An all-optical modulated dual-wavelength single-pass optical switch implementation system

Abstract

The application belongs to the technical field of light field modulation of super surface, and discloses a full light modulation two-wavelength single-pass optical switch implementation system. The system comprises, in sequence, a light source unit, a light ray preprocessing unit, a first beam splitter, an objective lens, a sample to be measured, a first lens and a detection unit. Three light rays with different wavelengths are arranged in the light source unit. The light ray preprocessing unit pre-processes the three different light rays after being combined, and then converges the pre-processed light rays on the beam splitter. The first beam splitter is used for transmitting the light from the light ray preprocessing unit to the objective lens. The objective lens is used for irradiating the light rays on the surface of the sample to be measured. The sample to be measured reflects the light rays, and the reflected light rays return to the first beam splitter through the objective lens. The first beam splitter reflects the light rays into the first lens. The parallel light rays emitted from the first lens enter the detection unit. The detection unit is used for measuring the light intensity of the working light and the modulation light. Through the application, the modulation light can independently modulate and control two different wavelength optical signals.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical field modulation of super surface, and more particularly relates to a full-optical modulation dual-wavelength single-pass optical switch implementation system. BACKGROUND

[0002] An optical switch is a key component that can realize high-speed switching and control in optical signals, and has the potential to be widely used in the fields of optical communication, optical computing, and optical sensing. Optical switches have functions such as optical path selection, wavelength conversion, and optical packet switching in optical communication networks, improving the transmission efficiency and reliability of optical communication networks. In optical computing, optical switches can be used for routing and processing of optical signals, enabling high-speed processing and transmission of optical signals. Traditional optical switches mainly rely on electrical or thermal constraints to realize the regulation and control of optical signals. However, these methods have the disadvantages of high energy consumption, slow speed, large size, etc., limiting their application in integrated optical circuits and other fields.

[0003] In recent years, full-optical modulation technology has gradually attracted attention as a new type of optical control method. Full-optical modulation technology directly modulates optical signals using optical effects without the need for electrical or thermal modulation, and has the advantages of fast speed, low energy consumption, small size, and easy integration, and is considered an important technical direction in the next generation of optical communication and optical computing. However, full-optical modulation technology still faces some challenges in practical applications, one of which is the inability of full-optical modulation to simultaneously modulate multiple wavelengths. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application provides a full-optical modulation dual-wavelength single-pass optical switch implementation system, which solves the technical problem that the full-optical modulation scheme cannot simultaneously modulate multiple different wavelengths with different switching states.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, a full-optical modulation dual-wavelength single-pass optical switch implementation system is provided, characterized in that the system comprises an optical source unit, a light line preprocessing unit, a first beam splitter, an objective lens, a sample to be tested, a first lens, and a detection unit arranged in sequence, wherein:

[0006] The light source unit is provided with three beams of light of different wavelengths, two of which are working light and one of which is modulation light, the light preprocessing unit is used for preprocessing the three beams of different light after being combined, and then converging after preprocessing on the beam splitter, the first beam splitter is used for transmitting light from the light preprocessing unit to the objective lens, and the objective lens is used for irradiating light on the surface of the sample to be measured; the sample to be measured reflects the light back to the first beam splitter through the objective lens, and the first beam splitter reflects the light into the first lens, and the parallel light emitted from the first lens enters the detection unit, and the detection unit is used for measuring the light intensity of the working light and the modulation light.

[0007] The nanometer structure of the cubic array is arranged on the sample to be measured, and the power of the modulation light is adjusted during the measurement to change the radiation power density of the light irradiated on the surface of the sample to be measured, thereby changing the temperature of the sample to be measured and further changing the scattering intensity of the sample to be measured, so as to adjust the light intensity of the two beams of working light in the detection unit, and the structure size of the nanometer structure is arranged to ensure that the change trends of the light intensity of the two beams of light are opposite, so as to realize the modulation of the modulation light on the on and off process of the two beams of working light of different wavelengths.

[0008] Further preferably, the substrate of the sample to be measured is a silicon-on-insulator structure, and the nanometer structure is arranged on the silicon-on-insulator structure.

[0009] Further preferably, the light preprocessing unit comprises a speckle elimination unit, a polarizer and a second lens arranged in sequence, the speckle elimination unit is used for eliminating speckle noise in the light beam to realize homogenization processing of the light beam, the polarizer is used for adjusting the polarization state of the light beam, and the second lens is used for converging the light from the polarizer into the beam splitter.

[0010] Further preferably, the speckle elimination unit comprises a third lens, a despeckling assembly and a fourth lens, the third lens is used for converging light from the light source unit into the speckle assembly, the despeckling assembly is used for eliminating speckle, and the fourth lens is used for converting the light from the speckle assembly into a parallel light beam.

[0011] Further preferably, the detection unit comprises a second beam splitter, a third beam splitter, a first detection module, a second detection module and a third detection module, the second beam splitter is arranged behind the first lens and is used for dividing the light emitted from the first lens into two beams, one of which enters the first detection module and the other of which enters the third beam splitter, the third beam splitter is also used for dividing the light into two beams, one of which enters the second detection module and the other of which enters the third detection module.

[0012] Further preferably, the first, second and third detection modules have the same structure, each comprising a filter and a detector, the filter being used to filter light of a selected specific wavelength, and the detector being used to receive light emitted from the filter.

[0013] Further preferably, the light source unit is provided with a first working light source, a second working light source and a modulation light source, and a power adjuster is arranged behind the modulation light source and used to adjust the power of the modulation light.

[0014] Further preferably, a fifth beam splitter and a fourth beam splitter are arranged behind the first working light source and the second working light source respectively, a mirror is arranged behind the power adjuster and used to reflect the modulation light into the fourth beam splitter, the fourth beam splitter is used to reflect the second working light and the modulation light into the fifth beam splitter, and the fifth beam splitter is used to combine the first working light, the second working light and the modulation light into one beam of light.

[0015] Further preferably, the structure size of the nanostructure is determined in the following manner:

[0016] (a) determining the variation trend of the scattering cross section of each corresponding nanostructure according to the on-off state of the two beams of working light, the on state corresponding to a downward trend of the scattering cross section, and the off state corresponding to an upward trend of the scattering cross section;

[0017] (b) constructing a one-to-one database between the scattering cross section of the nanostructure and the structure size of the nanostructure, the structure size of the nanostructure including the length, width and height of the nanostructure;

[0018] (c) searching for the structure size of the nanostructure corresponding to the opposite variation trend of the scattering cross section of the two beams of working light in the database in step (b).

[0019] Further preferably, in step (b), the scattering cross section of the nanostructure is calculated according to the following formula:

[0020]

[0021] wherein C sca_b is the backscattering cross section of the nanostructure, L, W and H are the length, width and height of the nanostructure respectively, λ is the wavelength, ε p and ε m are the complex permittivity of the nanostructure and the environment respectively, and θ is the backscattering detection angle.

[0022] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0023] 1. The application adopts array nanostructure and three beams of different wavelengths, adjusts the radiant power density of the whole light beam by the modulated light in the three beams, indirectly controls the temperature of the nanostructure surface, adjusts the refractive index coefficient of the nanostructure, causes the scattering cross section of the nanostructure to change, changes the scattering intensity of different wavelengths of light in the reflected light of the nanostructure, and controls the on and off states of the two working beams by setting the size of the nanostructure, so as to realize the modulation of the modulated light on the on and off states of the two working beams of different wavelengths.

[0024] 2. The structure size of the nanostructure in the application is determined according to the two working beams of different wavelengths, and the structure feature needs to ensure that the change trend of the scattering cross section formed by the two working beams is opposite, and further ensure that the change trend of the light intensity of the two working beams is opposite.

[0025] 3. The substrate of the sample to be tested in the application is an insulator, and the substrate has a low thermal conductivity, which can reduce the dissipation of the heat energy absorbed by the nanostructure, and cause a significant temperature rise of the top layer of the nanostructure.

[0026] 4. The application adopts three beams of different wavelengths, two modulated beams have different wavelengths, which can ensure that the two beams are in opposite on and off states, and realize the function of single pass; the third beam of power controllable modulated light is different from the wavelengths of the first two beams, which can ensure that the modulated beam and the modulated beam are well separated in the subsequent detection process, and avoid the overlap of the light intensity signals between the modulated beam and the modulated beam.

[0027] 5. The application can realize independent modulation and control of two different wavelength optical signals, adopts all-optical modulation method, utilizes the photo-thermal tuning characteristics of the material itself, has the advantages of double wavelength simultaneous control, and provides a new idea and method for realizing high-speed and low-energy optical switch. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a structure schematic diagram of an all-optical modulation double-wavelength single-pass optical switch implementation system constructed according to the preferred embodiment of the application;

[0029] Figure 2 It is a nanostructure morphology parameter schematic diagram constructed according to the preferred embodiment of the application;

[0030] Figure 3 It is a periodic nanostructure part optional arrangement mode constructed according to the preferred embodiment of the application, wherein (a) is one way of nanostructure array, (b) is another way of nanostructure array, and (c) is another way of nanostructure array;

[0031] Figure 4Temperature field distribution of the used silicon nanostructure under high modulated light beam power density, which is constructed according to the preferred embodiment of the present application;

[0032] Figure 5 Backscattering cross section of the used silicon nanostructure under different wavelengths and different temperatures, which is constructed according to the preferred embodiment of the present application;

[0033] Figure 6 Backscattering cross section of the silicon nanostructure under the first working wavelength, which is constructed according to the preferred embodiment of the present application;

[0034] Figure 7 Backscattering cross section of the silicon nanostructure under the second working wavelength, which is constructed according to the preferred embodiment of the present application;

[0035] Figure 8 Absorption cross section of the used silicon nanostructure under different wavelengths and different temperatures, which is constructed according to the preferred embodiment of the present application.

[0036] Figure 9 Three wavelength field intensity detection images under different modulated light beam power densities, which is constructed according to the preferred embodiment of the present application.

[0037] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein:

[0038] 200 - first working light source, 201 - second working light source, 202 - modulated light source, 203 - power regulator, 204 - mirror, 205 - fourth beam splitter, 206 - fifth beam splitter, 207 - third lens, 208 - de-speckle assembly, 209 - fourth lens, 210 - polarizer, 211 - second lens, 212 - first beam splitter, 213 - objective lens, 214 - sample to be measured, 215 - first lens, 216 - second beam splitter, 217 - first filter, 218 - first detector, 219 - third beam splitter, 220 - second filter, 221 - second detector, 222 - third filter, 223 - third detector. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0040] As shown in the drawings, the present application provides a kind of all-optical modulation dual-wavelength single-pass optical switch implementation system, specifically, refer to Figure 1 the drawings.Figure 1 Wherein the first working light source 200 and the second working light source 201 generate the corresponding light beams of the first working light and the second working light respectively, the modulation light source 202 radiates the modulation light beam, if the modulation light source 202 cannot actively adjust the radiant light power, the power density of the modulation light is adjusted by the optional power regulator 203, in the embodiment, the power regulator adopts a continuously adjustable light attenuation sheet;

[0041] The mirror 204, the fourth beam splitter 205 and the fifth beam splitter 206 are used for combining the three light beams; the third lens 207, the despeckling assembly 208 and the fourth lens 209 jointly constitute a despeckling unit, which is used for realizing the despeckling and beam expanding functions and converting into parallel light beams; the polarizer 210 is used for adjusting the polarization state of the light beam; the second lens 211 and the objective lens 213 project the light beam to the nanostructure surface of the sample to be measured; the reflected light field is collected by the same objective lens 213 and propagated to the detection module through the first beam splitter 212 and the first lens 215;

[0042] The second beam splitter 216 and the third beam splitter 219 cooperate with the first filter 217, the second filter 220 and the third filter 222 to separate the light beams of the three wavelengths, and the spatial intensity distribution of each wavelength is detected by the first detector 218, the second detector 221 and the third detector 223 respectively, the first filter 217, the second filter 220 and the third filter 222 only allow the light of a specific wavelength to pass through.

[0043] In the preferred example, only the reflective light switching mode is shown, and the transmissive light switching mode can also achieve the same function.

[0044] The specific structure of the above system will be introduced below.

[0045] (1) Selection of working light wavelength

[0046] In an embodiment of the application, two working wavelengths that need to be switched are selected, the two working wavelengths can be selected arbitrarily according to actual needs, the first working light is a normally-off wavelength generated by the light source 200, and the second working light is a normally-on wavelength generated by the light source 201.

[0047] Specifically, in the preferred example, the working wavelength is set to 414 nm, and the working wavelength two is 445 nm.

[0048] (2) According to the need to switch two working wavelengths, the morphology parameters of the nanostructure of the silicon material in the optical switch device are determined reversely.

[0049] The method for determining the structure size of the nanostructure will be described below in the manner of reflecting light by the nanostructure.

[0050] (a) determining the change trend of scattering cross section of each corresponding nanostructure according to the on and off state of the two beams of working light, the on state corresponds to the downward trend of scattering cross section, and the off state corresponds to the upward trend of scattering cross section;

[0051] (b) constructing a one-to-one database between the scattering cross section of the nanostructure and the structural size of the nanostructure, the structural size of the nanostructure including the length, width and height of the nanostructure, and the scattering cross section calculation expression is as follows:

[0052]

[0053] Where C sca_b represents the backscattering cross section of the nanostructure, L, W and H represent the length, width and height of the nanostructure respectively, λ represents the wavelength, ε p and ε m represent the complex dielectric constant of the nanostructure and the environment respectively, θ represents the backscattering detection angle, usually-180°; usually-180°.

[0054] For the way of nanostructure transmitting light, the forward scattering cross section calculation formula is used to calculate the scattering cross section, as follows:

[0055]

[0056] ε p and ε m can be further written as

[0057] ”'

[0058] ε p = ε p +i ε p

[0059] ”'

[0060] ε m = ε m +i ε m

[0061] ε p ’ and ε p ” represent the real part and the imaginary part of the complex dielectric constant of the nanostructure respectively, ε m ’ and ε m ” represent the real part and the imaginary part of the complex dielectric constant of the nanostructure respectively. The real part ε’ and the imaginary part ε” of the complex refractive index of the material can be written as

[0062] ε’ = n 2 -k 2

[0063] ε” = 2*n*k

[0064] Wherein, n and k represent the real part and imaginary part of the complex refractive index of the material respectively. The complex refractive index of the silicon material n p +k p The values at different wavelengths λ and temperatures T can be calculated by the following expression

[0065] n p (λ,T)=n a (λ)+δ a (λ)*T

[0066]

[0067] Wherein, n α The non-temperature dependent term of the refractive index coefficient real part, δ α The temperature dependent term of the refractive index coefficient real part.

[0068] (c) In the case of ensuring that the scattering cross section variation trends of the two beams of light calculated in step (a) are opposite, find the structure size of the corresponding nanostructure in the database in step (b).

[0069] Specifically, the applicable nanostructure topography parameters can be found based on the scattering cross section database prepared in advance, or different topography parameter combinations can be traversed to determine the applicable nanostructure topography parameters; the monomer nanostructure topography parameters selected in the preferred example are L=700nm, W=90nm, and H=45nm, as shown in Figure 2 .

[0070] In an embodiment of the present application, in order to improve the photo-thermal conversion efficiency of the silicon nanostructure, for the reflective application scenario, the material can be a silicon-on-insulator structure, that is, the base of the nanostructure is an oxide-silicon layer and a silicon layer from top to bottom, or a single-layer oxide-silicon base; for the transmissive application scenario, only a single-layer oxide-silicon base can be selected to ensure that the two working light beams can well penetrate the base.

[0071] In an embodiment of the present application, the geometric size of the monomer nanostructure is small, and for the application scenario requiring large-area modulation light switching, the selected monomer nanostructure can be arranged in an array, and a periodic array mode, an orthogonal two-dimensional grating, an oblique two-dimensional single-structure grating, and an oblique two-dimensional double-structure grating, as shown in Figure 3 , but not limited to these modes.

[0072] In an embodiment of the present application, the finite element method is used to calculate the back scattering cross section, the front scattering cross section, the total scattering cross section and the absorption cross section of the selected nanostructure at different wavelengths and different temperatures, and the optical parameter-refractive index variation of the silicon material at different temperatures needs to be considered. The back scattering cross section is shown in Figure 5 .

[0073] (3) Selection of modulation light

[0074] The wavelength of the modulated light beam is selected to be different from the first working light and the second working light to ensure that the light beams corresponding to the three wavelengths can be properly separated after beam combination, avoiding optical signal crosstalk between different wavelengths.

[0075] Preferably, the wavelength of the modulated light is calculated in advance to find the place with stronger absorption cross section of the nanostructure, which can improve the photo-thermal efficiency and reduce the power density requirement of the modulated light beam. In the preferred example, the wavelength of the modulated light beam is set to 532 nm, and the temperature field distribution after photo-thermal effect is shown in Figure 4 .

[0076] The calculation method of the absorption cross section of the nanostructure is as follows

[0077]

[0078] where Cabs represents the absorption cross section of the nanostructure, and the absorption cross section is shown in Figure 8 .

[0079] The radiation power density of the modulated light is adjusted to control the switching of the light beams corresponding to the first working light and the second working light.

[0080] As shown in Figure 9 , specifically, the radiation power density of the modulated light is adjusted to indirectly control the temperature of the silicon nanostructure, and the refractive index coefficient of silicon material is different at different temperatures, resulting in changes in the scattering cross section of the nanostructure, which directly determines the scattering intensity, thereby realizing all-optical control of the first working light and the second working light optical switch, and the switching states of the first working light and the second working light are opposite, that is, a double-wavelength single-pass optical switch.

[0081] Specifically, the scattering cross section at different temperatures for the first working light is shown in Figure 6 , and the scattering is enhanced with the increase of temperature, so this wavelength is in a normally closed state; the scattering cross section at different temperatures for the second working light is shown in Figure 7 , and the scattering is weakened with the increase of temperature, so this wavelength is in a normally open state.

[0082] In the detection unit, the wavelength filter is used to separate the light beams corresponding to the first working light, the second working light and the modulated light beam, and three detectors are used to detect the light beam spatial intensity distribution corresponding to different modulated light radiation power densities, as shown in Figure 9 .

[0083] In one embodiment of the present application, a scenario is considered to facilitate the presentation of the method of the present application. The diameter of the modulated light beam is half of the first working light and the second working light. When the modulated light beam is in the low power state, the first working light is in the normally closed state, and the intensity detected by the detector is low; the second working light is in the normally open state, and the intensity detected by the detector is high, as shown in the upper image of FIG. 1. Figure 9 When the modulated light beam is in the high power state, the first working light and the modulated light beam coincide in the region which is converted to the open state, the intensity of the working light beam is enhanced in the coincident region, and the intensity in the non-coincident region is low; the second working light and the modulated light beam coincide in the region which is converted to the closed state, the intensity of the working light beam is weakened in the coincident region, and the intensity in the non-coincident region is maintained strong, as shown in the lower image of FIG. 1. Figure 9

[0084] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A dual-wavelength single-pass optical switch implementation system with all-optical modulation, characterized in that: The system includes a light source unit, a light preprocessing unit, a first beam splitter, an objective lens, a sample to be measured, a first lens, and a detection unit, which are arranged in sequence, wherein: The light source unit is provided with three beams of light of different wavelengths, two of which are working light and one is modulated light. The light preprocessing unit is used to preprocess the three different light beams after combining them, and then converge the preprocessed light on the beam splitter. The first beam splitter (212) is used to transmit the light from the light preprocessing unit to the objective lens (213). The objective lens (213) is used to irradiate the light on the surface of the sample to be tested (214). The sample to be tested (214) reflects the light and then passes through the objective lens (213) back to the first beam splitter (212). The first beam splitter (212) reflects the light and enters the first lens (215). The parallel light emitted from the first lens (215) enters the detection unit. The detection unit is used to measure the light intensity of the working light and the modulated light. The sample to be tested (214) is provided with nanostructures in the form of cubes distributed in an array. During the measurement process, the power of the modulated light is adjusted to change the radiation power density of the light irradiated on the surface of the sample to be tested, thereby changing the scattering intensity of the sample to be tested, thereby adjusting the light intensity of the two working lights in the detection unit. At the same time, by setting the structural size of the nanostructure, the change trends of the light intensity of the two beams of light are opposite, thereby realizing the modulation of the on and off process of the two working lights of different wavelengths by the modulated light.

2. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 1, characterized in that: The substrate of the sample to be tested (214) is a silicon-on-insulator structure, and the nanostructure is arranged on the silicon-on-insulator structure.

3. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 1 or 2, characterized in that: The light pre-processing unit comprises a speckle elimination unit, a polarizer (210), and a second lens (211) which are arranged in sequence. The speckle elimination unit is used to eliminate speckle noise in a light beam and realize light beam homogenization. The polarizer (210) is used to adjust the polarization state of the light beam. The second lens (211) is used to converge light from the polarizer into the beam splitter.

4. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 3, characterized in that: The speckle elimination unit comprises a third lens (207), a despeckle assembly (208) and a fourth lens (209); the third lens (207) is used to converge light from a light source unit into the speckle assembly (208); the despeckle assembly (208) is used to eliminate speckles; and the fourth lens (209) is used to convert the light from the speckle assembly into a parallel light beam for outgoing emission.

5. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 1 or 2, characterized in that: The detection unit includes a second beam splitter (216), a third beam splitter (219), a first detection module, a second detection module and a third detection module. The second beam splitter (216) is arranged behind the first lens (215) and is used to split the light emitted from the first lens (215) into two beams, one beam entering the first detection module and the other beam entering the third beam splitter. The third beam splitter (219) is also used to split the light into two beams, one beam entering the second detection module and the other beam entering the third detection module.

6. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 5, characterized in that: The first detection module, the second detection module and the third detection module have the same structure and all include a filter and a detector. The filter is used to filter light of a selected specific wavelength, and the detector is used to receive light emitted from the filter.

7. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 1 or 2, characterized in that: The light source unit is provided with a first working light source (200), a second working light source (201) and a modulated light source (202); a power regulator (203) is provided behind the modulated light source (202) for regulating the power of the modulated light.

8. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 7, characterized in that: A fifth beam splitter (206) and a fourth beam splitter (205) are respectively provided behind the first working light source (200) and the second working light source (201); a reflector (204) is provided behind the power regulator (203) for reflecting the modulated light into the fourth beam splitter (205); the fourth beam splitter (205) is used to reflect the second working light and the modulated light into the fifth beam splitter (206); and the fifth beam splitter (206) is used to combine the first working light, the second working light and the modulated light into one beam.

9. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 7, characterized in that: The structural dimensions of the nanostructure are determined in the following manner: (a) determining a change trend of the scattering cross section of each corresponding nanostructure according to the on and off states of the two working light beams, wherein the normally-on state corresponds to a decreasing trend of the scattering cross section, and the normally-off state corresponds to an increasing trend of the scattering cross section; (b) constructing a database of one-to-one correspondence between the scattering cross section of the nanostructure and the structural dimensions of the nanostructure, wherein the structural dimensions of the nanostructure include the length, width, and height of the nanostructure; (c) Searching the database in step (b) for the structural dimensions of the nanostructure that result in opposite trends in the scattering cross sections of the two working light beams.

10. The all-optical modulated dual-wavelength single-pass optical switch implementation system according to claim 9, characterized in that: In step (b), the scattering cross section of the nanostructure is calculated according to the following formula: Among them, C sca_b is the backscattering cross section of the nanostructure, L, W and H are the length, width and height of the nanostructure respectively, λ is the wavelength, ε p and ε m are the complex dielectric constants of the nanostructure and the environment, respectively, and θ is the backscattering detection angle.

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