阅读说明：本技术 基于微纳半波片的振幅型光栅的制作方法 (Manufacturing method of amplitude type grating based on micro-nano half-wave plate ) 是由 李子乐 郑国兴 邓联贵 戴琦 付娆 邓娟 于 2019-09-24 设计创作，主要内容包括：本发明涉及一种基于微纳半波片的振幅型光栅的制作方法,属于微纳光学及衍射光学领域,该微纳半波片由多个纳米砖结构阵列构成,纳米砖结构阵列包括多个纳米砖结构单元,以偏振方向沿x轴或y轴的线偏振光垂直入射所述纳米砖结构阵列后,其透射光偏振方向会发生改变,透射光再经过一检偏方向与入射线偏振光方向平行的检偏器后,由马吕斯定律可知其振幅会发生变化,振幅变化量与微纳半波片转角相关,通过合理设计多个纳米砖结构阵列中的微纳半波片转角分布,可以得到振幅型光栅。本发明制得的振幅型光栅的振幅可连续调制,且只需一次光刻,加工容易,设计灵活。(The invention relates to a method for manufacturing an amplitude type grating based on a micro-nano half wave plate, which belongs to the field of micro-nano optics and diffraction optics, wherein the micro-nano half wave plate is composed of a plurality of nano brick structure arrays, each nano brick structure array comprises a plurality of nano brick structure units, the polarization direction of transmitted light can be changed after linearly polarized light along an x axis or a y axis in the polarization direction vertically enters the nano brick structure array, the amplitude of the transmitted light can be known to be changed by Malus law after the transmitted light passes through an analyzer parallel to the direction of the incident linearly polarized light in the polarization direction, the amplitude variation quantity is related to the rotation angle of the micro-nano half wave plate, and the amplitude type grating can be obtained by reasonably designing the rotation angle distribution of the micro-nano half wave plate in the plurality of nano brick structure arrays. The amplitude of the amplitude type grating manufactured by the invention can be continuously modulated, and only one-time photoetching is needed, so that the processing is easy, and the design is flexible.)

1. A manufacturing method of an amplitude type grating based on a micro-nano half-wave plate is characterized by comprising the following steps:

constructing a nano-brick structure unit, and optimizing to obtain the structure parameters of the nano-brick structure unit which is equivalent to a half-wave plate in function when the nano-brick structure unit is incident at a working wavelength, wherein the nano-brick structure unit comprises a transparent substrate and a nano-brick arranged on a working surface of the substrate, an x axis and a y axis are respectively set in directions parallel to two edges of the working surface to establish an xoy coordinate system, a long axis L and a short axis W are arranged on a surface parallel to the working surface on the nano-brick, and the steering angle of the nano-brick is the included angle theta between the long axis L and the x axis of the nano-brick;

constructing a nano-brick structure array, wherein the nano-brick structure array comprises a plurality of nano-brick structure units, linearly polarized light with the polarization direction along the x axis or the y axis vertically enters the nano-brick structure array, then passes through an analyzer with the polarization direction parallel to the incident linearly polarized light direction, the cosine relation between the amplitude variation of the incident linearly polarized light after passing through the nano-brick structure units and the analyzer and the twice nano-brick steering angle theta is obtained, then the nano-brick steering angle theta in each nano-brick structure unit is determined according to the amplitude modulation distribution required by the grating to be processed and the cosine relation between the obtained amplitude variation and the twice nano-brick steering angle theta, and the nano-bricks on each nano-brick structure unit in the nano-brick structure array are arranged according to the obtained nano-brick steering angle theta corresponding to each position, thereby obtaining an amplitude type grating.

2. The method for manufacturing the amplitude type grating based on the micro-nano half-wave plate according to claim 1, wherein the method for optimizing and obtaining the structural parameters of the nano-brick structural unit comprises the following steps: and when two linearly polarized light beams with mutually vertical polarization directions are simultaneously vertical to the working surface to enter, the two linearly polarized light beams have the same transmittance and the phase difference is equal to pi as an optimization target, and under the working wavelength, the structural parameters of the nano brick structural unit required by the target are obtained through electromagnetic simulation optimization.

3. The method for manufacturing an amplitude type grating based on a micro-nano half-wave plate according to claim 2, wherein the structural parameters of the nano-brick structural unit comprise the side length C of the working surface and the dimensions of the long axis L, the short axis W and the height H of the nano-brick.

4. The method for manufacturing an amplitude type grating based on a micro-nano half-wave plate according to claim 1, wherein the size of each nano-brick in the nano-brick structure array and the center interval of every two adjacent nano-bricks are the same.

5. The method for manufacturing an amplitude type grating based on a micro-nano half-wave plate according to claim 1, wherein the transparent substrate is made of fused silica glass material, and the nano-brick is made of dielectric material.

6. An amplitude type grating manufactured by the manufacturing method of the amplitude type grating based on the micro-nano half-wave plate according to any one of claims 1 to 5.

Technical Field

The invention relates to the technical field of micro-nano optics and diffraction optics, in particular to a method for manufacturing an amplitude type grating based on a micro-nano half-wave plate.

Background

Diffraction gratings that modulate the amplitude of incident light waves are called amplitude gratings, which are also called black and white gratings, and commonly used amplitude gratings include rectangular gratings and sinusoidal gratings. The rectangular grating is formed by carving a large number of slits on a transparent substrate, and amplitude modulation of light only has two states of full transmission and non-transmission. Accordingly, a grating in which the transmission coefficient varies as a sinusoidal function is called a sinusoidal grating, and since the intensity distribution function of the two-beam interference pattern has the form of a sinusoidal function, the transmission coefficient distribution of a negative film in which the two-beam interference fringes are recorded has the form of a sine after linear exposure, and such a negative film is a sinusoidal grating. In order to manufacture an amplitude type grating having a more complicated transmission coefficient distribution, it is necessary to construct a complicated interference light field and perform exposure. On the one hand, the resolution of the interference light field is limited by the diffraction limit, and not all the transmission coefficient distributions can construct the corresponding interference light field. On the other hand, a complex interference light field is constructed and exposed, and the method for constructing the amplitude type grating has the disadvantages of high processing difficulty, low cost and difficulty in batch replication. Therefore, the processing and application of the current complex amplitude type grating are greatly limited.

Disclosure of Invention

Based on the defects in the prior art, the invention aims to provide the method for manufacturing the amplitude type grating based on the micro-nano half-wave plate, the grating manufactured by the method can realize any transmission coefficient distribution, and has wide application prospect.

The scheme adopted by the invention for solving the technical problems is as follows:

a manufacturing method of an amplitude type grating based on a micro-nano half-wave plate comprises the following steps:

constructing a nano-brick structure unit, and optimizing to obtain the structure parameters of the nano-brick structure unit which is equivalent to a half-wave plate in function when the nano-brick structure unit is incident at a working wavelength, wherein the nano-brick structure unit comprises a transparent substrate and a nano-brick arranged on a working surface of the substrate, an x axis and a y axis are respectively set in directions parallel to two edges of the working surface to establish an xoy coordinate system, a long axis L and a short axis W are arranged on a surface parallel to the working surface on the nano-brick, and the steering angle of the nano-brick is the included angle theta between the long axis L and the x axis of the nano-brick;

constructing a nano-brick structure array, wherein the nano-brick structure array comprises a plurality of nano-brick structure units, linearly polarized light with the polarization direction along the x axis or the y axis vertically enters the nano-brick structure array, then passes through an analyzer with the polarization direction parallel to the incident linearly polarized light direction, the cosine relation between the amplitude variation of the incident linearly polarized light after passing through the nano-brick structure units and the analyzer and the twice nano-brick steering angle theta is obtained, then the nano-brick steering angle theta in each nano-brick structure unit is determined according to the amplitude modulation distribution required by the grating to be processed and the cosine relation between the obtained amplitude variation and the twice nano-brick steering angle theta, and the nano-bricks on each nano-brick structure unit in the nano-brick structure array are arranged according to the obtained nano-brick steering angle theta corresponding to each position, thereby obtaining an amplitude type grating.

Further, the method for optimizing and obtaining the structural parameters of the nano brick structural unit comprises the following steps: and when two linearly polarized light beams with mutually vertical polarization directions are simultaneously vertical to the working surface to enter, the two linearly polarized light beams have the same transmittance and the phase difference is equal to pi as an optimization target, and under the working wavelength, the structural parameters of the nano brick structural unit required by the target are obtained through electromagnetic simulation optimization.

Further, the structural parameters of the nano-brick structural unit comprise the side length C of the working face and the dimensions of the long axis L, the short axis W and the height H of the nano-brick.

Further, the size of each nano-brick in the nano-brick structure array and the center interval of every two adjacent nano-bricks are the same.

Further, the transparent substrate is made of fused silica glass material, and the nano-brick is made of dielectric material.

The invention also aims to provide the amplitude type grating prepared by the method for manufacturing the amplitude type grating based on the micro-nano half-wave plate.

The invention provides an amplitude type grating based on a micro-nano half-wave plate, which is composed of a plurality of nano brick structure arrays, and when linearly polarized light is incident, the polarization direction of transmitted light can be changed. When the transmitted light passes through an analyzer, the amplitude of the transmitted light can be known to change according to the Malus law, and the variable quantity is related to the rotation angle of the micro-nano half-wave plate. By reasonably designing the corner distribution of the micro-nano half-wave plate, the amplitude type grating can be realized. The invention relates to the following principle:

in the technical scheme of the invention, under a certain working wavelength, the nano-brick structure unit can be equivalent to a half-wave plate, namely the linearly polarized light with the polarization direction along the long axis of the nano-brick has the same transmittance as the linearly polarized light with the polarization direction along the short axis of the nano-brick, and the phase difference is pi. When the polarization direction of incident linearly polarized light is along the x-axis, the polarization adjustment function of each nano-brick structure unit in the nano-brick structure array to linearly polarized light can be illustrated by the following formula,

that is, when linearly polarized light with a polarization direction along the x-axis enters, the transmitted light is still linearly polarized light, but the included angle between the polarization direction and the x-axis is 2 theta.

On the basis of the technical scheme, when the transmitted light is analyzed and deflected by adopting the analyzer which is used for analyzing and deflecting along the x axis, the amplitude of the transmitted light is changed into

I.e., the transmitted light is again polarized along the x-axis with an amplitude of cos2 theta.

On the basis of the technical scheme, any amplitude modulation can be realized by changing the size of the steering angle theta of the nano brick, and the amplitude type grating can be constructed.

Compared with the prior art, the invention has at least the following beneficial effects:

1) the amplitude type grating provided by the invention has a continuous amplitude modulation function, can realize any transmittance distribution, and has flexible design and powerful function;

2) the sizes of the nanometer unit structures are all sub-wavelength levels, so the amplitude type grating designed by the invention has small volume, light weight and high integration, and is suitable for the development of miniaturization and micromation in the future;

3) the amplitude type grating is of a two-step plane structure, so that the processing and manufacturing, mass production and the like are simple, and the cost is saved.

Drawings

FIG. 1 is a schematic structural diagram of a nano-brick structural unit in an embodiment of the present invention;

FIG. 2 is a top view of a nano-brick structural unit in an embodiment of the invention;

FIG. 3 is a scanning chart of the transmittance of the long and short axes of the nano-brick structure unit in the embodiment of the present invention;

FIG. 4 is a phase scan of the long and short axes of the nano-brick structure units in an embodiment of the present invention;

FIG. 5 is an electron microscope image of an amplitude type grating according to an embodiment of the present invention.

Detailed Description

The following examples are provided to further illustrate the present invention for better understanding, but the present invention is not limited to the following examples.

In view of the problems existing in the prior art for manufacturing the amplitude type grating, the invention provides a method for manufacturing the amplitude type grating based on a micro-nano half-wave plate, which comprises the following steps:

constructing a nano brick structure unit, and optimizing to obtain the structure parameters of the nano brick structure unit which is equivalent to a half-wave plate in function when the nano brick structure unit is incident with a working wavelength, wherein the nano brick structure unit comprises a transparent substrate and a nano brick arranged on the working surface of the substrate, an x axis and a y axis are respectively set in the directions parallel to the two edges of the working surface to establish an xoy coordinate system, a long axis L and a short axis W are arranged on the surface parallel to the working surface on the nano brick, and the steering angle of the nano brick is the included angle theta between the long axis L and the x axis of the nano brick;

the method comprises the steps of constructing a nano-brick structure array, wherein the nano-brick structure array comprises a plurality of nano-brick structure units, linearly polarized light in the polarization direction along the x axis or the y axis vertically enters the nano-brick structure array, then passes through an analyzer in which the polarization direction is parallel to the incident linearly polarized light direction, the amplitude variation of the linearly polarized light after passing through each nano-brick structure unit and the analyzer has a cosine relation with twice nano-brick steering angles theta, then determining the nano-brick steering angles theta in each nano-brick structure unit according to the amplitude modulation distribution required by the grating to be processed and the cosine relation between the obtained amplitude variation and the twice nano-brick steering angles theta, and arranging the nano-bricks on each nano-brick structure unit in the nano-brick structure array according to the obtained nano-brick steering angles theta corresponding to each position, so as to obtain the amplitude type grating.

In this embodiment, the material used for the nano-brick is titanium dioxide, but may also be other dielectric materials, such as silicon; the substrate is made of fused quartz glass material, and the nano brick is deposited on the working surface of the substrate. The individual nano-brick building blocks are shown in fig. 1, and their top views are shown in fig. 2. The working surface of the transparent substrate of the nano brick structural unit is square, and the side length of the working surface is C; l is the long axis dimension of the nano brick, W is the short axis dimension of the nano brick, H is the height of the nano brick, the dimensions are all sub-wavelength levels, and theta is the orientation angle of the nano brick. The amplitude type grating comprises a nano-brick structure array, the nano-brick structure array comprises a plurality of nano-brick structure units, and the size and the central interval of each adjacent nano-brick in the nano-brick structure array are the same. In order to enable the nano unit to work equivalently as a half-wave plate, when two beams of linearly polarized light with mutually vertical polarization directions vertically enter a working face, the size of the nano brick structure unit is obtained by optimization according to the transmittance and the phase of the two beams of incident light, namely the nano brick structure unit is obtained by optimization according to the condition that the linearly polarized light along the long axis of the nano brick in the polarization direction is the same as the linearly polarized light along the short axis of the nano brick in the polarization direction and the phase difference is pi.

Specifically, taking the working wavelength λ of 480nm as an example, modeling and simulating by using electromagnetic simulation software, when the orientation angle of the nano-brick is 0, taking x-linearly polarized light with the polarization direction along the x axis and y-linearly polarized light with the polarization direction along the y axis to be incident perpendicular to the working surface at the same time, scanning the structural parameters of the nano-brick structural unit under the working wavelength, including L, W, H, C, taking the optimization objects that the two beams have the same polarized light transmittance and the phase difference is equal to pi as the optimization objects, and obtaining the scanning results as shown in fig. 3 and 4. Under the condition of the working wavelength, the transmittances of x linearly polarized light and y linearly polarized light are both about 90%, the phase difference of the two linearly polarized light beams is equal to pi, and the structural parameters of the nano brick structural unit are as follows: l-210 nm, W-100 nm, H-600 nm, C-400 nm. Under the structural parameters of the optimized nano-brick structural unit, the nano-brick structural unit can be equivalent to a half-wave plate.

When the polarization direction of incident linearly polarized light is along the x-axis, the polarization adjusting function of each nanoblock structure unit in the nano-unit array to linearly polarized light can be illustrated by the following formula,

that is, when linearly polarized light having a polarization direction along the x axis is incident, the transmitted light is still linearly polarized light, and the angle between the polarization direction and the x axis is 2 θ.

When transmitted light is analyzed and deflected by an analyzer along the x-axis in the analyzing and deflecting direction, the amplitude of the transmitted light is changed into

I.e., the transmitted light is again polarized along the x-axis with an amplitude of cos2 theta.

According to the principle, the cosine relation between the amplitude variation and the double nano-brick steering angle theta is obtained, so that arbitrary amplitude modulation can be realized by changing the size of the nano-brick steering angle theta, and the amplitude type grating can be constructed. Specifically, the nano-brick steering angle theta in each nano-brick structure unit is determined according to the amplitude modulation distribution required by the grating to be processed and the cosine relationship cos2 theta between the amplitude variation and twice the nano-brick steering angle theta, and then the nano-bricks on each nano-brick structure unit in the nano-brick structure array are arranged according to the obtained micro-nano brick steering angles theta corresponding to the positions, so that the amplitude type grating is obtained. In the present embodiment, when a grating having an amplitude distribution in the form of cosine is constructed, the nanoblock linearly increases toward the angle, and a picture taken by an amplitude type grating electron microscope at this time is as shown in fig. 5.

In other embodiments, the operating wavelength and the amplitude-type grating transmittance distribution may be set as needed to obtain a desired amplitude-type grating.

While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.