Super scattering and zero forward scattering coordinated regulation and control system and method based on optical gain

Abstract

The invention discloses a super scattering and zero forward scattering coordinated regulation system and method based on optical gain, and relates to the technical field of optical scattering enhancement. The method comprises the steps that a space rectangular coordinate system is constructed; the cylindrical scatterer is vertically placed along the z axis; a transverse magnetic wave emitted by an emitting device is incident along the x axis; the emitting device emits the transverse magnetic wave, the transverse magnetic wave interacts with the cylindrical scatterer, and a total magnetic field of a free space in coordinates of the cylindrical scatterer is detected by using a detection device. Scattering coefficients and a total scattering cross section of different scattering channels of the cylinder are obtained based on the total magnetic field, key parameters for controlling scattering intensity and directivity are obtained based on the scattering coefficients and the total scattering cross section, and a scattering pattern is obtained by adjusting the key parameters of the cylindrical scatterer. The invention provides a new way for designing advanced optical devices applied to the fields of sub-wavelength antennas, optical communication, radar sensing, imaging and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of optical scattering enhancement, and particularly to a system and method for synergistically regulating super-scattering and zero forward scattering based on optical gain. Background Art

[0002] Light scattering is one of the core phenomena of the interaction between electromagnetic waves and matter. At the sub-wavelength scale, the enhancement of the scattering cross-section (super-scattering) of scatterers and the regulation of their directionality (such as zero forward scattering) are crucial for the performance of optical devices.

[0003] The super-scattering technology can significantly enhance the scattering cross-section far beyond the single-channel limit by exciting the multipole resonances (such as electric dipole, magnetic dipole, and higher-order modes) of sub-wavelength scatterers, showing important potential in the fields of optical sensing, nano-antennas, and high-resolution imaging. However, existing research mainly focuses on the enhancement of scattering intensity and pays insufficient attention to the fine regulation of scattering directionality (such as forward, lateral, or backward scattering distribution). For example, in the design of super-scattering, although the cooperative excitation of multipole resonances can break through the scattering cross-section limit, its asymmetric radiation pattern often leads to the residual of forward scattering energy (proportion > 30%), which limits the performance of directionality-sensitive devices (such as the decrease in antenna radiation efficiency and the increase in imaging background noise).

[0004] Currently, a few technical solutions that attempt to combine super-scattering and directionality regulation mainly adjust the multipole phase difference through passive structure design (such as geometric symmetry breaking or dielectric layer stacking). However, limited by material loss and mode competition, it is difficult to simultaneously meet the requirements of super-scattering intensity and directionality suppression. In addition, although the introduction of active regulation means (such as externally field-driven tunable materials) can dynamically modulate the scattering direction, due to the high system complexity, harsh implementation conditions, and the inability to completely eliminate the forward or backward scattered light, there is still a large amount of residual energy. It is worth noting that the application of traditional multi-layer scattering structures (such as boron nitride) for realizing super-scattering can compensate for losses and enhance the scattering intensity, but it is prone to multi-mode coupling instability or spontaneous radiation interference, which instead exacerbates the difficulty of directionality regulation. How to achieve high-precision regulation of scattering directionality (such as zero forward, unidirectional lateral, or customized angular distribution) while maintaining super-scattering performance is still an unsolved technical bottleneck in the field of sub-wavelength optical devices.

[0005] Therefore, providing a system and method for synergistically regulating super-scattering and zero forward scattering based on optical gain to solve the difficulties existing in the prior art is an urgent problem for those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a system and method for synergistically regulating hyper-scattering and zero forward scattering based on optical gain, providing a new approach for designing advanced optical devices applied in fields such as sub-wavelength antennas, optical communications, radar sensing, and imaging.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A system for synergistically regulating hyper-scattering and zero forward scattering based on optical gain, comprising a scatterer, a transmitting device, and a detecting device; The scatterer is a non-magnetic gain medium cylindrical scatterer vertically placed with adjustable parameters; The transmitting device emits a transverse magnetic wave perpendicular to the cylindrical scatterer for interacting with the cylindrical scatterer; The detecting device is used to measure the far-field radiation intensity scattered at 360° around the cylindrical scatterer and the magnetic field distribution in the near field.

[0008] Optionally, the scatterer extends infinitely along the vertical direction, and the imaginary part of its complex relative permittivity is negative and extends infinitely.

[0009] Optionally, the transverse magnetic wave emitted by the transmitting device is a transverse magnetic plane wave, and the polarization direction is parallel to the incident plane.

[0010] A method for synergistically regulating hyper-scattering and zero forward scattering based on optical gain, applied to the system for synergistically regulating hyper-scattering and zero forward scattering based on optical gain described in any one of the above, comprising the following steps: Construct a space rectangular coordinate system, place the cylindrical scatterer vertically along the z-axis, and make the transverse magnetic wave emitted by the transmitting device incident along the x-axis; The transmitting device emits a transverse magnetic wave to make the transverse magnetic wave interact with the cylindrical scatterer; Use the detecting device to detect the total magnetic field in free space in the coordinates of the cylindrical scatterer; Obtain the scattering coefficients of different scattering channels of the cylinder and the total scattering cross-section based on the total magnetic field; Obtain the key parameters for controlling the scattering intensity and directivity based on the scattering coefficients and the total scattering cross-section; Obtain a scattering pattern by adjusting the key parameters of the cylindrical scatterer.

[0011] Optionally, the total scattering cross-section includes obtaining the far-field radiation intensity characterized by the scattering cross-section per azimuth angle, and integrating the far-field radiation intensity to obtain the total scattering cross-section.

[0012] Optionally, the key parameter is the scattering coefficient, which is obtained by adjusting the radius and relative permittivity of the cylindrical scatterer.

[0013] As can be seen from the above technical solutions, compared with the prior art, the present invention provides a collaborative regulation system and method for hyper-scattering and zero forward scattering based on optical gain, which has the following beneficial effects: 1) By carefully designing the gain and size of the scatterer, the present invention realizes exceeding the single-channel scattering limit and achieving zero forward scattering, thus realizing a new mechanism of unidirectional hyper-scattering; 2) Through the gain medium, the low-order or high-order scattering channels exceed the single-channel scattering limit, thus significantly enhancing the scattering intensity. In addition, the destructive interference between multiple channels eliminates the forward-scattered light, thus enabling effective control of the scattering direction; 3) The participation of the high-order channels in the present invention further enhances the scattering intensity and improves the directivity, providing a more flexible and efficient way to control the light-matter interaction; 4) The present invention provides a deeper understanding of the interaction between multiple scattering channels and the gain medium, and provides a new way to design advanced optical devices applied in the fields of sub-wavelength antennas, optical communications, radar sensing, imaging, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0015] Figure 1 It is a flowchart of a collaborative regulation method for hyper-scattering and zero forward scattering based on optical gain disclosed by the present invention; Figure 2a It is a schematic diagram of the zero-order scattering cross-section of single-channel hyper-scattering disclosed in an embodiment of the present invention; Figure 2b It is a schematic diagram of the scattering cross-section per angle of single-channel hyper-scattering disclosed in an embodiment of the present invention; Figure 2c It is a schematic diagram of the magnetic field distribution of single-channel hyper-scattering disclosed in an embodiment of the present invention; Figure 3a It is a schematic diagram of the zero-order scattering cross-section of the second-kind Kerker scattering disclosed in an embodiment of the present invention; Figure 3b It is a schematic diagram of the scattering cross-section per angle of the second-kind Kerker scattering disclosed in an embodiment of the present invention; Figure 3c It is a schematic diagram of the magnetic field distribution of the second-kind Kerker scattering disclosed in an embodiment of the present invention; Figure 4a It is a schematic diagram of the zero-order scattering cross-section of the Kerker hyper-scattering disclosed in an embodiment of the present invention; Figure 4bSchematic diagram of the per-angle scattering cross-section of the Kirk super-scattering disclosed in the embodiments of the present invention; Figure 4c Schematic diagram of the magnetic field distribution of the Kirk super-scattering disclosed in the embodiments of the present invention; Figure 5 For the Kirk super-scattering disclosed in the embodiments of the present invention Schematic diagram of the ratio of the forward and backward scattering cross-sections in the parameter space; Figure 6 For the Kirk super-scattering disclosed in the embodiments of the present invention Schematic diagram of the normalized zero-order scattering cross-section in the parameter space; Figure 7 Schematic diagram of the total scattering cross-section, the scattering cross-sections of each scattering channel, and the ratio of the forward and backward scattering cross-sections of the Kirk super-scattering disclosed in the embodiments of the present invention; Figure 8 Schematic diagram of the field distribution of the Kirk super-scattering under software simulation disclosed in the embodiments of the present invention; Figure 9 Schematic diagram of the scattering field distribution of the Kirk super-scattering disclosed in the embodiments of the present invention; Figure 10 Schematic diagram of the parameters of the Kirk super-scattering dominated by high-order modes disclosed in the embodiments of the present invention; Figure 11 Schematic diagram of the scattering cross-sections of each channel of the Kirk super-scattering dominated by high-order modes disclosed in the embodiments of the present invention; Figure 12 Schematic diagram of the total scattering cross-section and the full width at half maximum of the Kirk super-scattering dominated by high-order modes disclosed in the embodiments of the present invention. Detailed implementation manners

[0016] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] The present invention discloses a system for synergistically regulating super-scattering and zero forward scattering based on optical gain, including a scatterer, a transmitting device, and a detecting device; The scatterer is a vertically placed non-magnetic gain medium cylindrical scatterer with adjustable parameters; The transmitting device emits a transverse magnetic wave perpendicular to the cylindrical scatterer for interacting with the cylindrical scatterer; The detecting device is used to measure the far-field radiation intensity scattered at 360° around the cylindrical scatterer and the magnetic field distribution in the near field.

[0018] Furthermore, the scatterer extends infinitely in the vertical direction, and the imaginary part of its complex relative permittivity is infinitely extended with a negative value, and the imaginary part of its complex relative permittivity is negative.

[0019] Furthermore, the transverse magnetic wave emitted by the transmitting device is a transverse magnetic plane wave, and the polarization direction is parallel to the incident plane.

[0020] A method for synergistically regulating hyper-scattering and zero forward scattering based on optical gain, which is applied to the system for synergistically regulating hyper-scattering and zero forward scattering based on optical gain described in any one of the above, referring to Figure 1 shown in the figure, includes the following steps: Construct a spatial rectangular coordinate system, place the cylindrical scatterer vertically along the z-axis, and the transverse magnetic wave emitted by the transmitting device is incident along the x-axis; The transmitting device emits a transverse magnetic wave and makes the transverse magnetic wave interact with the cylindrical scatterer; Use the detection device to detect the total magnetic field in the free space of the cylindrical scatterer coordinates; Based on the total magnetic field, obtain the scattering coefficients and the total scattering cross section of different scattering channels of the cylinder; Based on the scattering coefficients and the total scattering cross section, obtain the key parameters for controlling the scattering intensity and directivity; Obtain the scattering pattern by adjusting the key parameters of the cylindrical scatterer.

[0021] Furthermore, along the positive axis propagation of the incident transverse magnetic (TM, transverse-magnetic or p-polarized) plane wave. For a two-dimensional sub-wavelength scatterer in a homogeneous environment with a refractive index of n in a passive system, the maximum scattering cross section of a single channel cannot exceed , where is the wavelength in free space. is the single-channel scattering limit in the two-dimensional coordinate system. Set a sub-wavelength rod with a radius of r and a relative permittivity of . According to the electromagnetic wave theory, the total magnetic field in the free space in cylindrical coordinates is expressed as: (1), where is the wave number in free space, and are the m-th order of the first kind of Hankel function and Bessel function respectively. is the polar coordinate centered at the origin. The parameter S m , that is, the scattering coefficient of the m-th scattering channel, can be analytically solved by matching the boundary conditions, and the expression is: (2).

[0022] Further, the total scattering cross-section includes obtaining the far-field radiation intensity characterized by the scattering cross-section per azimuth angle, and integrating the far-field radiation intensity to obtain the total scattering cross-section. The expression is: (3), where the scattering cross-section from a single m-th channel , and the total scattering cross-section per azimuth angle correspond to the expressions: (4), (5), where represents the angle between the wave vector of the incident wave and the wave vector of the scattered wave, is the reflection coefficient.

[0023] Further, the key parameter is the scattering coefficient S m , which is obtained by adjusting the radius r of the cylindrical scatterer and the relative permittivity .

[0024] In a specific embodiment, starting from the conceptual diagrams of single-channel superscattering and second-kind Kerker scattering, located at Figures 2a - 2c and Figures 3a - 3c , from the conceptual diagrams, it can be found that single-channel superscattering enhances the intensity of scattering, making a certain scattering channel (the zero-order channel in this example) exceed the single-channel scattering limit; while second-kind Kerker scattering controls the direction of scattering, which is second-kind Kerker scattering in this example, eliminating the forward-scattered light.

[0025] Based on the conceptual diagram of Kerker superscattering, the optimized relative permittivity and scatterer radius are and , Figure 4a indicating that when the incident wave impinges on the optimized scatterer, Kerker-superscattering occurs, and the scattering cross-section of the m = 0 channel exceeds the single-channel scattering limit, while Figure 4b shows the disappearance of the forward-scattered light at this time. The schematic diagram of the magnetic field distribution of Kerker superscattering is shown in Figure 4c .

[0026] From formula (2), note that is a function of the relative permittivity and the radius . From formulas (3)-(5), the conditions for realizing single-channel superscattering and second-kind Kerker scattering depend on S m . Therefore, as well as r provide two degrees of freedom to achieve Kerker-superscattering. Based on this, in The relationship between Kerker scattering of the second kind and superscattering is sought in the parameter space of . , Set to 3, such as Figure 5 As shown, draw based on The second kind of Kerk scattering directly corresponds to the parameter condition to be achieved ,exist Figure 5 The blue area is shown in Figure 6 As shown, draw based on The black dotted line represents the single-channel scattering limit, and the parameter area to the right of the dotted line represents , a single-channel superscattering phenomenon will occur. Figure 5 and Figure 6 The combined analysis of Kerck superscattering parameters determines the corresponding parameter coordinates and ,In this parameter setting, the second type of Kerker scattering and superscattering can be achieved simultaneously.

[0027] The gain parameter of the scatterer is set to . Figure 7 The total scattering cross section and the scattering cross section contributed by each angular momentum channel under this parameter setting are shown in Figure 1. The horizontal dashed line represents the single-channel scattering limit. hour, The channel scattering cross section exceeds the single channel scattering limit, reaching nearly 4.07 times. At the same time, the ratio of forward and backward scattering cross sections reaches a minimum value and approaches zero. COMSOL Multiphysics finite element software is used to numerically simulate the Kerker superscattering phenomenon under optimized parameters. Figure 8 This is a schematic diagram of the magnetic field distribution of Kerke superscattering. As predicted before, after the plane wave is incident, the forward plane waveform is basically undisturbed.

[0028] In order to further explore the effect of each angular momentum channel on the scattering intensity and direction, Figure 9 The distribution diagram of the scattered field and the distribution diagram of the scattered field contributed by each channel are drawn in. The total scattered field is obtained by linear superposition of the scattered fields of each scattering channel through formula (3). The phase and amplitude of the forward scattering field of each channel are regulated by the gain parameter and the size parameter. Under appropriate parameters, zero forward super scattering can be achieved after superposition.

[0029] The previous implementation of Kirk superscattering is based on the superscattering of the gain-coordinated m=0 channel. As the size of the scatterer increases, the higher-order scattering channels have an increasingly greater impact on the total scattered field intensity and direction. Figure 10In [reference], it still remains within the sub-wavelength range. By attempting to increase the radius of the scattering cylinder, it can be found that there are parameters different from those of Kerker super-scattering in Figure 2a [reference]. In Figure 11 [reference], by plotting the contributions of the scattering cross-sections of each scattering channel of Kerker super-scattering with these different parameters, it can be found that the large-size parameters induce the participation of higher-order channels. Due to the participation of higher-order channels, compared with the Kerker super-scattering in the channel, the total scattering cross-section increases, and the full width at half maximum of the far-field radiation pattern decreases, and the directivity is further improved, as shown in Figure 12 .

[0030] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A superscattering and zero forward scattering coordinated control system based on optical gain, characterized in that: It includes a scatterer, a transmitting device and a detecting device; The scatterer is a vertically placed non-magnetic gain medium cylindrical scatterer with adjustable parameters; The transmitting device transmits a transverse magnetic wave perpendicular to the cylindrical scatterer, so as to interact with the cylindrical scatterer; The detection device is used to measure the far-field radiation intensity scattered at 360° around the cylindrical scatterer and the magnetic field distribution in the near field.

2. The optical gain-based superscattering and zero forward scattering coordinated control system according to claim 1, characterized in that: If the scatterer is infinitely extended in the vertical direction, the imaginary part of its complex relative dielectric constant will be negative. If the scatterer is infinitely extended in the vertical direction, the imaginary part of its complex relative dielectric constant will be negative.

3. The optical gain-based superscattering and zero forward scattering coordinated control system according to claim 1, characterized in that: The transverse magnetic wave emitted by the transmitting device is a transverse magnetic plane wave, and the polarization direction is parallel to the incident plane.

4. A method for coordinated control of superscattering and zero forward scattering based on optical gain, applied to a coordinated control system of superscattering and zero forward scattering based on optical gain according to any one of claims 1 to 3, characterized in that: The following steps are involved: Construct a spatial rectangular coordinate system, place the cylindrical scatterer vertically along the z-axis, and let the transverse magnetic wave emitted by the transmitting device be incident along the x-axis; The transmitting device transmits a transverse magnetic wave, so that the transverse magnetic wave interacts with the cylindrical scatterer; Using a detection device to detect the total magnetic field in free space in the coordinates of the cylindrical scatterer; Based on the total magnetic field, the scattering coefficients of different scattering channels of the cylinder and the total scattering cross section are obtained; The key parameters for controlling scattering intensity and directivity are obtained based on the scattering coefficient and total scattering cross section; The scattering pattern is obtained by adjusting the key parameters of the cylindrical scatterer.

5. The method for coordinated control of superscattering and zero forward scattering based on optical gain according to claim 4, characterized in that: The total scattering cross section includes obtaining the far-field radiation intensity by characterizing the scattering cross section at each azimuth angle, and integrating the far-field radiation intensity to obtain the total scattering cross section.

6. The method for coordinated control of superscattering and zero forward scattering based on optical gain according to claim 4, characterized in that: The key parameter is the scattering coefficient, which is obtained by adjusting the radius and relative dielectric constant of the cylindrical scatterer.

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