Exposure device with adjustable interference angle without other optical components, exposure method and preparation method of reflective volume grating

Abstract

The invention relates to the technical field of optical element manufacturing, in particular to an exposure device with an adjustable interference angle without other optical elements, an exposure method and a preparation method of a reflective volume grating. The exposure device comprises a laser source, a reflector, a beam expanding system, a collimating lens, an optical rotating table and PTR glass, wherein the PTR glass is arranged on the optical rotating table; wherein laser emitted by the laser source passes through the reflector, is subjected to light spot beam expansion through the beam expansion system, and is subjected to light beam collimation through the collimating lens, and then the light beam enters the PTR glass body and is interfered in the PTR glass body to form interference fringes; by rotating the optical rotating table, a light beam is incident into the PTR glass body at different angles, and interference fringes of different periods are formed by changing the interference angle. The interference angle is changed by adjusting the light incident angle, the reflective volume grating with different wavelengths is prepared, interference can be automatically formed without depending on redundant optical components, and meanwhile the reflective volume grating has the advantages of being low in cost, simple in structure, easy to operate, beneficial to large-scale production and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of optical element manufacturing, and in particular to an exposure device and an exposure method with adjustable interference angle without other optical components, and a preparation method of a reflective volume grating. Background Art

[0002] Volume grating holographic exposure technology is a grating produced using holographic photography technology. It uses the principle of optical coherence superposition to form a series of uniform interference fringes through the interference of two light waves, and then forms a holographic image on the photosensitive material, thereby producing a grating latent image with high line groove density and large line width. The latent image is then processed through development technology to complete the structure preparation.

[0003] From the grating equation 2dsinθ=λ, we can know that when the exposure wavelength λ is known, the interference angle θ is the most critical for grating preparation, because its sine value is directly inversely proportional to the grating period d. The interference angle of traditional exposure systems is generally fixed and cannot be adjusted, or it relies on certain components for adjustment.

[0004] The current exposure methods mainly include double-beam interferometry, immersion exposure, and prism exposure. The double-beam interferometry method requires dual light sources or splitting a single light source. Its optical path is large, complex, and unstable, and has certain limitations on the exposure angle. The immersion exposure method requires building an optical path in a refractive index matching liquid and adjusting the light field. The actual operation is difficult and the long-term use of the matching liquid cannot be guaranteed. The prism exposure method requires adding a suitable refractive index matching liquid between the prism and the PTR glass, and coating a reflective film on the back of the PTR glass or adding a high-reflectivity mirror. In addition, these exposure devices have the following disadvantages in the actual production of volume gratings: 1. Volume grating products have many wavelengths, and traditional exposure devices need to dismantle and rebuild the exposure light path according to the wavelengths of different products to obtain corresponding gratings of different equal periods; 2. The refractive index of the photothermorefractive glass, the raw material of the volume grating, has slight fluctuations, and it is necessary to fine-tune the interference angle to obtain the corresponding wavelength stability; 3. Traditional interference angle continuously adjustable exposure mostly relies on other optical elements, such as mirrors and prisms, which are complex to build and costly, and other auxiliary materials are required for preparation in the later stage, such as mirrors, photothermorefractive glass coatings, matching liquids, etc.

[0005] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an exposure device, an exposure method and a method for preparing a reflective volume grating with adjustable interference angle without the need for other optical components, aiming to solve the problem that the existing exposure devices with continuously adjustable interference angle mostly rely on other optical elements, are complex to build, costly, and require other auxiliary materials for preparation in the later stage.

[0007] The technical solution of the present invention is as follows:

[0008] A first aspect of the present invention provides an exposure device with adjustable interference angle without other optical components, wherein the device comprises a laser source, a reflector, a beam expansion system, a collimating lens, an optical rotating table, and a PTR glass, wherein the PTR glass is arranged on the optical rotating table;

[0009] The laser emitted by the laser source passes through the reflector and then the beam is expanded by the beam expansion system. After the beam is collimated by the collimating lens, the beam is incident on the PTR glass body, and interference occurs inside the PTR glass to form interference fringes.

[0010] By rotating the optical rotating table, the light beam is incident on the PTR glass at different angles, and interference fringes of different periods are formed by changing the interference angle.

[0011] Optionally, a wedge angle α of the PTR glass is ≠90°.

[0012] Optionally, the exposure device further comprises an optical baffle, and the optical baffle is used to block stray light after the light beam is collimated.

[0013] A second aspect of the present invention provides an exposure method for preparing reflective volume gratings of different wavelengths, wherein the exposure is performed using the exposure device with adjustable interference angle without other optical components as described in the present invention, and the exposure method comprises the steps of:

[0014] According to the exposure wavelength λ 曝 and the target wavelength λ of the reflective volume grating 使 , calculate the rotation angle θ of the optical rotating table;

[0015] The optical rotating stage is rotated by angle θ, and the laser source emits a wavelength of λ 曝 The laser passes through the reflector and then expands the spot through the beam expansion system. After the beam is collimated by the collimating lens, the beam is incident on the PTR glass body, where interference occurs. After a predetermined dose of beam exposure, the exposure is stopped.

[0016] Optionally, the exposure wavelength λ 曝 and the target wavelength λ of the reflective volume grating 使 , the steps of calculating the rotation angle θ of the optical rotating table specifically include:

[0017] The surfaces a and b of the PTR glass to be exposed are polished to form a light-transmitting surface and a reflective surface. The PTR glass is 曝 The refractive index is n1, and the target wavelength λ of the reflective volume grating is 使 The refractive index under is n2;

[0018] The polished PTR glass is placed on an optical rotating table and the laser source with a wavelength of λ 曝 The laser beam passes through the reflector and then expands the beam through the beam expansion system. After the beam is collimated by the collimating lens, the beam is perpendicular to the surface a. At this time, the rotation angle θ of the optical rotating stage is 0°. According to the grating equation Calculate the rotation angle θ of the optical rotating stage.

[0019] A third aspect of the present invention provides a method for preparing a reflective volume grating of different wavelengths, which includes an exposure step, and the exposure step is performed using the exposure method described in the present invention.

[0020] Beneficial effects: The present invention can change the α angle of the PTR glass and the incident angle of light during exposure through processing to change the interference angle to form interference fringes of different periods, thereby preparing reflective volume gratings of different wavelengths. It does not rely on redundant optical components and can form interference by itself. At the same time, it has low cost, simple structure, easy operation, and is conducive to large-scale production. It has good application prospects in the fields of laser beam combining, spatial filtering, laser locking, line width narrowing, etc.

[0021] The reflective volume grating preparation method provided by the present invention does not need to add additional optical matching liquid and optical elements on the PTR glass, has a simple structure, and is convenient for adjusting the optical path, and can realize the preparation of reflective volume gratings of different wavelengths. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the internal exposure light path of the PTR glass of the present invention.

[0023] Figure 2 The diagram is a light path diagram of an exposure device with adjustable interference angle that does not require other optical components according to the present invention. DETAILED DESCRIPTION

[0024] The present invention provides an exposure device, an exposure method and a method for preparing a reflective volume grating with an adjustable interference angle without other optical components. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Please combine Figure 1-Figure 2 As shown, an embodiment of the present invention provides an exposure device with adjustable interference angle without other optical components, which includes a laser source 1, a reflector 2, a beam expansion system 3, a collimating lens 4, an optical rotating table 5, a PTR glass 6, and an optical baffle 7, wherein the PTR glass 6 is arranged on the optical rotating table 5;

[0026] The laser emitted by the laser source 1 passes through the reflector 2 and then the beam is expanded by the beam expansion system 3, and the beam is collimated by the collimating lens 4 and directly irradiated on the PTR glass 6. When the light beam passes through the surface a of the PTR glass 6, it is incident on the body of the PTR glass 6 at an angle θ (the incident angle θ is equal to the angle between the incident light beam and the normal of the surface a of the PTR glass). The light beam satisfies total reflection on the surface b of the PTR glass 6, and the reflected light and the incident light interfere with each other inside the PTR glass 6 to form interference fringes.

[0027] By rotating the optical rotating table 5, the light beam is incident on the PTR glass body at different angles, and interference fringes of different periods are formed by changing the interference angle, so as to prepare reflective volume gratings of different wavelengths.

[0028] The optical baffle 7 is used to block excess stray light.

[0029] The wedge angle α of the PTR glass is ≠90°.

[0030] The PTR glass surface a refers to the light incident surface during exposure.

[0031] The PTR glass surface b refers to the total internal reflection formed by surface b when light enters the PTR glass body through surface a during exposure.

[0032] The wedge angle α of the PTR glass refers to the angle between surface a and surface b, and the angle is ≠90°.

[0033] The embodiment of the present invention can adjust the α angle of the PTR glass and the light incident angle to change the interference angle to form interference fringes of different periods, thereby preparing a reflective volume grating with different wavelengths. It does not rely on redundant optical components and can form interference by itself. At the same time, it has low cost, simple structure, easy operation, and is conducive to large-scale production. It has good application prospects in the fields of laser beam combining, spatial filtering, laser locking, line width narrowing, etc.

[0034] An embodiment of the present invention provides an exposure method for preparing reflective volume gratings of different wavelengths, wherein the exposure is performed using an exposure device with adjustable interference angle without other optical components as described in the embodiment of the present invention. The exposure method comprises the steps of:

[0035] According to the exposure wavelength λ 曝 and the target wavelength λ of the reflective volume grating 使 , calculate the rotation angle θ of the optical rotating table;

[0036] The optical rotating stage is rotated by angle θ, and the laser source emits a wavelength of λ 曝The laser passes through the reflector and then expands the spot through the beam expansion system. After the beam is collimated by the collimating lens, the beam is incident on the PTR glass body, where interference occurs. After a predetermined dose of beam exposure, the exposure is stopped.

[0037] An embodiment of the present invention provides a method for preparing a reflective volume grating of different wavelengths, wherein the method comprises an exposure step, and the exposure step is performed using the exposure method described in the embodiment of the present invention.

[0038] The reflective volume grating preparation method provided by the embodiment of the present invention does not need to add additional optical matching liquid and optical elements on the PTR glass, has a simple structure, and is convenient for adjusting the optical path, and can realize the preparation of reflective volume gratings of different wavelengths.

[0039] Specifically, the target wavelength is λ 使 The reflective volume grating, where the exposure process is as follows:

[0040] A beam of parallel ultraviolet light (emitted by laser source 1) is provided for exposing the PTR glass 6, and the exposure wavelength is λ 曝 ;

[0041] The surfaces a and b of the PTR glass 6 to be exposed are polished to form a light-transmitting surface and a reflective surface. The PTR glass 6 is 曝 The refractive index under the reflective volume grating is n1, and the target wavelength (also called the use wavelength or working wavelength) λ 使 The refractive index under is n2;

[0042] Place the polished PTR glass 6 on the optical rotating table 5 and build the Figure 2 The exposure device shown in the figure has a wavelength of λ emitted by the laser source 1. 曝 The laser beam passes through the reflector 2 and then expands the beam through the beam expansion system 3. After the beam is collimated by the collimating lens 4, the beam is perpendicular to the surface a. At this time, the rotation angle θ of the optical rotating table 5 is 0°. According to the grating equation Calculate the rotation angle θ of the optical rotating table 5;

[0043] The optical rotating platform 5 is rotated by an angle θ, and the wavelength of the laser light emitted by the laser source 1 is λ 曝 The laser passes through the reflector 2 and then expands the spot through the beam expansion system 3. After the beam is collimated by the collimating lens 4, the beam is incident on the surface a of the PTR glass 6, forming interference in the body of the PTR glass 6. After a certain dose of ultraviolet exposure, the exposure is stopped.

[0044] The present invention is further described in detail below through specific examples.

[0045] Example 1

[0046] Prepare a reflective volume grating with a target wavelength of 520 nm, where the exposure process is as follows:

[0047] The wavelength of the parallel UV light used for exposure is λ 曝 =325nm;

[0048] Select a PTR glass 6 with a wedge angle of 45°, polish the surfaces a and b of the PTR glass 6 to be exposed to form a light-transmitting surface and a reflective surface, the refractive index of the PTR glass 6 at an exposure wavelength of 325 nm is n1=1.53, and the refractive index at a target wavelength of 520 nm for the reflective volume grating is n2=1.506;

[0049] Place the PTR glass 6 on the optical rotating table 5 and build Figure 2 The exposure device shown in the figure has a wavelength of λ emitted by the laser source 1. 曝 The laser beam passes through the reflector 2 and then expands the beam through the beam expansion system 3. After the beam is collimated by the collimating lens 4, the beam is perpendicular to the surface a. At this time, the rotation angle θ of the optical rotating table 5 is 0°. According to the grating equation The rotation angle θ of the optical rotating stage 5 is calculated to be 37.966°;

[0050] The optical rotating platform 5 is rotated 37.966°, and the wavelength of the laser source 1 is λ 曝 The laser passes through the reflector 2 and then expands the spot through the beam expansion system 3. After the beam is collimated by the collimating lens 4, the beam is incident on the surface a of the PTR glass 6, forming interference in the body of the PTR glass 6. After a certain dose of ultraviolet exposure, the exposure is stopped.

[0051] Example 2

[0052] Prepare a reflective volume grating with a target wavelength of 405 nm, where the exposure process is as follows:

[0053] The wavelength of the parallel UV light used for exposure is λ 曝 =325nm;

[0054] Select a PTR glass with a wedge angle of 45°, polish the surfaces a and b of the PTR glass to be exposed to form a light-transmitting surface and a reflective surface, and coat the surface b of the PTR glass with a UV high-reflective film. The refractive index of the PTR glass is n1=1.53 at an exposure wavelength of 325nm, and the refractive index is n2=1.5158 at a target wavelength of 405nm for the reflective volume grating.

[0055] Place the PTR glass 6 on the optical rotating table 5 and build Figure 2 The exposure device shown in the figure has a wavelength of λ emitted by the laser source 1. 曝The laser beam passes through the reflector 2 and then expands the beam through the beam expansion system 3. After the beam is collimated by the collimating lens 4, the beam is perpendicular to the surface a. At this time, the rotation angle θ of the optical rotating stage is 0°. According to the grating equation The rotation angle θ of the optical rotating stage 5 is calculated to be 1.2578°;

[0056] The optical rotating platform 5 is rotated by 1.2578°, and the wavelength of the laser source 1 is λ 曝 The laser passes through the reflector 2 and then expands the spot through the beam expansion system 3. After the beam is collimated by the collimating lens 4, the beam is incident on the surface a of the PTR glass 6, forming interference in the body of the PTR glass 6. After a certain dose of ultraviolet exposure, the exposure is stopped.

[0057] In summary, the present invention provides an exposure device, an exposure method and a method for preparing a reflective volume grating with adjustable interference angle without the need for other optical components. The present invention can adjust the α angle of the PTR glass and the incident angle of light to change the interference angle to form interference fringes of different periods, thereby preparing reflective volume gratings of different wavelengths. It does not rely on redundant optical components and can form interference by itself. At the same time, it has low cost, simple structure, easy operation, and is conducive to large-scale production. It has good application prospects in the fields of laser beam combining, spatial filtering, laser locking, line width narrowing, etc. The reflective volume grating preparation method provided by the present invention does not require the addition of additional optical matching liquid and optical elements to the PTR glass, has a simple structure, and is convenient for adjusting the optical path, and can realize the preparation of reflective volume gratings of different wavelengths.

[0058] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An exposure device with adjustable interference angle without other optical components, characterized in that: It includes a laser source, a reflector, a beam expansion system, a collimating lens, an optical rotating table, and a PTR glass, wherein the PTR glass is arranged on the optical rotating table; The laser emitted by the laser source passes through the reflector and then the beam is expanded by the beam expansion system. After the beam is collimated by the collimating lens, the beam is incident on the PTR glass body, and interference occurs inside the PTR glass to form interference fringes. By rotating the optical rotating table, the light beam is incident on the PTR glass at different angles, and interference fringes of different periods are formed by changing the interference angle.

2. The exposure device with adjustable interference angle without other optical components according to claim 1, characterized in that: The wedge angle α of the PTR glass is ≠90°.

3. The exposure device with adjustable interference angle without other optical components according to claim 1, characterized in that: The exposure device also includes an optical baffle, which is used to block stray light after the light beam is collimated.

4. An exposure method for preparing reflective volume gratings of different wavelengths, characterized in that: Exposure is performed using the exposure device with adjustable interference angle without other optical components as described in any one of claims 1 to 3, the exposure method comprising the steps of: According to the exposure wavelength λ 曝 and the target wavelength λ of the reflective volume grating 使 , calculate the rotation angle θ of the optical rotating table; The optical rotating stage is rotated by angle θ, and the laser source emits a wavelength of λ 曝 The laser passes through the reflector and then expands the spot through the beam expansion system. After the beam is collimated by the collimating lens, the beam is incident on the PTR glass body, where interference occurs. After a predetermined dose of beam exposure, the exposure is stopped.

5. The exposure method for preparing reflective volume gratings of different wavelengths according to claim 4, characterized in that: According to the exposure wavelength λ 曝 and the target wavelength λ of the reflective volume grating 使 , the steps of calculating the rotation angle θ of the optical rotating table specifically include: The surfaces a and b of the PTR glass to be exposed are polished to form a light-transmitting surface and a reflective surface. The PTR glass is 曝 The refractive index is n1, and the target wavelength λ of the reflective volume grating is 使 The refractive index under is n2; The polished PTR glass is placed on an optical rotating table and the laser source with a wavelength of λ 曝 The laser beam passes through the reflector and then expands the beam through the beam expansion system. After the beam is collimated by the collimating lens, the beam is perpendicular to the surface a. At this time, the rotation angle θ of the optical rotating stage is 0°. According to the grating equation Calculate the rotation angle θ of the optical rotating stage.

6. A method for preparing reflective volume gratings of different wavelengths, characterized in that: The method comprises an exposure step, wherein the exposure step is performed by the exposure method according to any one of claims 4 to 5.

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