阅读说明：本技术 一种基于超表面阵列结构实现迂回相位编码复用的方法 (Method for realizing circuitous phase coding multiplexing based on super-surface array structure ) 是由 郑国兴 付娆 李子乐 单欣 李仲阳 于 2019-10-30 设计创作，主要内容包括：本发明公开了一种基于超表面阵列结构实现迂回相位编码复用的方法,该方法包括以下步骤：步骤1、优化设计可等效为微型起偏器的纳米砖单元结构；步骤2、纳米砖单元结构对应的透过率编码；步骤3、设计抽样单元实现复振幅调制；步骤4、复振幅全息复用设计；步骤5、生成透过率编码信息,求出包含四种方向角信息的方向角矩阵；步骤6、将纳米砖单元结构等间隔排列,构成超表面阵列结构。本发明提供的迂回相位编码复用设计方法简单、设计灵活、易于操作,可以实现复振幅全息,并且通过改变入射线偏振光的偏振状态可以产生两个完全不同的全息片,实现复振幅全息复用；超表面阵列结构的结构简单、体积小、重量轻、结构紧凑,具有极大的产业化前景。(The invention discloses a method for realizing circuitous phase coding multiplexing based on a super-surface array structure, which comprises the following steps: step 1, optimally designing a nano brick unit structure which can be equivalent to a micro polarizer; step 2, the transmittance codes corresponding to the nano brick unit structures; step 3, designing a sampling unit to realize complex amplitude modulation; step 4, designing complex amplitude holographic multiplexing; step 5, generating transmittance coding information, and obtaining a direction angle matrix containing four kinds of direction angle information; and 6, arranging the nano brick unit structures at equal intervals to form a super-surface array structure. The roundabout phase encoding multiplexing design method provided by the invention is simple, flexible in design and easy to operate, can realize complex amplitude holography, and can generate two completely different holographic sheets by changing the polarization state of incident linearly polarized light so as to realize complex amplitude holography multiplexing; the super-surface array structure has the advantages of simple structure, small volume, light weight and compact structure, and has great industrialization prospect.)

1. A method for realizing roundabout phase code multiplexing based on a super-surface array structure is characterized by comprising the following steps:

step 1, determining a working wavelength, and optimizing the size parameters of a nano brick unit structure through electromagnetic simulation software, so that when linearly polarized light in any polarization state under the working wavelength is normally incident to the nano brick unit structure, the linearly polarized light component transmittance vibrating along the major axis direction of the nano brick unit structure is minimum, and the linearly polarized light component transmittance vibrating along the minor axis direction of the nano brick unit structure is maximum;

2, selecting four nano brick unit structures with different direction angles, and changing the corresponding transmittance of the nano brick unit structures by changing the polarization state of incident linear polarized light to form four codes;

step 3, the sampling unit comprises t multiplied by t nano brick unit structures, the number of the nano brick unit structures of the transmission part of the sampling unit is changed to control the transmittance of the sampling unit, namely, the light transmission area of the clear aperture is changed to code the amplitude, and meanwhile, the positions of the center of the clear aperture and the center of the sampling unit are changed to code the phase, so that complex amplitude holography is realized;

step 4, designing two holographic films: holographic plate H₁And hologram H₂Each of the M × N sampling units includes a complex amplitude distribution satisfying a complex amplitude distribution function; encoding the two holograms according to step 3 to generate two 0-1 transmittance matrices T of (M x T) x (N x T) elements₁And matrix T₂；

Step 5, matrix T₁And matrix T₂The element positions of (a) are in one-to-one correspondence, and the matrix T is formed₁And matrix T₂Simultaneously generating transmission rate coding information, and correspondingly obtaining a direction angle matrix only containing information corresponding to four direction angles according to the coding information in the step 2;

and 6, arranging the nano brick unit structures with the consistent size and the direction angles arranged according to the direction angle matrix at equal intervals in the x direction and the y direction to form the super surface array structure.

2. The method for realizing detour phase encoding multiplexing based on the super-surface array structure as claimed in claim 1, wherein the size parameters of the nano-brick unit structure in step 1 include: the length L, the width W, the height H and the side length C of the unit structure substrate of the nano brick.

3. The method for realizing roundabout phase coding multiplexing based on the super-surface array structure according to claim 1, wherein the orientation angles Φ of the nano-brick unit structures in the step 2 are 22.5 °, 67.5 °, 112.5 ° and 157.5 °, and the incident light is linearly polarized light with θ ═ 0 ° and θ ═ 45 °; the transmittances corresponding to the nano-brick unit structures at the four direction angles are respectively 0, 1 and 1, and when the polarization state of incident linearly polarized light is changed, the transmittances corresponding to the nano-brick unit structures are changed to form four codes of 00, 10, 11 and 01.

4. The method for realizing detour phase encoding multiplexing based on the super surface array structure as claimed in claim 1, wherein the complex amplitude distribution function adopted in step 4 is:

holographic plate H₁The complex amplitude distribution of the (m, n) -th sampling unit in (a) is:

holographic plate H₂The complex amplitude distribution of the (m, n) -th sampling unit in (a) is:

wherein A is_mn1And A_mn2For holographic disk H₁And hologram H₂Normalized amplitude of (i.e. 0 ≦ A)_mn1≤1，0≤A_mn2≤1；

5. The method for realizing detour phase encoding multiplexing based on the super-surface array structure of claim 1, wherein the super-surface array structure in step 6 is composed of a substrate and a nano-brick array etched on the substrate, and the nano-brick array is composed of (M × t) × (N × t) nano-brick unit structures.

6. The method for realizing roundabout phase coding multiplexing based on the super-surface array structure as claimed in claim 5, wherein the substrate material is silicon dioxide, and the nano-brick unit structure material is silver.

7. The method for realizing detour phase encoding multiplexing based on the super-surface array structure as claimed in claim 1, wherein the operating wavelength in step 1 is 633 nm.

8. The method for realizing roundabout phase encoding multiplexing based on the super-surface array structure as claimed in claim 7, wherein when the operating wavelength is 633nm, the length of the nano-brick is 160nm, the width of the nano-brick is 80nm, the height of the nano-brick is 70nm, and the side length of the unit structure substrate is 300 nm.

Technical Field

The invention relates to the technical field of micro-nano optics, in particular to a method for realizing circuitous phase coding multiplexing based on a super-surface array structure.

Background

Computer holography has been widely used in the fields of three-dimensional holographic imaging and optical data storage, etc. to record amplitude and phase information of a target object by approximation and digitization, and then reproduce the recorded complex amplitude information and reproduce the wave front. Most current computer-generated holography devices only provide amplitude or phase modulation, however, theoretically, in order to perfectly reproduce the light wave profile, the amplitude and the phase of the light wave need to be modulated at the same time, that is, the complex amplitude of the light wave needs to be modulated.

The super-surface is a plane optical element with a sub-wavelength scale structure, which is designed and manufactured manually, can flexibly and effectively regulate and control a light wave electromagnetic field in the sub-wavelength scale, is widely applied to wavefront engineering, and the holography is promoted to make a great progress under the promotion of super-surface research.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for realizing roundabout phase code multiplexing based on a super-surface array structure by combining the super-surface array structure aiming at the defects in the prior art, and the roundabout phase code multiplexing can be realized only by changing the polarization state of incident linearly polarized light.

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

the invention provides a method for realizing circuitous phase coding multiplexing based on a super-surface array structure, which comprises the following steps:

step 1, determining a working wavelength, and optimizing the size parameters of a nano brick unit structure through electromagnetic simulation software, so that when linearly polarized light in any polarization state under the working wavelength is normally incident to the nano brick unit structure, the linearly polarized light component transmittance vibrating along the major axis direction of the nano brick unit structure is minimum, and the linearly polarized light component transmittance vibrating along the minor axis direction of the nano brick unit structure is maximum;

2, selecting four nano brick unit structures with different direction angles, and changing the corresponding transmittance of the nano brick unit structures by changing the polarization state of incident linear polarized light to form four codes;

step 3, the sampling unit comprises t multiplied by t nano brick unit structures, the number of the nano brick unit structures of the transmission part of the sampling unit is changed to control the transmittance of the sampling unit, namely, the light transmission area of the clear aperture is changed to code the amplitude, and meanwhile, the positions of the center of the clear aperture and the center of the sampling unit are changed to code the phase, so that complex amplitude holography is realized;

step 4, designing two holographic films: holographic plate H₁And hologram H₂Each of the M × N sampling units includes a complex amplitude distribution satisfying a complex amplitude distribution function; encoding the two holograms according to step 3 to generate two 0-1 transmittance matrices T of (M x T) x (N x T) elements₁And matrix T₂；

Step 5, matrix T₁And matrix T₂The element positions of (a) are in one-to-one correspondence, and the matrix T is formed₁And matrix T₂Simultaneously generating transmission rate coding information, and correspondingly obtaining a direction angle matrix only containing information corresponding to four direction angles according to the coding information in the step 2;

and 6, arranging the nano brick unit structures with the consistent size and the direction angles arranged according to the direction angle matrix at equal intervals in the x direction and the y direction to form the super surface array structure.

Further, the dimensional parameters of the nano-brick unit structure in step 1 of the present invention include: the length L, the width W, the height H and the side length C of the unit structure substrate of the nano brick.

Further, the orientation angles Φ of the nano-brick unit structures in step 2 of the present invention are 22.5 °, 67.5 °, 112.5 ° and 157.5 °, and the incident light is linearly polarized light with θ ═ 0 ° and θ ═ 45 °; the transmittances corresponding to the nano-brick unit structures at the four direction angles are respectively 0, 1 and 1, and when the polarization state of incident linearly polarized light is changed, the transmittances corresponding to the nano-brick unit structures are changed to form four codes of 00, 10, 11 and 01.

Further, the complex amplitude distribution function adopted in step 4 of the present invention is:

holographic plate H₁The (m, n) -th sampling unit of (1)The complex amplitude distribution of (a) is:

holographic plate H₂The complex amplitude distribution of the (m, n) -th sampling unit in (a) is:

wherein A is_mn1And A_mn2For holographic disk H₁And hologram H₂Normalized amplitude of (i.e. 0 ≦ A)_mn1≤1，0≤A_mn2≤1；

And

for holographic disk H₁And hologram H₂The phase of (c).

Further, in step 6 of the present invention, the super-surface array structure is composed of a substrate and a nano-brick array etched on the substrate, and the nano-brick array is composed of (M × t) × (N × t) nano-brick unit structures.

Furthermore, the substrate material of the invention is silicon dioxide, and the nano brick unit structure material is silver.

Furthermore, the working wavelength in step 1 of the present invention is 633 nm.

Furthermore, when the working wavelength of the invention is 633nm, the length of the nano brick is 160nm, the width of the nano brick is 80nm, the height of the nano brick is 70nm, and the side length of the unit structure substrate is 300 nm.

The invention has the following beneficial effects: the method for realizing roundabout phase encoding multiplexing based on the super-surface array structure can realize complex amplitude holographic multiplexing only by changing the polarization state of incident linearly polarized light, and has the following advantages:

(1) the roundabout phase encoding multiplexing design method provided by the invention is simple, flexible in design and easy to operate, not only can realize complex amplitude holography, but also can generate two completely different holographic sheets by changing the polarization state of incident linearly polarized light so as to realize complex amplitude holography multiplexing;

(2) the super surface material (i.e. super surface array structure) has simple structure, small volume, light weight and compact structure, the related super surface manufacturing process is mature and simple, and can be copied and produced in large scale and at low cost, thereby having great industrialization prospect.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a schematic diagram of a direction angle of a nano-brick unit structure in a method for realizing roundabout phase coding multiplexing based on a super-surface array structure according to an embodiment of the present invention;

fig. 2 is a schematic size parameter diagram of a nano-brick unit structure in a method for implementing roundabout phase encoding multiplexing based on a super-surface array structure according to an embodiment of the present invention;

fig. 3 shows reflection and transmission efficiencies of a nano-brick unit structure designed in a method for implementing roundabout phase encoding multiplexing based on a super-surface array structure according to an embodiment of the present invention for linearly polarized light with two orthogonal polarization states vibrating in the major axis direction and the minor axis direction, respectively;

fig. 4 is a table of transmittance coding information corresponding to direction angles Φ of 22.5 °, 67.5 °, 112.5 °, and 157.5 ° when incident light is linearly polarized light with θ being 0 ° and θ being 45 ° in a method for implementing detour phase coding multiplexing based on a super-surface array structure according to an embodiment of the present invention;

FIG. 5 is a schematic diagram illustrating a principle of phase modulation implemented by a holographic sampling unit in a method for implementing roundabout phase encoding multiplexing based on a super-surface array structure according to an embodiment of the present invention;

fig. 6 is a schematic diagram illustrating a principle that a hologram sampling unit implements complex amplitude modulation in a method for implementing detour phase encoding multiplexing based on a super-surface array structure according to an embodiment of the present invention;

fig. 7 is an encoding process of implementing complex amplitude multiplexing by any sampling unit in a hologram in a method for implementing roundabout phase encoding multiplexing based on a super-surface array structure according to an embodiment of the present invention;

fig. 8 is a schematic diagram of a super-surface array structure formed by arranging four kinds of nano-brick unit structures with consistent size and direction angles of 22.5 °, 67.5 °, 112.5 °, and 157.5 ° at equal intervals in x and y directions in a method for realizing bypass phase coding multiplexing based on the super-surface array structure according to an embodiment of the present invention;

wherein, 1-nano brick unit structure and 2-substrate.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment provides a method for realizing roundabout phase coding multiplexing based on a super-surface array structure, which is characterized in that the transmittance of a sampling unit is controlled by changing the number of nano brick unit structures of a transmission part of the sampling unit, namely, the light transmission area of a clear aperture is changed to code amplitude, and the positions of the center of the clear aperture and the center of the sampling unit are changed to code phase, so that complex amplitude holography is realized. In addition, under the condition that the super-surface array structure is fixed, the complex amplitude distribution function of the holographic plate can be changed by adjusting the polarization state of incident linearly polarized light, so that complex amplitude holographic multiplexing is realized.

The method for realizing circuitous phase coding multiplexing based on the super surface array structure mainly comprises the following steps:

step 1, optimally designing a nano brick unit structure which can be equivalent to a micro polarizer. Determining the working wavelength, and optimizing the size parameters of the nano brick unit structure through electromagnetic simulation software, so that when linearly polarized light in any polarization state under the working wavelength is normally incident to the nano brick unit structure, the linearly polarized light component transmittance vibrating along the major axis direction of the nano brick unit structure is minimum, and the linearly polarized light component transmittance vibrating along the minor axis direction of the nano brick unit structure is maximum;

and 2, coding the transmittance corresponding to the nano brick unit structure. Selecting four nano brick unit structures with phi of 22.5 degrees, 67.5 degrees, 112.5 degrees and 157.5 degrees and different direction angles, wherein when incident light is linearly polarized light with theta of 0 degree, the transmittance corresponding to the nano brick unit structures with the four direction angles is 0, 1 and 0 respectively; when the incident light is linearly polarized light with theta being 45 degrees, the transmittances corresponding to the nano-brick unit structures of the four direction angles are respectively 0, 1 and 1, namely when the polarization state of the incident linearly polarized light is changed, the transmittances corresponding to the nano-brick unit structures are also changed, and four codes of 00, 10, 11 and 01 can be formed;

and 3, designing a sampling unit to realize complex amplitude modulation. The sampling unit comprises t multiplied by t nano brick unit structures, the transmittance of the sampling unit is controlled by changing the number of the nano brick unit structures of the transmission part (the transmittance is 1) of the sampling unit, namely, the light transmission area of the clear aperture is changed to code the amplitude, and meanwhile, the positions of the center of the clear aperture and the center of the sampling unit are changed to code the phase, so that complex amplitude holography is realized;

and 4, designing complex amplitude holographic multiplexing. Suppose two holograms H₁And H₂Each containing M x N sampling units, wherein the complex amplitude distribution of the (M, N) th sampling unit is

And

h is to be₁And H₂Generating two 0-1 transmittance matrixes T of (M x T) x (N x T) elements according to the step 3 coding₁And T₂；

Step 5, T₁And T₂The element positions of (A) are in one-to-one correspondence, and T is set₁And T₂Generating transmission rate coding information by matrix simultaneous, and correspondingly obtaining a direction angle matrix phi only containing four kinds of direction angle information of 22.5 degrees, 67.5 degrees, 112.5 degrees and 157.5 degrees according to the coding information in the step 2;

and 6, arranging the nano brick unit structures with consistent (M x t) x (N x t) sizes and direction angles arranged according to the direction angle matrix phi at equal intervals in the x and y directions to form the super-surface array structure.

The present invention is further described below.

1. The optimized design can be equivalent to a nano brick unit structure of a miniature polarizer.

The following description will be given taking the nano-brick unit structure as a rectangular parallelepiped. The length, width and height of the nano brick unit structure are all sub-wavelength.

As shown in fig. 1, an xoy rectangular coordinate system is established, the long side direction of the nano-brick unit structure 1 represents a long axis, the short side direction represents a short axis, and Φ is an included angle between the long axis and the x axis of the nano-brick unit structure 1, i.e., a direction angle (Φ is 0 ° -180 °) of the nano-brick unit structure 1, as shown in fig. 1.

Due to the difference in the long and short axis dimensions of the nano-tile unit structure 1, the electromagnetic response in both directions will also be different. The dimension parameters of the nano-brick unit structure, including the height H, length L, width W and unit structure base side length C of the nano-brick unit structure 1 (i.e. equivalent to dividing the substrate 2 into a plurality of unit structure bases), are optimized by electromagnetic simulation software, as shown in fig. 2. When linearly polarized light in any polarization state under working wavelength is normally incident to the nano brick unit structure 1, a group of size parameters with the smallest linearly polarized light component transmittance vibrating along the major axis direction of the nano brick unit structure 1 and the largest linearly polarized light component transmittance vibrating along the minor axis direction of the nano brick unit structure 1, namely the optimized size parameters of the nano brick unit structure 1, are obtained.

Because the linearly polarized light in any polarization state can be decomposed into two orthogonally polarized linearly polarized light, when the linearly polarized light in any polarization state is normally incident on the nano-brick unit structure under the working wavelength, the linearly polarized light component with the vibration direction consistent with the long axis direction of the nano-brick unit structure is reflected, and the linearly polarized light component with the vibration direction consistent with the short axis direction of the nano-brick unit structure is directly transmitted. Therefore, the nano brick unit structure after optimized design by electromagnetic simulation software can realize the function of polarization light splitting, and is equivalent to a miniature polarizer.

2. Sampling unit design and complex amplitude modulation principle.

(1) And (4) coding the transmittance.

Because the nano brick unit structure can be used as a miniature polarizer, the following requirements are met:

I_out＝I_insin²(Φ-θ) (1)

wherein, I_inIs the intensity of incident light, I_outAnd theta is the included angle between the vibration direction of the incident linearly polarized light and the x axis (the value range of theta is 0-180 DEG) for the light intensity of transmitted light.

From the formula (1), for a given θ, namely the polarization state of incident linearly polarized light, changing the direction angle Φ of the nano-brick unit structure, the light intensity of the transmitted light changes accordingly. Due to sin²(phi-theta) is a periodic even function with two different orientation angles phi₁And phi₂So that the incident light is incident on two beams with different direction angles phi₁And phi₂When the nano-bricks are arranged on the base plate, the light intensity of the transmitted light is the same. When theta is changed, the two beams are incident at different direction angles phi₁And phi₂When the nano-bricks are arranged on the surface of the substrate, the transmitted light intensity is different.

In particular, when the direction angles Φ of the nanoblock unit structures are 22.5 °, 67.5 °, 112.5 ° and 157.5 °, as shown in fig. 4, when the incident light is linearly polarized light with θ ═ 0 °, the transmittances corresponding to the nanoblock unit structures of the four direction angles are 0, 1, and 0, respectively; when the incident light is linearly polarized light with theta being 45 degrees, the transmittances corresponding to the nano-brick unit structures of the four direction angles are respectively 0, 1 and 1, namely when the polarization state of the incident linearly polarized light is changed, the transmittances corresponding to the nano-brick unit structures are also changed, and four codes of 00, 10, 11 and 01 can be formed.

(2) Phase modulation in complex amplitude is achieved using the diffraction effect of an irregular grating.

As shown in FIG. 5, when a plane wave perpendicularly irradiates a line grating, the K-th order diffraction is a plane wave, the equiphase plane is a plane perpendicular to the diffraction direction, assuming that the pitch is constant, andlet d be the pitch of the grating and theta be the smallest diffraction angle of the K-th order_KThen, as can be seen from the grating equation, at θ_KThe optical path difference of the adjacent light rays in the direction is as follows:

L_K＝d sinθ_K＝Kλ (2)

if the grid distance at a certain position is increased by delta, the position is along theta_KThe optical path difference of the directionally adjacent light rays becomes:

L_K’＝(d+Δ)sinθ_K (3)

then theta_KThe phase delay introduced at this location by the directionally diffracted light waves is:

the value of the phase delay is related only to the pitch shift amount and the diffraction order, and it can be seen from equation (4) that by changing the grating pitch locally, a desired phase modulation can be obtained in a certain diffraction direction, and the phase is called a winding phase.

(3) Sampling unit design and complex amplitude modulation principle.

The encoding method for converting a complex-valued function into a real-valued non-negative function is to represent one complex-valued function as two real-valued non-negative functions, i.e. to represent the complex amplitude with two real parameters of amplitude and phase, and to encode the amplitude and phase separately, which is called detour phase encoding.

Assuming that the hologram has a total of M × N sampling units with a sampling interval of δ_xAnd delta_yEach sampling unit contains t × t nano-brick unit structures with uniform size and direction angles Φ of 22.5 °, 67.5 °, 112.5 ° and 157.5 °, as shown in fig. 6, then:

δ_x＝δ_y＝t*C (5)

the complex amplitude of the light wave recorded by the (m, n) th sampling unit on the hologram is set as follows:

wherein A is_mnIs normalized amplitude, i.e. 0 ≦ A_mn≤1；

Is the phase.

The number of the nano-brick unit structures of the sampling unit is kept unchanged, the transmittance of the sampling unit is controlled by changing the number of the nano-brick unit structures of the transmission part of the sampling unit, namely, the light transmission area of the clear aperture is changed to code the amplitude, and meanwhile, the positions of the center of the clear aperture and the center of the sampling unit are changed to code the phase, so that the complex amplitude holography is realized.

In fig. 6, the gray area is composed of the nano brick unit structure with the transmittance of 0, and the area is opaque; the white area represents the transmission part of the sampling unit, namely the light transmission caliber, and is composed of a nano brick unit structure with the transmittance of 1. The width of the light-transmitting aperture is W delta_xW is a constant and has a height L_mnδ_yWith normalized amplitude A_mnIs in direct proportion. P_mnδ_xThe distance between the center of the clear aperture and the center of the sampling unit is proportional to the phase of the sampling unit. The relationship between aperture parameter and complex amplitude is as follows:

the above coding method adopts width modulation in y direction for recording amplitude information; position modulation is used in the x-direction for recording phase information, both of which record complex amplitude information of the light wave. The hologram produced by the encoding method can reproduce a hologram image recorded by the hologram at a specific diffraction order K along the x direction.

3. The method is based on the principle of complex amplitude holographic multiplexing of a sampling unit and a holographic design method.

(1) The complex amplitude information of the hologram is encoded as a 0-1 transmittance matrix of the sampling cells.

Suppose two holograms H₁And H₂The total number of the M multiplied by N sampling units is that the complex amplitude distribution of the (M, N) th sampling unit is respectively

And

h is to be₁And H₂The complex amplitude information of the hologram is encoded by the equation (7) to generate two 0-1 transmittance matrices T including (M × T) x (N × T) elements according to the sampling unit complex amplitude modulation principle, that is, the amplitude is encoded by changing the light transmission area of the clear aperture, the phase is encoded by changing the positions of the center of the clear aperture and the center of the sampling unit, and the phase is encoded by changing the angles θ between the vibration direction and the x axis to 0 ° and θ to 45 °₁And T₂，T₁And T₂The element positions of (a) are in one-to-one correspondence.

(2) The principle of detour phase code multiplexing.

If linear polarized light with an incident angle theta of 0 DEG is assumed, a hologram H is generated correspondingly₁When the 0-1 transmittance matrix of the nano brick unit structure is T₁(ii) a When linearly polarized light with an angle theta of 45 DEG is incident, a hologram H is generated correspondingly₂When the 0-1 transmittance matrix of the nano brick unit structure is T₂。T₁And T₂As can be seen from fig. 4, the transmittance of the nano-brick unit structure at four direction angles of 22.5 °, 67.5 °, 112.5 ° and 157.5 ° when linearly polarized light with θ of 0 ° and θ of 45 ° is incident is 0, 1, 0 and 0, 1 and 1, respectively, and four codes of 00, 10, 11 and 01 can be formed. Thus can change T₁And T₂The transmission rate coded information is generated simultaneously with the matrix, and a direction angle matrix Φ including only four kinds of direction angle information, i.e., 22.5 °, 67.5 °, 112.5 °, and 157.5 °, is obtained from fig. 4. And arranging the nano brick unit structures with consistent (M x t) x (N x t) sizes and direction angles arranged according to the direction angle matrix phi at equal intervals in the x and y directions to form the direction angle information of the super-surface array structure (M x t) x (N x t) nano brick unit structures, and generating the direction angle matrix phi only containing the four kinds of direction angle information of 22.5 degrees, 67.5 degrees, 112.5 degrees and 157.5 degrees.

(3) And designing a complex amplitude type holographic plate based on the super surface array structure.

The complex amplitude type holographic plate based on the super surface array structure is composed of a substrate and a nano brick array on the substrate, wherein the nano brick array is formed by arranging nano brick unit structures with consistent (M x t) x (N x t) sizes and direction angles arranged according to a direction angle matrix phi at equal intervals in the x direction and the y direction, and is shown in figure 8.

When the super-surface array structure is fixed, the polarization state of incident linearly polarized light is adjusted, and the hologram is irradiated by linearly polarized light with θ being 0 ° and θ being 45 °, respectively, the hologram can realize two completely different complex amplitude distribution functions, that is, complex amplitude holographic multiplexing.

The working mode of the complex amplitude type holographic plate is a transmission mode, the substrate material is a silicon dioxide substrate, and the nano brick unit structure material is silver, but not limited thereto.

To sum up, the method for realizing roundabout phase encoding multiplexing based on the super-surface array structure mainly comprises the following steps:

(1) optimizing the size parameter of the nano brick unit structure to be equivalent to a micro polarizer;

(2) the transmittance codes corresponding to the nano brick unit structures;

(3) designing a hologram sampling unit;

(4) and designing a complex amplitude holographic plate based on roundabout phase encoding multiplexing.

The invention will be further explained with reference to the drawings.

In the method for realizing detour phase encoding multiplexing based on the super-surface array structure provided by this embodiment, detour phase encoding multiplexing based on the super-surface array structure is realized for incident linearly polarized light with an included angle θ of 0 ° and an included angle θ of 45 ° between the vibration direction and the x axis, and the function that the hologram can realize two completely different complex amplitude distribution functions when the incident linearly polarized light with θ of 0 ° and the incident linearly polarized light with θ of 45 ° are respectively incident on the hologram, that is, the invention can realize detour phase encoding multiplexing based on the super-surface array structure.

In this embodiment, the nano-unit structure is composed of a silicon dioxide substrate and silver nano-bricks etched on the substrate,selecting a design wavelength of 633nm, and performing optimization simulation on the unit structure of the nano brick by using electromagnetic simulation software CST according to the wavelength to obtain the optimized silver nano brick with the size parameters as follows: the length is 160nm, the width is 80nm, the height is 70nm, and the side length of the unit structure substrate is 300 nm. The reflection and transmission efficiency of the nano-brick unit structure under the structural parameters to linearly polarized light with two orthogonal polarization states vibrating along the major axis and the minor axis directions respectively is shown in figure 3, wherein R_l、T_lRespectively representing the reflectance and transmittance, R, of linearly polarized light vibrating in the major axis direction of the nano-brick unit structure_s、T_sRespectively, the reflectance and transmittance of linearly polarized light vibrating in the minor axis direction of the nanoblock unit structure. As can be seen from FIG. 3, R is measured at the wavelength of the incident light between 550nm and 700nm_lAnd T_sIs relatively high, R_sAnd T_lThe value of (a) is relatively low. Especially at an operating wavelength of 633nm, R_lAnd T_sGreater than 90%, R_sAnd T_lLess than 10 percent, which shows that the linearly polarized light vibrating along the short axis direction almost completely transmits, but the linearly polarized light vibrating along the long axis direction only transmits a small amount of light, namely the optimized nano-brick unit structure can realize the function of polarization and light splitting and can be equivalent to a micro polarizer.

In this embodiment, when the direction angles Φ of the nano-brick unit structures are 22.5 °, 67.5 °, 112.5 ° and 157.5 °, as shown in fig. 4, when the incident light is linearly polarized light with θ being 0 °, the transmittances corresponding to the nano-brick unit structures at the four direction angles are 0, 1 and 0, respectively; when the incident light is linearly polarized light with theta being 45 degrees, the transmittances corresponding to the nano-brick unit structures of the four direction angles are respectively 0, 1 and 1, namely when the polarization state of the incident linearly polarized light is changed, the transmittances corresponding to the nano-brick unit structures are also changed, and four codes of 00, 10, 11 and 01 can be formed.

The sampling unit comprises t multiplied by t four nano brick unit structures with consistent size and direction angles phi of 22.5 degrees, 67.5 degrees, 112.5 degrees and 157.5 degrees, the number of the nano brick unit structures of the sampling unit is kept unchanged, the transmittance of the sampling unit is controlled by changing the number of the nano brick unit structures of the transmission part of the sampling unit, namely the light transmission area of the clear aperture is changed to code the amplitude, and meanwhile, the positions of the center of the clear aperture and the center of the sampling unit are changed to code the phase, so that complex amplitude holography is realized.

Taking a sampling unit at an arbitrary position of the hologram as an example, assuming that T is 8, incident linearly polarized light is linearly polarized light with θ being 0 ° and θ being 45 °, and the 0-1 transmittance matrix of the corresponding sampling unit is T₁And T₂As shown in fig. 7. As can be seen from the figure, when the polarization state of incident light is different, the light transmission area of the corresponding clear aperture and the positions of the center of the clear aperture and the center of the sampling unit are different, so the corresponding complex amplitudes are also different. T is₁And T₂The element positions of (A) are in one-to-one correspondence, and T is set₁And T₂The transmission rate coded information is generated in a matrix-simultaneous manner, and a direction angle matrix Φ including only four kinds of direction angle information, i.e., 22.5 °, 67.5 °, 112.5 °, and 157.5 °, is obtained from the coded information table of fig. 4. The other sampling units of the hologram are designed in the same way, and are not described in detail here.

By adjusting the polarization state of incident linearly polarized light, when a designed hologram is irradiated with linearly polarized light having θ of 0 ° and θ of 45 °, the hologram can realize two completely different complex amplitude distribution functions, that is, complex amplitude holographic multiplexing.

The method for realizing circuitous phase coding multiplexing based on the super-surface array structure provided by the embodiment of the invention at least comprises the following technical effects:

(1) the roundabout phase encoding multiplexing design method provided by the invention is simple, flexible in design and easy to operate, not only can realize complex amplitude holography, but also can generate two completely different holographic sheets by changing the polarization state of incident linearly polarized light so as to realize complex amplitude holography multiplexing;

(2) the super surface material (i.e. super surface array structure) has simple structure, small volume, light weight and compact structure, the related super surface manufacturing process is mature and simple, and can be copied and produced in large scale and at low cost, thereby having great industrialization prospect.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.