CN109164536B - Intelligent optical power distribution device based on super surface material - Google Patents

Abstract

The invention provides an intelligent optical power distribution device based on metasurface material, which is characterized by comprising: the nano-brick units are arranged and can focus the orthogonal linearly polarized light incident along the long and short axis directions of the nano-brick units respectively. A metasurface array structure for optical power distribution to different positions, wherein the nanobrick unit is composed of a dielectric substrate and nanobricks formed on the dielectric substrate, and both the dielectric substrate and the nanobricks have subwavelength dimensions. The intelligent optical power distribution device provided by the present invention utilizes the polarization-independent properties of the transmission phase metasurface material to perform phase manipulation of the orthogonal light waves along the long and short axes of the nanobricks, respectively, and separate the orthogonal light waves along the long and short axes of the nanobricks. Focusing to different positions for efficient optical power distribution.

Description

Intelligent optical power distribution device based on metasurface materials

technical field

The invention belongs to the field of micro-nano optics, in particular to an intelligent optical power distribution device based on metasurface materials.

technical background

The optical power divider is a passive optical device that divides the optical signal into multiple outputs. The current optical power splitter has a coupling type splitter and a branch type splitter. A coupling splitter is a device that couples and redistributes optical signals in a special coupling area. The spectroscopic ratio of this device is difficult to precisely control, and the fabrication process is complicated and the cost is high. The bifurcated optical path directly divides the optical signal into multiple output devices. The splitting ratio is controlled by adjusting the branch angle, and it is difficult to realize real-time splitting ratio regulation for a certain fixed branched optical path device. Therefore, new method breakthroughs and innovations are urgently needed.

SUMMARY OF THE INVENTION

The present invention is carried out to solve the above problems, and the purpose is to provide an intelligent optical power distribution device based on metasurface materials, which utilizes the polarization-independent properties of the transmission phase metasurface materials to detect orthogonal light waves along the long and short axes of the nanobricks. Phase manipulation is performed separately to focus the orthogonal light waves along the long and short axes of the nanobricks to different positions, thereby achieving efficient optical power distribution.

In order to achieve the above object, the present invention adopts the following scheme:

The invention provides an intelligent optical power distribution device based on metasurface material, which is characterized in that: it is formed by arranging nano-brick units, and can focus the orthogonal linearly polarized light waves incident along the long and short axis directions of the nano-brick units respectively to A metasurface array structure for optical power distribution at different positions, wherein the nanobrick unit is composed of a dielectric substrate and nanobricks formed on the dielectric substrate, and both the dielectric substrate and the nanobricks have subwavelength dimensions.

Further, the intelligent optical power distribution device based on the metasurface material provided by the present invention may also have the following characteristics: in the metasurface array structure, the length and width of the nanobricks are different, and the lengths and widths of the nanobricks are different in size, through the parallel to the x-axis direction and the y-axis direction. Nanobricks of different lengths control the phase and transmittance of the incident light respectively, so that the linearly polarized light in the x-direction and the linearly polarized light in the y-direction are focused to different positions after passing through the nanobrick array, thereby realizing optical power distribution.

Further, the intelligent optical power distribution device based on the metasurface material provided by the present invention may also have the following characteristics: the structural parameters of the nano-brick unit are obtained by the following methods:

为优化指标；对各相位量化值组

以透射效率最高、且

与

差值绝对值小于预设值作为优化目标，满足该优化目标的结构参数即为

对应的结构参数；

和

分别表示硅纳米砖单元x轴方向和y轴方向的位相值。Let the x-axis direction and the y-axis direction be the directions parallel to the long and short axes of the nanobricks, respectively, and the efficiency of the transmitted linearly polarized light parallel to the x-axis direction and the linearly polarized light parallel to the y-axis direction and Phase Value Group for Nanobrick Cells

is an optimization index; for each phase quantization value group

with the highest transmission efficiency, and

and

The absolute value of the difference is less than the preset value as the optimization objective, and the structural parameters that satisfy the optimization objective are

Corresponding structural parameters;

and

represent the phase values in the x-axis and y-axis directions of the silicon nanobrick unit, respectively.

The above-mentioned metasurface array structure is an array formed by arranging silicon nano-brick units, and the silicon nano-brick units are composed of a dielectric substrate and silicon nano-bricks etched on the dielectric substrate. In the silicon nanobrick unit, both the dielectric substrate and the silicon nanobrick are rectangular parallelepipeds, the length, width and height of the dielectric substrate and the silicon nanobrick are both subwavelength scales, and the working surface of the dielectric substrate is a square. The surfaces of the dielectric substrate and the silicon nano-bricks etched thereon are respectively parallel, and the line connecting the center points of the dielectric substrate and the silicon nano-bricks etched thereon is perpendicular to the dielectric substrate.

The direction of the long and short axes of the metasurface array structure is the direction corresponding to the long side and the short side of the cuboid nanobrick unit, respectively. In the metasurface array structure, all dielectric substrates have the same length, width and height; all silicon nanobricks have the same height, but different lengths and widths, which should be designed according to the phase requirements. Due to such a structure, the metasurface array structure has polarization-independent properties, and the phase and transmittance of linearly polarized light parallel to the x-axis direction are controlled by the length of the long-axis direction of the silicon nanobricks (x-direction). The length of the short-axis direction (y direction) controls the phase and transmittance of the linearly polarized light parallel to the y-axis direction, so that the linearly polarized light in the x-direction and the linearly polarized light in the y-direction can be focused on the silicon nanobrick array respectively. Different positions to achieve light splitting.

The design method of the above-mentioned metasurface array structure includes:

(1) Establish the working surface coordinate system of the silicon nanobrick unit, and the x-axis direction and the y-axis direction are respectively parallel to the two sets of sides of the working surface of the dielectric substrate;

分别表示x轴方向和y轴方向的相位量化值，

i、j相等或不相等；(2) Determine the quantization phase sampling level N, and construct the phase quantization value group

represent the phase quantization values in the x-axis direction and the y-axis direction, respectively,

i, j are equal or unequal;

(3) The structural parameters of the silicon nanobrick unit are optimized by electromagnetic simulation method. The structural parameters include the length Lx parallel to the x-axis direction and the y-axis direction of the silicon nanobrick, the height H of the Ly silicon nanobrick and the side length of the working surface of the dielectric substrate. C;

以透射效率最高、且

与

差值绝对值小于预设值作为优化目标，满足该优化目标的结构参数即为

对应的结构参数。The phase corresponding to the structural parameters of each nanobrick unit

with the highest transmission efficiency, and

and

The absolute value of the difference is less than the preset value as the optimization objective, and the structural parameters that satisfy the optimization objective are

corresponding structural parameters.

(4) Obtaining structural parameters corresponding to each phase based on the optimization result of step (3), and arranging each unit structure to a corresponding position to obtain a metasurface array structure.

The role and effect of the invention

(1) The present invention can realize phase modulation in the range of 2π only by changing the size of the silicon nano-brick unit, the process is simple, and has high stability and reliability.

(2) The present invention adopts the polarization-independent silicon nano-brick unit to realize the control of the linearly polarized light in the x-direction and the linearly-polarized light in the y-direction, so as to focus on different positions in different directions and realize the division of labor. Further, by means of a polarizer, the optical components of the incident light in the long and short axis directions can be changed, thereby realizing real-time, arbitrary, and accurate optical power distribution.

(3) The present invention can change the light components of the incident light in the direction of the long and short axes only by means of the polarizer, so as to realize the regulation of any light splitting ratio, and the operation is simple and easy to realize. The principle of changing the light component with the help of a polarizer is that light in any polarization direction can be decomposed into a combination of two mutually orthogonal linearly polarized lights. After passing through the polarizer, it becomes linearly polarized light along the direction of the polarizer. The linearly polarized light can be further decomposed along the long and short axes of the nanobricks, so as to realize the regulation of incident light energy, and only the direction of the polarizer needs to be changed. Then real-time, arbitrary and precise control can be realized.

(4) The intelligent optical power distribution device provided by the present invention has low cost and can be mass-produced; the unit size is small, which is convenient for integration, and can be widely used in optical fiber communication, sensing and other fields.

Description of drawings

1 is a schematic diagram of a partial structure of a metasurface array structure designed in an embodiment of the present invention;

2 is a schematic structural diagram of a silicon nanobrick unit in an embodiment of the present invention;

Fig. 3 is the result graph of the change of the phase and transmittance of the transmitted light with the size of the nano-brick in the embodiment of the present invention, wherein (a) is the result of the change of the phase in the X direction with the length Lx and the width Ly of the nano-brick, and (b) is the X direction The results of the transmittance changing with the nanobrick length Lx and width Ly, (c) is the result of the Y-direction phase changing with the nanobrick length Lx and width Ly, (d) is the Y-direction transmittance changing with the nanobrick length Lx and width Ly. Ly change result;

FIG. 4 is a working principle diagram of an optical power distribution device in an embodiment of the present invention.

Detailed ways

The specific embodiments of the metasurface material-based intelligent optical power distribution device involved in the present invention will be described in detail below with reference to the accompanying drawings.

<Example>

As shown in FIGS. 1 and 2 , the intelligent optical power distribution device 10 based on a metasurface material provided in this embodiment is a metasurface array structure formed by arranging a plurality of silicon nanobrick units 11 . The silicon nanobrick unit 11 is composed of a dielectric substrate 11a and a silicon nanobrick 11b etched thereon. Both the dielectric substrate 11a and the silicon nanobricks 11b are rectangular parallelepipeds, the length, width and height of the dielectric substrate 11a and the silicon nanobricks 11b are both subwavelength scales, and the working surface of the dielectric substrate 11a is square. The surfaces of the dielectric substrate 11a and the silicon nanobricks 11b etched thereon are respectively parallel, and the line connecting the center points of the dielectric substrate 11a and the silicon nanobricks 11b etched thereon is perpendicular to the dielectric substrate 11a. All the dielectric substrates 11a have the same length, width and height; all the silicon nanobricks 11b have the same height, but different lengths and widths.

Due to such a structure, the metasurface array structure has polarization-independent properties, and the phase and transmittance of linearly polarized light parallel to the x-axis direction are controlled by the length of the silicon nanobrick 11b in the long-axis direction (x-direction). The length of the short-axis direction of the brick 11b (y direction) controls the phase and transmittance of the linearly polarized light parallel to the y-axis direction, so that the linearly polarized light in the x-direction and the linearly polarized light in the y-direction can pass through the silicon nanobrick 11b array. They are focused to different positions to realize optical power distribution.

The specific method involved in the intelligent optical power distribution device 10 includes the following steps:

The first step: determine the main wavelength according to the actual use, that is, the working wavelength. In this embodiment, the dominant wavelength is 658 nm. The silicon nanobrick is made of crystalline silicon material, and the dielectric substrate is made of fused silica glass material.

Step 2: Phase quantization is 4 steps. Determine the phase quantization values, which are 0°, 90°, 180°, and 270°, respectively. This embodiment can construct 16 groups of phase quantization value groups

为优化指标，扫描单元结构尺寸C、纳米砖长宽Lx、Ly和高度H，以期获得满足优化目标的最佳参数。对各相位量化值组

以透射效率最高、且

与

的差值绝对值小于预设值(15°)为优化目标，满足该优化目标的结构参数即

对应的结构参数；The third step: for the wavelength and the number of quantized steps, use linearly polarized light parallel to the x-axis direction and linearly polarized light parallel to the y-axis direction to enter the working surface of the silicon nanobrick unit vertically at the same time, so that the transmitted light is parallel to the x-axis direction. The efficiency of linearly polarized light and linearly polarized light parallel to the y-axis direction, and the phase values in the x-axis and y-axis directions

In order to optimize the index, the cell structure size C, the length and width Lx, Ly and height H of the nanobricks were scanned to obtain the best parameters to meet the optimization goal. For each phase quantization value group

with the highest transmission efficiency, and

and

The absolute value of the difference is less than the preset value (15°) as the optimization goal, and the structural parameters that meet the optimization goal are

Corresponding structural parameters;

After optimization, C=250nm, H=310nm, and different Lx and Ly correspond to different transmittance and phase retardation.

As shown in Figure 3, by analyzing the scanning results, taking the highest transmission efficiency and the smallest absolute value of the difference from the target phase group as the optimization goal, the nanobrick size that satisfies the 4-step distribution is obtained (marked by the circle in Figure 3).

Table 1 below provides the corresponding _Lx and _Ly values for each set of phase values. Among them, XT and YT represent the transmission efficiency of the linearly polarized light parallel to the x-axis direction and the linearly polarized light parallel to the y-axis direction, respectively, and X-phase and Y-phase represent the phase values in the x-axis direction and the y-axis direction, respectively. . It can be seen from Table 1 that the optimized silicon nanobrick unit can obtain high transmittance and consistency while ensuring the phase value.

Table 1 Corresponding table of 4-step phase value and transmission efficiency corresponding to Lx and Ly

Step 4: Based on the following phase distribution calculation formula, obtain the phase value of any point on the nano-brick array, then quantify the continuous phase in 4 steps, and then obtain the structural parameters corresponding to each phase based on the optimization results of the third step, and quantify each cell. When the structures are arranged in corresponding positions, the metasurface array structure shown in Fig. 3 is obtained.

where f is the focal length, and x and y are the coordinates of the nanobricks on the metasurface array. θ _x , θ _y are the off-axis angles of the focus after the linearly polarized light parallel to the x-axis and the linearly polarized light parallel to the y-axis pass through the nanobrick array. λ is the wavelength.

As shown in FIG. 4 , the working principle of the intelligent optical power distribution device 10 provided in this embodiment is as follows: when the linearly polarized light along the x direction is incident, the light splitting ratio of the intelligent optical power distribution device 10 is 1:0. When linearly polarized light in the y-direction is incident, the light splitting ratio of the intelligent optical power distribution device 10 is 0:1. Light of any polarization state can be decomposed into a combination of two mutually orthogonal linearly polarized lights. Therefore, by adjusting the rotation direction of the polarizer, an arbitrary splitting ratio M:N can be achieved for light of any polarization state.

The above embodiments are merely examples to illustrate the technical solutions of the present invention. The metasurface material-based intelligent optical power distribution device involved in the present invention is not limited only to the content described in the above embodiments, but is subject to the scope defined by the claims. Any modifications or additions or equivalent substitutions made by those skilled in the art of the present invention on the basis of this embodiment are within the scope of protection claimed in the claims of the present invention.

Claims (2)

1. An intelligent optical power distribution device based on a metamaterial, comprising:

is a super-surface array structure which is formed by arranging nano-brick units and can focus orthogonal linear polarized light waves incident along the long and short axis directions of the nano-brick units to different positions respectively for optical power distribution,

wherein the nano brick unit is composed of a medium substrate and a nano brick formed on the medium substrate, the length and the width of the nano brick are different, the medium substrate and the nano brick are both in sub-wavelength size, the nano brick is made of a crystalline silicon material, the medium substrate is made of a fused quartz glass material,

the light component of the incident light in the long and short axis directions can be changed by the polarizer, thereby realizing real-time, random and accurate light power distribution,

the structural parameters of the nano brick units are obtained by adopting the following method:

setting the x-axis direction and the y-axis direction as the directions parallel to the long axis and the short axis of the nano brick respectively, vertically irradiating the linearly polarized light parallel to the x-axis direction and the linearly polarized light parallel to the y-axis direction simultaneously to the working surface of the silicon nano brick unit, and setting the efficiency of the transmitted linearly polarized light parallel to the x-axis direction and the linearly polarized light parallel to the y-axis direction and the phase value group of the silicon nano brick unit

In order to optimize the indexes,

for each set of phase quantized values

With the highest transmission efficiency and

and

absolute value of difference less thanThe preset value is taken as an optimization target, and the structural parameters meeting the optimization target are

The corresponding structural parameters are set to be in a certain range,

the above-mentioned

And

respectively representing the phase values of the silicon nano brick unit in the x-axis direction and the y-axis direction,

sixteen groups of phase quantization value groups are constructed by adopting sixteen nano bricks

2. The intelligent optical power distribution device of claim 1, wherein:

in the super-surface array structure, the phase and transmittance of incident light are respectively controlled by the nano bricks with different lengths parallel to the x-axis direction and the y-axis direction, so that linearly polarized light in the x direction and linearly polarized light in the y direction are respectively focused to different positions after passing through the nano brick array, and light splitting is realized.

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