiment of this application Figure 2 Side view of the single-period three-dimensional structure shown;

[0024] Figure 5 A diffraction efficiency diagram corresponding to a polarization beam splitter with different structural parameters provided in an embodiment of the present application;

[0025] Figure 6 A diffraction efficiency diagram corresponding to another polarization beam splitter with different structural parameters provided in an embodiment of the present application;

[0026] Figure 7 A structural block diagram of an optical device provided in an embodiment of the present application;

[0027] Figure 8 A schematic flow chart of a light splitting method using a polarization beam splitter provided in an embodiment of the present application;

[0028] Figure 9 The embodiment of the present application provides an incident light beam from Figure 2 Schematic diagram of diffraction results of the single-periodic three-dimensional structure shown at normal incidence;

[0029] Figure 10 A method provided in the embodiment of this application Figure 8 Bottom view of the diffraction result shown;

[0030] Figure 11 A schematic flow chart of a method for manufacturing a polarization beam splitter provided in an embodiment of the present application.

[0031] Reference numerals:

[0032] 1-polarization beam splitter, 11-protective layer, 12-diffraction grating layer, 121-optical unit, a1-first polarization modulation layer, a2-second polarization modulation layer, b1-polarization modulation layer at the top, b2-polarization modulation layer at the bottom, f-duty ratio, Λ-grating period, h1-thickness of the polarization modulation layer at the top, h2-thickness of the polarization modulation layer at the bottom, h3-thickness of the protective layer. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0034] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other. Figures 1 to 11 The polarization beam splitter provided in the embodiments of the present application and the optical device, the splitting method, and the manufacturing method thereof are described in detail.

[0035] Please refer to Figure 1, which is a schematic diagram of the three-dimensional structure of a polarization beam splitter provided in an embodiment of the present application. The polarization beam splitter 1 includes a protective layer 11 and a diffraction grating layer 12 located on the protective layer 11. The diffraction grating layer 12 includes optical units 121 arranged at equal intervals, wherein the optical units 121 include at least two polarization modulation layers stacked in sequence along the transmission direction of the incident light beam, that is, the number of polarization modulation layers includes but is not limited to two, three, and four, and the grating period Λ of the diffraction grating layer 12 is 570 nanometers to 590 nanometers. That is, according to the grating equation, the grating period Λ determines the dimensional parameters such as the spacing between adjacent optical units. Therefore, the diffraction grating layer 12 can interact with the incident light field to change the electromagnetic field transmission form of the incident light field on the surface of the diffraction grating layer 12, thereby achieving polarization control. At the same time, the light beam can be transmitted through at least two polarization modulation layers to spatially separate the incident light beams of different polarization states in the transmission diffraction order, resulting in a simple structure.

[0036] In an example, see Figure 2 The single-period three-dimensional structure diagram of the polarization beam splitter shown in the figure, the at least two polarization modulation layers include but are not limited to the first polarization modulation layer a1 and the second polarization modulation layer a2, etc., and the first polarization modulation layer a1 and the second polarization modulation layer a2 can both be cylindrical structures. Further, the cylindrical structure includes a cylinder, a prism or a frustum, for example Figure 2 The first polarization modulation layer a1 and the second polarization modulation layer a2 shown in the figure can both be cylinders. In this case, the bottom areas of the upper and lower cylinders are the same. The advantage of this arrangement is that the structure is simple and the processing is convenient. For another example, the first polarization modulation layer a1 and the second polarization modulation layer a2 can both be prisms, and the prisms include but are not limited to triangular prisms, square prisms and pentagonal prisms. For another example, Figure 3 The first polarization modulation layer a1 and the second polarization modulation layer a2 shown can also be frustums. In this case, the bottom area of ​​the upper frustum is equal to the top area of ​​the lower frustum. The advantage of this setting is that it can be flexibly selected according to actual usage requirements and is more diversified.

[0037] In another example, the polarization modulation layer b1 at the top of the at least two polarization modulation layers in the embodiment of the present application may be a tantalum pentoxide (Ta2O5) layer, and the polarization modulation layer b2 at the bottom may be a magnesium fluoride (MgF2) layer. This allows the high refractive index and low dispersion properties of tantalum pentoxide to be utilized to modulate the effective refractive index of the grating, while the good polarization properties of magnesium fluoride are comprehensively utilized to enhance the light transmittance of the diffraction grating layer 12 and improve the diffraction efficiency. Figure 2For example, the top polarization modulation layer b1 corresponds to the first polarization modulation layer a1, while the bottom polarization modulation layer b2 corresponds to the second polarization modulation layer a2. Specifically, the first polarization modulation layer a1 is a tantalum pentoxide layer, and the second polarization modulation layer a2 is a magnesium fluoride layer. Both the top polarization modulation layer b1 and the bottom polarization modulation layer b2 can have a cylindrical structure. For details, please refer to the previous description and will not be repeated here.

[0038] Furthermore, for example Figure 4 As shown, in the embodiment of the present application, the duty ratio of the polarization modulation layer b1 at the top and the duty ratio of the polarization modulation layer b2 at the bottom are both 0.5 to 0.55, where f represents the duty ratio. The advantage of this setting is that the photoresist width can be controlled by adjusting the exposure dose and exposure time during the processing and manufacturing process with the same duty ratio, and the preparation can be completed by one exposure, development and etching, which greatly improves the production efficiency. At the same time, the duty ratio range with a value in the middle can also give the production process a larger fault tolerance space.

[0039] Still see Figure 4 In some embodiments of the present application, the thickness h1 of the polarization modulation layer b1 located at the top can be 900 nanometers to 1020 nanometers, and the thickness h2 of the polarization modulation layer b2 located at the bottom can be 150 nanometers to 420 nanometers; for example, in other embodiments of the present application, the thickness h1 of the polarization modulation layer b1 located at the top can be 900 nanometers to 1020 nanometers; for example, in still other embodiments of the present application, the thickness h2 of the polarization modulation layer b2 located at the bottom can be 150 nanometers to 420 nanometers.

[0040] Next, we will describe the protective layer 11. In the present embodiment, the protective layer 11 can be, for example, silica glass or glass-ceramics. This provides excellent optical properties such as high-temperature resistance, a low thermal expansion coefficient, and high transmittance, thereby improving the stability and diffraction efficiency of the diffraction grating layer 12. Furthermore, the thickness h3 of the protective layer 11 can be greater than 10 microns, thereby ensuring the structural strength of the diffraction grating layer 12.

[0041] In other embodiments of the present application, the central wavelength λ of the incident light beam in all the above embodiments may be 540 nm to 560 nm, and The incident angle is normal incidence from the diffraction grating layer 12, which is conducive to optical system integration. The central wavelength λ range covers the common operating wavelength of green lasers, and high-efficiency diffraction can be achieved within the operating wavelength range of 20 nanometers, ensuring wavelength compatibility. Specifically, when the incident light beam passes through the diffraction grating layer 12 and undergoes diffraction, different diffraction orders can be divided according to the central wavelength λ, grating period Λ, and incident angle. Since the two-dimensional grating is an extension of the one-dimensional grating, the diffraction equation of the two-dimensional grating is expressed as follows, that is,

[0042] sin θ m，n cosφ m，n =sinθcosφ+mλ / Λ x (1)

[0043] sin θ m，n sinφ m，n =sinθsinφ+nλ / Λ y (2)

[0044] In equations (1) and (2), φ represents the azimuth angle of the incident light beam, and θ represents the polar angle of the incident light beam; m，n Indicates the azimuth angle of the diffracted light at the (m, n) order, θ m，n represents the polar angle corresponding to the diffracted light at the (m, n) order; Λ x represents the period of the diffraction grating layer in the x direction, Λ y Indicates the period of the diffraction grating layer in the y direction. In order to facilitate manufacturing and meet the symmetry of the grating structure, Λ is designed. x =Λ y ;λ represents the center wavelength.

[0045] When satisfied When , the transmission diffraction order is only (1, 0), (-1, 0), (0, 1), (0, -1) and (0, 0) five diffraction orders, and the fewer the diffraction orders, the higher the energy utilization rate, which is more conducive to using phase to control the diffraction efficiency distribution. By selecting the material of the polarization modulation layer and changing the structural parameters of the diffraction grating layer, the phase of the incident light field in the diffraction grating layer can be changed, and the flow state of the electromagnetic field on the surface of the diffraction grating layer also changes accordingly, thereby manipulating the electric field vector distribution and the magnetic field vector distribution to achieve light modulation. For example Figure 5 and Figure 6 The following are the diffraction efficiency diagrams corresponding to polarization beam splitters with different structural parameters: Figure 5 The polarization beam splitter grating period Λ=577nm, the central wavelength λ=550nm, the protective layer thickness h3=50μm, the duty ratio f=0.52, and Figure 6The polarization beam splitter grating period Λ = 580 nanometers, the central wavelength λ = 560 nanometers, the protective layer thickness h3 = 50 microns, and the duty ratio f = 0.535. It can be seen from the figure that when the transverse magnetic polarized light (TM) is incident from the diffraction grating layer 12 under normal incidence conditions, the diffraction efficiency η of the (0, -1) order and (0, 1) order transmission diffraction orders are both greater than 35%, and when the transverse electric polarized light (TE) is incident from the diffraction grating layer 12 under normal incidence conditions, the diffraction efficiency η of the (1, 0) order and (-1, 0) order transmission diffraction orders are also greater than 35%. In addition, the test results show that when the incident light beam with a central wavelength λ of 550 nanometers is normally incident from the diffraction grating layer 12, the transmission diffraction energy of TM is mainly concentrated in the (0, -1) order and (0, 1) order transmission diffraction orders, and the energy of each order can reach 40.16%, while the transmission diffraction energy of TE is mainly concentrated in the (1, 0) order and (-1, 0) order transmission diffraction orders, and the energy of each order can reach 40.16%. The diffraction efficiency utilization rate is as high as 80%, realizing the spatial orthogonal decomposition of the polarization state of light.

[0046] The polarization beam splitter provided in an embodiment of the present application spatially modulates an incident light beam by providing a diffraction grating layer on a protective layer. The grating period is 570 to 590 nanometers. This means that the diffraction grating layer can interact with the incident light field, changing the electromagnetic field transmission form of the incident light field on the surface of the diffraction grating layer, thereby achieving polarization control. At the same time, at least two polarization modulation layers stacked in the diffraction grating layer can transmit the light beam. Thus, the hierarchical structure can spatially separate incident light beams of different polarization states at the transmission diffraction order. This simple structure significantly reduces the complexity of the optical system and facilitates efficient integration.

[0047] Based on the above embodiments, the present application provides an optical device. Figure 7 , which is a structural block diagram of an optical device provided in an embodiment of the present application, the optical device 2 may include Figures 1 to 6 Corresponding to the polarization beam splitter 1 in any embodiment. In addition, the optical device 2 may further include a filter (not shown in the figure) to filter out stray light and obtain an incident light beam with a central wavelength λ of 540 nm to 560 nm.

[0048] Furthermore, in the embodiment of the present application, the optical device 2 may be a virtual reality (VR) display device, an augmented reality (AR) display device, or a mixed reality (MR) display device.

[0049] It should be noted that, for the description of the same contents in this embodiment as in other embodiments, reference can be made to the description in other embodiments and will not be repeated here.

[0050] In the optical device provided in the embodiment of the present application, the polarization beam splitter spatially modulates the incident light beam by providing a diffraction grating layer on the protective layer. The grating period is 570 nanometers to 590 nanometers. That is, the diffraction grating layer can interact with the incident light field, changing the electromagnetic field transmission form of the incident light field on the surface of the diffraction grating layer, thereby achieving polarization control. At the same time, at least two polarization modulation layers stacked in the diffraction grating layer can transmit the light beam, so that the hierarchical structure can be used to spatially separate the incident light beams with different polarization states in the transmission diffraction order. The structure is simple, significantly reduces the complexity of the optical system, and facilitates efficient integration.

[0051] Based on the above embodiments, the present invention provides a method for splitting light using a polarization beam splitter. Figure 8 , which is a schematic flow chart of a polarization beam splitter method provided in an embodiment of the present application. The polarization beam splitter method can be used for Figures 1 to 6 Corresponding to the polarization beam splitter 1 in any embodiment, the light splitting method specifically includes the following steps:

[0052] S101 , receiving an incident light beam irradiated on a surface of an optical unit, where the incident light beam includes transverse electric polarized light and transverse magnetic polarized light.

[0053] S102 , spatially separating the incident light beam in the transmission diffraction order through at least two polarization modulation layers in the optical unit to obtain transverse electric polarized light and transverse magnetic polarized light.

[0054] For example, Figure 9 and Figure 10 As shown, the incident beam containing TE and TM (i.e. Figure 9 The TE / TM incident light in the optical fiber can be spatially separated in the transmission diffraction order after passing through the polarization beam splitter 1, and the energy of TM is mainly concentrated in the (0,-1) order and (0,1) order transmission diffraction orders, and the energy of TE is mainly concentrated in the (1,0) order and (-1,0) order transmission diffraction orders, realizing high-efficiency transmission-type orthogonal polarization decomposition and optical beam splitting functions.

[0055] It should be noted that, for the description of the same contents in this embodiment as in other embodiments, reference can be made to the description in other embodiments and will not be repeated here.

[0056] The polarization beam splitter spectrometry method provided in the embodiments of the present application utilizes a diffraction grating layer disposed on a protective layer of the polarization beam splitter to spatially modulate an incident light beam. The grating period is 570 to 590 nanometers. This means that the diffraction grating layer can interact with the incident light field, changing the electromagnetic field transmission form of the incident light field on the surface of the diffraction grating layer to achieve polarization control. Furthermore, at least two polarization modulation layers stacked in the diffraction grating layer can transmit the light beam. Thus, the hierarchical structure can spatially separate incident light beams of different polarization states at the transmission diffraction order. This simple structure significantly reduces the complexity of the optical system and facilitates efficient integration.

[0057] Based on the above embodiments, the present invention provides a method for manufacturing a polarization beam splitter. Figure 11 , which is a flow chart of a method for manufacturing a polarization beam splitter provided in an embodiment of the present application. The manufacturing method can be used to manufacture the polarization beam splitter 1 in any of the aforementioned embodiments. The manufacturing method specifically includes the following steps:

[0058] S201, providing a protective layer.

[0059] For example, in the embodiment of the present application, the protective layer 11 can be made of silica glass or glass-ceramics, which exhibits excellent optical properties such as high-temperature resistance, a low thermal expansion coefficient, and high transmittance, thereby helping to improve the stability and diffraction efficiency of the subsequently fabricated diffraction grating layer 12. Furthermore, the thickness h3 of the protective layer 11 can be greater than 10 microns, thereby ensuring the structural strength of the diffraction grating layer 12.

[0060] S202 , vapor-depositing at least two polarization modulation layers on the protective layer, and spin-coating photoresist.

[0061] For example, the vapor deposition methods in the embodiments of the present application include but are not limited to physical vapor deposition (PVD) and chemical vapor deposition (CVD).

[0062] The above-mentioned at least two polarization modulation layers may include a polarization modulation layer b1 located at the top and a polarization modulation layer b2 located at the bottom. Exemplarily, the deposition thickness of the polarization modulation layer b1 located at the top may be 900 nanometers to 1020 nanometers, and the deposition thickness of the polarization modulation layer b2 located at the bottom may be 150 nanometers to 420 nanometers.

[0063] S203 , performing at least two holographic exposures with exposure directions forming a preset angle with each other on the at least two polarization modulation layers subjected to the spin coating process, and then obtaining a polarization beam splitter through development and etching operations.

[0064] For example, if at least two polarization modulation layers include a polarization modulation layer b1 located at the top and a polarization modulation layer b2 located at the bottom, the two exposure directions can be at a preset angle of 90 degrees to each other. The advantage of this arrangement is that the grating structure morphology of the two polarization modulation layers is simple, which saves process procedures, and has a wide production tolerance, thereby ensuring product yield.

[0065] It should be noted that, for the description of the same contents in this embodiment as in other embodiments, reference can be made to the description in other embodiments and will not be repeated here.

[0066] The polarization beam splitter manufacturing method provided in an embodiment of the present application spatially modulates an incident light beam by disposing a diffraction grating layer on a protective layer. The grating period is 570 to 590 nanometers. That is, the diffraction grating layer can interact with the incident light field, changing the electromagnetic field transmission form of the incident light field on the surface of the diffraction grating layer to achieve polarization control. At the same time, at least two polarization modulation layers stacked in the diffraction grating layer can transmit the light beam. Thus, the hierarchical structure can spatially separate incident light beams of different polarization states at the transmission diffraction order. The structure is simple, significantly reduces the complexity of the optical system, and facilitates efficient integration.

[0067] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A polarization beam splitter, characterized in that: The polarization beam splitter (1) comprises: a protective layer (11); A diffraction grating layer (12) located on the protective layer (11), the diffraction grating layer (12) comprising optical units (121) arranged at equal intervals, the optical units (121) comprising at least two polarization modulation layers stacked in sequence along a transmission direction of an incident light beam, and a grating period Λ of the diffraction grating layer (12) being 570 nanometers to 590 nanometers.

2. The polarization beam splitter according to claim 1, wherein The at least two polarization modulation layers include a first polarization modulation layer (a1) and a second polarization modulation layer (a2), and the first polarization modulation layer (a1) and the second polarization modulation layer (a2) are both columnar structures.

3. The polarization beam splitter according to claim 2, wherein The column structure includes a cylinder, a prism or a frustum.

4. The polarization beam splitter according to claim 1, wherein The polarization modulation layer (b1) located at the top of the at least two polarization modulation layers is a tantalum pentoxide layer, and the polarization modulation layer (b2) located at the bottom is a magnesium fluoride layer.

5. The polarization beam splitter according to claim 4, wherein: The width ratio of the polarization modulation layer (b1) located at the top and the width ratio of the polarization modulation layer (b2) located at the bottom are both 0.5 to 0.

55.

6. The polarization beam splitter according to claim 4, wherein: The polarization modulation layer (b1) located on the top has a thickness of 900 nm to 1020 nm; And / or, the polarization modulation layer (b2) located at the bottom has a thickness of 150 nm to 420 nm.

7. The polarization beam splitter according to any one of claims 1 to 6, characterized in that: The thickness of the protective layer (11) is greater than 10 microns.

8. The polarization beam splitter according to any one of claims 1 to 6, wherein: The central wavelength λ of the incident light beam is 540 nm to 560 nm, and 9. An optical device, characterized in that: The optical device (2) comprises the polarization beam splitter (1) according to any one of claims 1 to 8.

10. The optical device according to claim 9, wherein The optical device (2) is a virtual reality display device, an augmented reality display device, or a mixed reality display device.

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