Preparation method of grating with continuously-changed diffraction efficiency
阅读说明：本技术 一种衍射效率连续变化的光栅的制备方法 (Preparation method of grating with continuously-changed diffraction efficiency ) 是由 *** 罗豪 于 2020-07-14 设计创作，主要内容包括：本发明公开了一种衍射效率连续变化的光栅的制备方法：采用两束光谱波段互相不重叠的第一束光和第二束光,第一束光进行干涉后形成干涉光,第二束光形成空间上有连续光强变化的光；将干涉光与空间上有连续光强变化的光同时照射到光敏材料上,得到衍射效率连续变化的光栅；光敏材料为光固化材料,干涉光使光敏材料固化,空间上有连续光强变化的光抑制光敏材料固化；或光敏材料为光致折射率变化的材料。本发明提供的制备方法直接通过对光敏材料曝光得到,主要针对现有的基于波导光栅耦合器的光学系统的出射光束存在均匀性较差的缺点,可以获得光强均匀的分布的出射光束,从而有效提升光学系统的成像能力和信息传输能力等性能。(The invention discloses a method for preparing a grating with continuously-changed diffraction efficiency, which comprises the following steps: two beams of first light and second light with mutually non-overlapping spectral bands are adopted, the first light forms interference light after interference, and the second light forms light with continuous light intensity change on space; simultaneously irradiating interference light and light with continuous light intensity change on the space onto a photosensitive material to obtain a grating with continuously changed diffraction efficiency; the photosensitive material is a photocuring material, the interference light enables the photosensitive material to be cured, and the light with continuous light intensity change spatially inhibits the curing of the photosensitive material; or the photosensitive material is a material that induces a change in refractive index. The preparation method provided by the invention is directly obtained by exposing the photosensitive material, mainly aims at the defect of poor uniformity of the emergent light beam of the existing optical system based on the waveguide grating coupler, and can obtain the emergent light beam with uniform light intensity distribution, thereby effectively improving the performances of the optical system such as imaging capability, information transmission capability and the like.)
1. A method for preparing a grating with continuously-changed diffraction efficiency is characterized by comprising the following steps: two beams of light with mutually non-overlapping spectral bands are adopted, namely a first beam of light and a second beam of light; the first beam of light forms interference light after interference, and the second beam of light forms light with continuous light intensity change on space; simultaneously irradiating interference light and light with continuous light intensity change on the space onto a photosensitive material to obtain a grating with continuously changed diffraction efficiency; the photosensitive material is a light curing material, the interference light enables the photosensitive material to be cured, and the light with continuous light intensity change spatially inhibits the curing of the photosensitive material.
2. The method for manufacturing a grating with continuously changing diffraction efficiency as claimed in claim 1, wherein the first beam of light is emitted from a laser, and then passes through a beam splitter to obtain two beams of light, the two beams of light form a certain included angle after being reflected by a reflector, and then pass through a beam expanding lens, a filtering pinhole and a collimating lens respectively to interfere with each other to form interference light, and the interference light is irradiated on a photosensitive material; or the first beam of light is emitted by the laser, passes through the beam expanding lens, the filtering pinhole and the collimating lens, and then passes through the wedge-shaped flat plate to form bright and dark interference fringes to irradiate on the photosensitive material.
3. The method of claim 1, wherein the first beam of light is emitted from a point light source, and then passes through a fresnel double prism to form bright and dark interference fringes to be irradiated on the photosensitive material.
4. The method of claim 1, wherein the second beam of light is emitted from a laser and passes through a beam expander lens, a filter pinhole, and a collimating lens to obtain a beam expander beam with a gaussian distribution; the expanded beam passes through a shaping lens to obtain a beam with uniformly distributed light intensity; the light beam with uniform light intensity distribution is superposed with the neutral filter with continuously changing transmittance to obtain light with spatially continuous light intensity change.
5. The method of claim 1, wherein the second beam of light is emitted from a laser, passes through a beam expanding lens, a filter pinhole, and a collimating lens to obtain a gaussian expanded beam, and then passes through a free-form shaping lens to form a spatially continuous beam of light intensity.
6. A method for preparing a grating with continuously-changed diffraction efficiency is characterized by comprising the following steps: two beams of light with mutually non-overlapping spectral bands are adopted, namely a first beam of light and a second beam of light; the first beam of light forms interference light after interference, and the second beam of light forms light with continuous light intensity change on space; simultaneously irradiating interference light and light with continuous light intensity change on the space onto a photosensitive material to obtain a grating with continuously changed diffraction efficiency; wherein the photosensitive material is a material with a photoinduced refractive index change.
7. The method for manufacturing a grating with continuously changing diffraction efficiency as claimed in claim 6, wherein the first beam of light is emitted from a laser, and then passes through a beam splitter to obtain two beams of light, the two beams of light form a certain included angle after being reflected by a reflector, and then mutually interfere to form interference light after passing through a beam expanding lens, a filtering pinhole and a collimating lens respectively, and the interference light is irradiated on a photosensitive material; or the first beam of light is emitted by the laser, passes through the beam expanding lens, the filtering pinhole and the collimating lens, and then passes through the wedge-shaped flat plate to form bright and dark interference fringes to irradiate on the photosensitive material.
8. The method of claim 6, wherein the first beam of light is emitted from a point light source, and then passes through a Fresnel double prism to form bright and dark interference fringes to be irradiated on the photosensitive material.
9. The method of claim 6, wherein the second beam of light is emitted from a laser and passes through a beam expander lens, a filter pinhole, and a collimating lens to obtain a beam expander beam with Gaussian distribution; the expanded beam passes through a shaping lens to obtain a beam with uniformly distributed light intensity; the light beam with uniform light intensity distribution is superposed with the neutral filter with continuously changing transmittance to obtain light with spatially continuous light intensity change.
10. The method of claim 6, wherein the second beam of light is emitted from a laser and passes through a beam expander lens, a filter pinhole, and a collimating lens to obtain a beam expander beam with Gaussian distribution; and then a light beam with continuous light intensity change on the space is formed by the shaping lens of the free-form surface.
Technical Field
The invention relates to the field of waveguide optical diffraction elements, in particular to a method for preparing a grating with continuously-changed diffraction efficiency.
Technical Field
A grating refers to a diffractive element having a periodic variation in an optical parameter (e.g., transmittance, refractive index, etc.) or spatial structure distribution. The preparation of the grating is an important link of grating research, and the selected optical materials comprise the following categories: glass material systems, semiconductor material systems, inorganic crystalline material systems, organic material systems, and the like. The fabrication of gratings has been studied around the process of these materials. The grating can be divided into a surface etching grating and a bulk grating. At present, a surface etching grating modulates light beams through a surface periodic space microstructure, and is mainly prepared by using a photoresist grating mask, an ion etching process or a reactive ion etching process and the like. The volume grating is a permanent grating prepared by a photosensitive method, and the refractive index of the grating is periodically distributed. Such gratings therefore achieve modulation of the refractive index primarily through design and non-structural changes in the material. The existing method for manufacturing the grating has complex process flow and higher cost.
The optical waveguide is a device capable of binding the optical wave in the medium with the size of optical wavelength magnitude for long-distance non-radiative loss transmission, and after the grating is introduced into the optical waveguide structure, the formed waveguide grating coupler can realize the input and output coupling of the light in the waveguide by using the waveguide grating structure, so the waveguide grating coupler is one of the most important components in the optical waveguide. Waveguide grating couplers are widely applied in the fields of optical interconnection, integrated optical devices, optical fiber communication and the like, and particularly in recent years, with the rapid development of augmented reality technology, particularly the deep research on augmented reality display technology, the application field of waveguide grating couplers is further expanded.
The waveguide grating coupling device is often used as a light beam in-out coupling element of an optical system, and a light beam is deflected by an input coupler and enters an optical waveguide, propagates to an exit region through total internal reflection in the optical waveguide, and then is deflected again by an output coupler and exits from the optical waveguide. The properties of the waveguide-grating coupler are therefore very important to the performance of the overall optical system.
However, the existing optical system based on the waveguide grating coupler has the disadvantage of poor uniformity of the outgoing light beam, and the main reason is that the transmitted light beam is reflected for multiple times by the waveguide and is sequentially diffracted by the grating in the output process, the reflection times of the transmitted light beam in the coupled light grating area are different, so that the light intensity loss is different, and the diffraction efficiency of the currently used waveguide grating is fixed and unchanged, so the incoming and outgoing light intensity is sequentially weakened, which can cause the outgoing light beam to flicker and even discontinuity of images in the imaging process, or affect the accuracy of light-carrying information and other negative effects. In order to obtain uniform uninterrupted light beam output, the diffraction efficiency distribution of the output grating needs to be optimized, i.e. the continuous change of the diffraction efficiency of the grating is realized.
Disclosure of Invention
The invention aims to provide a preparation method of a grating with continuously-changed diffraction efficiency, which can solve the defect of poor uniformity of an emergent light beam of an optical system based on a waveguide grating coupler and is simple.
A preparation method of a grating with continuously-changed diffraction efficiency comprises the following steps: two beams of light with mutually non-overlapping spectral bands are adopted, namely a first beam of light and a second beam of light; the first beam of light forms interference light after interference, and the second beam of light forms light with continuous light intensity change on space; simultaneously irradiating interference light and light with continuous light intensity change on the space onto a photosensitive material to obtain a grating with continuously changed diffraction efficiency; the photosensitive material is a light curing material, the interference light enables the photosensitive material to be cured, and the light with continuous light intensity change spatially inhibits the curing of the photosensitive material.
The first beam of light is emitted by the laser, and then passes through the beam splitter to obtain two beams of light, the two beams of light form a certain included angle after being reflected by the reflector, and then mutually interfere to form interference light after respectively passing through the beam expanding lens, the filtering pinhole and the collimating lens, and the interference light irradiates on the photosensitive material.
Or the first beam of light is emitted by the laser, passes through the beam expanding lens, the filtering pinhole and the collimating lens, and then passes through the wedge-shaped flat plate to form bright and dark interference fringes to irradiate on the photosensitive material.
Wherein, the included angle formed after the two beams of light are reflected by the reflector does not exceed 40 degrees.
Or the first beam of light is emitted from the point light source and forms bright and dark interference fringes after passing through the Fresnel double prism to irradiate on the photosensitive material.
After the second beam of light is emitted by the laser, the second beam of light passes through the beam expanding lens, the filtering pinhole and the collimating lens to obtain a beam expanding beam in Gaussian distribution; the expanded beam passes through a shaping lens to obtain a beam with uniformly distributed light intensity; the light beam with uniform light intensity distribution is superposed with the neutral filter with continuously changing transmittance to obtain light with spatially continuous light intensity change.
Or the second beam of light is emitted by the laser, passes through the beam expanding lens, the filtering pinhole and the collimating lens to obtain a Gaussian-distributed beam expanding beam and then directly passes through the free-form surface shaping lens to form a beam with continuous light intensity change in space.
In the present invention, the wavelengths of the first beam of light and the second beam of light are related to a photosensitive material, the photosensitive material includes a light curing agent sensitive to interference light (the first beam of light) and a light inhibitor sensitive to light intensity changes (the second beam of light). Wherein, the photosensitive material is selected according to actual needs.
The grating with continuously changed diffraction efficiency obtained by the preparation method is a rectangular grating with continuously changed groove depth. The continuous variation in groove depth further causes a continuous variation in the diffraction efficiency of the grating.
The invention also provides another preparation method of the grating with continuously changed diffraction efficiency, which comprises the following steps: two beams of light with mutually non-overlapping spectral bands are adopted, namely a first beam of light and a second beam of light; the first beam of light forms interference light after interference, and the second beam of light forms light with continuous light intensity change on space; simultaneously irradiating interference light and light with continuous light intensity change on the space onto a photosensitive material to obtain a grating with continuously changed diffraction efficiency; wherein the photosensitive material is a material with a photoinduced refractive index change.
The change in the internal photo-refractive index of the photo-refractive index changeable material is proportional to the exposure light intensity.
The first beam of light is emitted by the laser, and then passes through the beam splitter to obtain two beams of light, the two beams of light form a certain included angle after being reflected by the reflector, and then mutually interfere to form interference light after respectively passing through the beam expanding lens, the filtering pinhole and the collimating lens, and the interference light irradiates on the photosensitive material.
Or the first beam of light is emitted by the laser, passes through the beam expanding lens, the filtering pinhole and the collimating lens, and then passes through the wedge-shaped flat plate to form bright and dark interference fringes to irradiate on the photosensitive material.
Wherein, the included angle formed after the two beams of light are reflected by the reflector does not exceed 40 degrees.
Or the first beam of light is emitted from the point light source and forms bright and dark interference fringes after passing through the Fresnel double prism to irradiate on the photosensitive material.
After the second beam of light is emitted by the laser, the second beam of light passes through the beam expanding lens, the filtering pinhole and the collimating lens to obtain a beam expanding beam in Gaussian distribution; the expanded beam passes through a shaping lens to obtain a beam with uniformly distributed light intensity; the light beam with uniform light intensity distribution is superposed with the neutral filter with continuously changing transmittance to obtain light with spatially continuous light intensity change.
Or the second beam of light is emitted by the laser, passes through the beam expanding lens, the filtering pinhole and the collimating lens to obtain a Gaussian-distributed beam expanding beam and then directly passes through the free-form surface shaping lens to form a beam with continuous light intensity change in space.
The grating with continuously changed diffraction efficiency obtained by the preparation method is a volume grating with continuously changed internal refractive index distribution. The continuous change in the internal refractive index profile further causes a continuous change in the diffraction efficiency of the grating.
Aiming at the defect of poor uniformity of emergent light beams of the existing optical system based on the waveguide grating coupler, the invention provides a preparation method of a grating with continuously-changed diffraction efficiency. Compared with the traditional method for manufacturing the grating, the method has simpler process flow and lower cost.
Drawings
FIG. 1 is a schematic diagram of the structure of a grating prepared in example 1;
FIG. 2 is a rectangular grating with continuously varying diffraction efficiency obtained in example 1;
FIG. 3 is a graph showing the relationship between diffraction efficiency of a rectangular grating and groove depth in example 1;
FIG. 4 is a schematic diagram showing the structure of a grating prepared in example 2;
FIG. 5 shows a volume Bragg grating in which the diffraction efficiency is continuously varied in example 2;
FIG. 6 is a graph showing the relationship between the diffraction efficiency and the refractive index modulation degree of a Bragg grating for preparing a grating body in example 2;
FIG. 7 is a schematic structural diagram of a grating according to the present invention;
FIG. 8 is a schematic diagram showing the structure of a grating prepared in example 3;
FIG. 9 is a schematic diagram showing the structure of a grating prepared in example 4;
the device comprises a laser with the wavelength of a 1, a laser with the wavelength of b, a
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and examples.
- 上一篇：一种医用注射器针头装配设备
- 下一篇：带通滤光片及其制备方法