CN114910177A - Method for exciting spin Hall effect by using electron beam and control method thereof - Google Patents
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Abstract
The invention discloses a method for exciting a spin Hall effect by using an electron beam and control thereof, wherein plasmon resonance is generated by bombarding a metal nano structure by the electron beam, so that the radiation directions of left and right spin polarization components are separated, the spin Hall effect is excited, and the switching of the light spin Hall effect presence-absence and the left and right spin polarization light radiation directions can be realized by moving the electron beam to change an excitation area, so that the control of the spin angular momentum of light is realized. The invention firstly utilizes the electron beam incidence to generate the optical spin Hall effect, breaks through the optical diffraction limit through the electron beam ultrahigh spatial resolution, realizes the detection of the optical spin Hall effect under the sub-wavelength scale, greatly reduces the control scale of the photon spin angular momentum freedom degree, has the characteristics of small scale, high sensitivity, strong robustness and the like, and can be applied to the fields of optical spin and orbit coupling research, nano photonics information carrier research, quantum information device integration and the like.
Description
Technical Field
The invention relates to excitation of a spin hall effect, in particular to a method for modulating photon spin angular momentum by using a spin hall effect excited by a plasmon generated by bombarding metal with an electron beam and then exciting the spin hall effect, which can analyze the excitation of the spin hall effect and the modulation of the spin angular momentum and guide the application of quantum information devices.
Background
The Spin Hall Effect (SHE) originally described the separation of spintronics present in materials, its discovery provided a unique approach to the transfer and storage of information via the electron spin degree of freedom and opened up the field of research in spintronics. Since two different circular polarization states of light correspond to two spins (σ ═ 1), this spin-dependent effect can be further generalized to the optical domain and is called the Optical Spin Hall Effect (OSHE). By utilizing the optical spin Hall effect, the separation of light with different spins on space can be realized, which has great significance for the transmission and processing of optical information by utilizing the spin freedom of photons.
The optical spin hall effect provides a method of manipulating the angular momentum of the spin of photons. The research on the spin-orbit coupling theory related to photon spin separation and the application research in the aspects of super surface materials, planar micro-cavities, precision measurement and the like are all paid attention by researchers. Due to the enormous value that the optical spin hall effect shows in theoretical research and practical applications, more and more researchers have been working on realizing and studying this optical effect in various optical structures in recent years, such as dielectric cylinders, metal nanoparticles, plasmonic waveguides, and metamaterial materials, among others. Because the spin angular momentum of photons can be used as an information carrier with high robustness and large capacity, the optical spin Hall effect is predicted to realize the manipulation of the information carrier in quantum information. The characteristics of orthogonality and high dimension have wide application prospect in the aspects of information coding and information cryptography. The related research for manipulating the optical spin hall effect mainly focuses on the related research of the Berry Phase (Berry Phase), and the spatial separation of different spin components and the separation of radiation directions are realized by designing the structure of the super-surface. In future application of quantum information technology, the optical spin Hall effect needs to realize modulation of photon spin angular momentum by nanoscale, and is beneficial to integration of quantum devices and construction of quantum networks.
On the other hand, with the development of integrated photonics, many optical structures reach sub-wavelength dimensions, especially plasmon structures, and therefore, realization of excitation and detection with high spatial resolution at sub-wavelength and even deep sub-wavelength scales becomes more and more important for studying optical properties of micro-nano structures. The cathode fluorescence (CL) microscopy excites a micro-nano structure by using a highly focused electron beam and collects a cathode fluorescence signal of a sample, so that cathode fluorescence imaging with extremely high spatial resolution (10 nm) can be realized, abundant optical characteristics of the nano structure can be researched by dynamic local excitation, detection and characterization of a local electromagnetic field mode are realized, and the CL microscopy has an important role in research of micro-nano photonics. Further, under the excitation of electron beams, the electron beam excitation site with a sub-wavelength scale moves to directly modulate the density of local photon states, and the manipulation of far-field cathode fluorescence signals is realized. The angular resolution cathode fluorescence microscopy technology is utilized to realize the characterization of photon radiation direction, the optical polarization detection module is combined to realize the characterization of polarization information and photon spin angular momentum in cathode fluorescence signals, the polarization-related optical phenomenon is detected in a super-fine resolution mode on a nanometer scale, and related application scenes are explored. In the study of plasmonic nanostructures, cathode fluorescence microscopy has revealed many optical properties and phenomena that cannot be studied with conventional optical detection methods, such as buried optical chirality in achiral structures and directed optical radiation in disc-shaped nanoparticles.
Disclosure of Invention
The invention aims to provide an excitation method for realizing the optical spin Hall effect by using an electron beam, so that the electron beam excitation without spin injection can modulate the photon spin angular momentum through plasmon resonance supported by a metal nano structure.
The technical scheme of the invention is as follows:
an excitation method of optical spin Hall effect (see figure 1) is used for modulating photon spin angular momentum without spin injection, and comprises three aspects of processing and preparing a metal nano structure, bombarding the metal nano structure by electron beams to excite the optical spin Hall effect, and controlling the nano scale of the photon spin angular momentum.
The metallic nanostructures are rectangular and are typically fabricated on an insulating substrate (e.g., SiO) 2 a/Si substrate). The processing and preparation steps of the metal nano structure are as follows: 1. preparing a nano-mode pattern on a substrate by an electron beam etching method; 2. processing the rectangular metal nano structure by an electron beam evaporation method.
The metal nano structure is preferably a rectangle with the length of 150-250 nm and the width of 50-100 nm, and the thickness of the metal nano structure is preferably 30-60 nm. The material of the metal nanostructure is preferably a metal such as gold, silver, and aluminum that generates plasmon resonance.
The optical spin hall effect is generated by electron beam bombardment of a specific position of the metal nano structure for excitation. The electron beam bombards the metal nano structure to generate plasmon resonance, and due to the small excitation area, a circular polarization electromagnetic mode formed by superposition of a dipole electromagnetic mode and a quadrupole electromagnetic mode can be formed by accurate excitation in the right center of the long edge of the rectangle. The directions of the radiation electric fields of the dipole electromagnetic mode and the quadrupole electromagnetic mode towards the left side and the right side are mutually vertical, the phase difference exists between the two electric field components, the optical field propagating towards the two sides after the superposition of the electric fields is circularly polarized light with opposite spin, and the excitation light has the spin Hall effect (see figure 2).
The metal nanostructure optical spin angular momentum control is generated by the movement of the electron beam excitation position in a nanoscale, the electron beam bombards the center of the long edge of the rectangle to generate a circular polarization dipole and a circular polarization quadrupole electromagnetic mode which are perpendicular to each other, the excitation position of the electron beam is changed to realize the phase switching of the circular polarization dipole electromagnetic mode, and then the radiation direction of the left-handed rotation and the right-handed rotation is generated to be adjusted, so that the photon spin angular momentum control is realized. The phenomenon of separation of the left and right optical rotation radiation directions is not observed when the electron beam bombards the right center of the rectangle. Therefore, the existence of the optical spin Hall effect and the switching of the left and right optical rotation radiation directions can be realized by moving the electron beam to change the excitation area, so that the control of the optical spin angular momentum is realized (see figure 2).
The electron beam excited light spin Hall effect provided by the invention is characterized in that the regulation and control of photon spin angular momentum are realized by exciting a plasmon by using an electron beam, the spatial separation of left-handed and right-handed components of a light beam is realized through a metal nano structure circular polarization electromagnetic mode under the condition of no spin injection, the detection of the photon spin Hall effect under the sub-wavelength scale is realized, the control scale of the photon spin angular momentum freedom degree is greatly reduced, and the excitation position is accurately changed through the electron beam nano scale movement so as to change the metal nano structure electromagnetic mode and realize the sub-wavelength scale control of the photon spin angular momentum. The invention aims at the research of a new generation of information carrier of nanophotonics, the control of the spin degree of freedom is changed from the traditional far-field laser excitation into the excitation by utilizing a metal plasmon through near-field interaction, and the optical diffraction limit is broken through. The method can be applied to optical spinning and orbit coupling research and quantum information device integration, and has the characteristics of small scale, high sensitivity, high robustness and the like. On the premise of exciting the optical spin Hall effect under the large scale by generally applying a far-field optical mode at present, the electron beam excited plasmon induced optical spin Hall effect at room temperature and the photon spin angular momentum regulation and control have wide market prospects.
Drawings
FIG. 1 shows a sample structure and phenomena schematic of an embodiment of the present invention.
FIG. 2 is a schematic diagram of the excitation light spin Hall effect of the metal nanostructure bombarded by electron beam according to the present invention.
Fig. 3 shows different gyric plasmon resonance hot spot modes of the metal nanostructure under the excitation of 30keV electron beams in the embodiment of the invention.
FIG. 4 shows the spectral components of the cathode fluorescence and the chiral intensity of the cathode fluorescence of the metal nanostructure with the left-handed circular polarization and the right-handed circular polarization under the excitation of 30keV electron beams in the embodiment of the invention.
FIG. 5 shows the left-right rotation signal radiation direction pattern at different electron beam excitation sites at the center wavelength for the metal nanostructure numerical simulation in the embodiment of the present invention.
FIG. 6 shows the fluorescence scattering intensity of the levorotatory circularly polarized cathode under the excitation of 30keV electron beam in the metal nanostructure in the embodiment of the present invention, wherein "upper", "middle" and "lower" represent the electron beam bombardment sites located at the middle point of the upper edge, the middle point and the middle point of the lower edge of the rectangular metal nanostructure, respectively.
FIG. 7 shows the fluorescence scattering intensity ratio of left-handed and right-handed circularly polarized cathodes of a metal nanostructure excited by 30keV electron beams in an embodiment of the present invention, wherein "upper", "middle" and "lower" represent the electron beam bombardment sites located at the middle point of the upper edge, the middle point of the rectangle, and the middle point of the lower edge of the rectangular metal nanostructure, respectively.
FIG. 8 shows the radiation direction pattern of right and left circularly polarized cathode fluorescence at the central wavelength under light excitation of the metal nanostructure numerical simulation in the embodiment of the present invention.
FIG. 9 shows the left-right circular polarized cathode fluorescence radiation direction mode under the excitation of electron beams by numerical simulation of metal nanostructures with different sizes in the embodiment of the invention.
FIG. 10 shows the left-right circular polarization cathode fluorescence radiation direction pattern of different electron beam excitation sites at off-center wavelengths for numerical simulation of metal nanostructures in an embodiment of the present invention.
FIG. 11 shows the application of the spin Hall effect of the electron beam excitation light in spin coding.
Detailed Description
The present invention will be described in further detail below with reference to specific embodiments thereof, so that those skilled in the art can more clearly understand the present invention.
The electron beam excited light spin Hall effect is realized by using electron beams to bombard metal nano structures to generate plasmon resonance. The structure of the experimental sample in this example is shown in FIG. 1: comprises a Si substrate 1, SiO 2 A spacer layer 2 and a metal nanostructure 3, wherein the SiO is 2 The spacing layer 2 is positioned on the Si substrate 1, and the metal nano structure 3 is positioned on SiO 2 On top of the spacer layer 2. The excitation of the electron beam to the metal plasmon resonance in the invention is based on the reciprocity principle of the electron beam excitation and the circularly polarized light irradiation: the rectangular metal nano structure can support a base oscillating along the long edge direction under the excitation of x and y polarized lightThe present electromagnetic mode. When the polarization mode is switched to circularly polarized light incidence, the electromagnetic mode can also be effectively excited, the left (right) circularly polarized light incidence introduces a phase difference of 90 degrees (-90 degrees), the phase difference between the final electromagnetic modes is 180 degrees (0 degrees), dipole moments generate plasmon hot spots at upper left (upper right) angles and lower right (lower left) angles along the rectangular diagonal direction, and a circularly polarized dipole electromagnetic mode is formed. As shown in fig. 3, when the electron beam bombards the position of the metal nanostructure corresponding to the plasmon hotspot, the metal nanostructure can generate a circularly polarized dipole electromagnetic mode similar to that when circularly polarized light is incident, and radiate circularly polarized emergent light corresponding to the incident circularly polarized state. When the excitation site is positioned at the center of the long edge of the metal nano structure or the center of the metal nano structure, the excitation of an electron beam of a circular polarization plasmon hot spot is avoided, and the intensity of the left-handed component and the intensity of the right-handed component of emergent light are equal.
In order to find out a proper wavelength for realizing the optical spin hall effect, an optical circular dichroism signal (figure 4) under the excitation of an electron beam is obtained through the collection of different spinnability spectrums in an experiment, and a calculation formula of the optical circular dichroism far-field signal is as follows:
CD＝(CL LCP -CL RCP )/(CL LCP +CL RCP )
in the above formula, CD represents circular dichroism spectrum, CL LCP Left-handed cathodoluminescence, CL, representing radiation of metallic nanostructures RCP Representing the right-handed cathodoluminescence of the metallic nanostructure radiation.
The preparation method of the experimental sample for the electron beam excitation light spin Hall effect is further provided as follows, and comprises the following steps:
step one, depositing SiO on Si substrate 1 by using Plasma Enhanced Chemical Vapor Deposition (PECVD) 2 Spacer layer 2, obtaining SiO 2 a/Si substrate.
Step two, to SiO 2 The method comprises the following steps of carrying out ultrasonic cleaning on a silicon substrate by using an organic solvent, carrying out ultrasonic cleaning in the sequence of acetone (cleaning time 10-15min) → ethanol (cleaning time 10-20min) → deionized water (cleaning time 20-30min), and finally blowing the deionized water remained on the substrate by using a nitrogen gun to obtain clean SiO 2 Si linerAnd (4) bottom.
Step three, the SiO obtained in the last step 2 The upper surface of the/Si substrate was spin-coated with PMMA A2 glue (3000rad/s, 51s) and dried at 180 ℃ for 5 min. The designed structure shape was then etched out using an Electron Beam Lithography (EBL) system and developed in a developing solution (MIBK) (about 50s), fixed in an isopropyl alcohol solution immediately after development (about 5min), and the sample was then removed and dried with a nitrogen gun. Then, the selected gold target material is vapor-deposited by electron beam evaporation. And finally, putting the whole sample into an acetone solution for about 5 hours, and finally stripping the whole sample by using an acetone solution flushing method to obtain the metal nano structure 3.
The measurement procedure of the electron beam optical spin hall effect excitation is given below: the electron beam spin Hall effect excitation is carried out in a scanning electron microscope-based cathode fluorescence microscopic imaging system, an electron beam penetrates through a small hole of a parabolic mirror above a sample to excite the sample, the radiated cathode fluorescence is collected by the parabolic mirror above the sample, and is finally captured by a Complementary Metal Oxide Semiconductor (CMOS) element through a collection light path, the circular polarization component of the cathode fluorescence of the sample is extracted through a quarter-wave plate and a linear polarizer which are arranged on the collection light path, the long axis of the quarter-wave plate and the polarization direction of the linear polarizer form +/-45 degrees, and the left-handed circular polarization component and the right-handed circular polarization component can be respectively extracted. In the cathode fluorescence detection, a cathode fluorescence spectrum of a sample is collected in a Pan mode, and a filter is arranged on a collection light path to detect information of an optical angle-resolved radiation direction in a Mono mode, so that a cathode fluorescence image of the sample in a selected wavelength range is detected.
Example 1
A three-layer metal nanostructure sample was prepared by processing according to the above steps, as shown in FIG. 1, with a Si substrate 1 from bottom to top and SiO of 100nm thickness 2 A spacer layer 2, a 200nm long, 80nm wide, 30nm high rectangular metal nanostructure 3. In the numerical simulation, the plasmon resonance peak position generated by the excitation of the rectangular metal nano-structure electron beam is 630nm, which is consistent with the cathode fluorescence spectrum obtained by experimental detection. Experimental measurements in a scanning Electron microscope (FEI Quattro C)Is carried out by using a cathode fluorescence microscopic imaging system (Sparc) to detect a cathode fluorescence signal of a sample in a wavelength range of 500nm to 800nm by a Pan mode using a quarter wave plate (AQWP10M-600, THORLABS) and a linear polarizer (LPVIS100, THORLABS), and to collect angle-resolved radiation direction information of the sample at a wavelength of 650nm and a cathode fluorescence image by placing a notch filter having a central wavelength of 650nm in a light path in a Mono mode.
The sample is sent into a vacuum chamber, an electron beam with 30keV is used for bombarding the metal nano structure at room temperature, spectroscopic characteristics of plasmon resonance under different rotation properties are collected and obtained (see figure 4), the peak values of fluorescence signals under three polarization states of left-rotation circular polarization, right-rotation circular polarization and full polarization are all located at 630nm, and the plasmon resonance peak position of the metal nano structure is matched with the optical circular dichroism peak position.
Respectively bombarding the middle point of the upper edge, the middle point of the lower edge and the central position of the rectangle of the long edge of the rectangular metal nano structure by using a 30keV electron beam, collecting radiation direction information (see figure 5) of left-handed circular polarization and right-handed circular polarization cathode fluorescence signals generated under the excitation of three positions, and collecting the wavelength range which is positioned near the peak value of the fluorescence signals at about 630 nm. It can be seen that when the electron beam excites the middle point of the upper edge and the middle point of the lower edge of the long side of the metal structure, the phenomenon that the radiation directions of the left-handed circular polarization component and the right-handed circular polarization component are not consistent occurs, namely, the radiation direction of the left-handed circular polarization component is located in the left hemisphere (see fig. 5), the radiation direction of the right-handed circular polarization component is located in the right hemisphere, the radiation direction of the left-handed circular polarization component is located in the right hemisphere, and the radiation direction of the right-handed circular polarization component is located in the left hemisphere, namely, the two positions are excited to generate the phenomenon that the radiation directions of the left-handed circular polarization component and the right-handed circular polarization component are separated, the left-handed circular polarization hotspot and the right-handed circular polarization hotspot are not excited, the left-handed intensity ratio and the right-handed circular polarization component intensity ratio is near 1 (see fig. 7), which means that the intensities of the left-handed circular polarization component and the right polarization components are basically equal, and the phenomenon can be considered to generate the effective optical spin hall effect. When the electron beam bombards the central position of the rectangle, the radiation directions of the left-handed and right-handed circular polarization components are not obviously separated, and the phenomenon of effective optical spin Hall effect is not considered to be generated. Considering the size of the beam spot of the electron beam is about 10nm multiplied by 10nm, the light spin Hall effect phenomenon can be realized from the existence to the nonexistence by moving the electron beam from the middle point position of the upper edge of the metal structure to the central position of the rectangle, and the radiation direction of the left-right rotation circular polarization component can be realized by moving the electron beam from the middle point position of the upper edge of the metal structure to the middle point position of the lower edge of the metal structure by about 80 nm.
To further verify the specificity of the electron beam for realizing the optical spin hall effect, the same metal nano structure is excited by using white light, and radiation direction information of left-right circular polarization components and full polarization is collected, and fig. 8 shows an angle-resolved detection result, the radiation intensity in each direction is basically the same, and the optical spin hall effect phenomenon is not shown. Therefore, it can be judged that the photon spin angular momentum can not be regulated by light excitation for a single rectangular metal nano structure. In order to further study the influence of the size of the metal nanostructure on the realization of the optical spin hall effect of the electron beam, radiation direction information of left and right spin polarization components excited by the electron beam of the rectangular metal nanostructure with different sizes is collected (see fig. 9), and the optical spin hall effect phenomenon is obvious under the size of the larger nanostructure. In order to further study the influence of the detection waveband on the realization of the optical spin Hall effect of the electron beam, radiation direction information of left and right spin polarization components excited by the electron beam with the metal nano structure under different central wavelengths is collected (see figure 10), and the optical spin Hall effect phenomenon is weakened at a position far away from the peak value of a fluorescence signal.
The electron beam excited light spin Hall effect provides a new mode of regulating photon spin angular momentum in a nanometer scale, provides a new information carrier of photon spin, and has wide application prospect in the fields of optical information and quantum information. FIG. 11 shows the application of the present invention to spin coding. A far field angle resolution mode that the radiation direction of the left-handed circular polarization component is positioned in a left hemisphere and the radiation direction of the right-handed circular polarization component is positioned in a right hemisphere is defined as '0'; defining a far field angle resolution mode that the radiation direction of the left-handed circular polarization component is positioned in the right hemisphere and the radiation direction of the right-handed circular polarization component is positioned in the left hemisphere as '1'; and defining a far field angle resolution mode with the left and right rotation circular polarization component radiation directions not separated as an erasure code so as to improve the accuracy of the coded information. The three modes of '0', '1' and an erasure code are respectively corresponding to the positions of an electron beam excitation site at the middle point of the upper edge, the middle point of the lower edge and the center of a rectangle of the long edge of the metal nanostructure. The whole encoding process is integrated in a metal structure nanometer unit with a sub-wavelength scale. By designing the scanning path of the electron beam, the output of different coded information is realized. The photon spin coding provides a coding mode different from the level intensity, and the new information carrier improves the information carrying capacity of optical signals. The electron beam excited light spin Hall effect provides a mode of controlling photon spin angular momentum in a sub-wavelength scale, and improves the integration level in the application of information devices.
The invention firstly utilizes the light spin Hall effect generated by the incidence of the electron beam, breaks through the optical diffraction limit through the ultrahigh spatial resolution of the electron beam, accurately excites the metal nano structure to generate a circular polarization electromagnetic mode, and realizes the separation of the left-handed component and the right-handed component of the cathode fluorescence signal in the radiation direction. The metal nanostructure plasmon resonance enables electron beams not carrying a single spin state to be incident with circularly polarized light carrying the single spin state to generate a consistent optical spin Hall effect phenomenon, and is different from a traditional far-field optical excitation mode for researching photon angular momentum control. The invention relates to a novel optical spin Hall effect excitation and photon spin angular momentum control method with nanoscale, high sensitivity and strong robustness, which is suitable for metal super surfaces of other structures besides a metal rectangular nano structure.
Finally, it is noted that the disclosed embodiments are intended to aid in the understanding of the invention, and those skilled in the art will understand that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (10)
1. An excitation method of a light spinning Hall effect is characterized in that an electron beam bombards a metal nano structure to generate plasmon resonance, so that the radiation directions of left and right spinning circular polarization components are separated, circularly polarized light with opposite spinning directions is transmitted to two sides, and the light spinning Hall effect is excited, wherein the metal nano structure is a rectangular metal nano structure, and the electron beam bombards the middle point of the long edge of the rectangular metal nano structure.
2. The excitation method of the optical spin hall effect according to claim 1, wherein the metal nanostructure is a rectangle having a length of 150 to 250nm and a width of 50 to 100nm, and has a thickness of 30 to 60 nm.
3. The excitation method of the optical spin hall effect as claimed in claim 1, wherein the material of the metal nanostructure is gold, silver or aluminum.
4. The method for exciting an optical spin hall effect according to claim 1, wherein the metal nanostructure is formed on an insulating substrate, a nano-mode pattern is formed on the substrate by an electron beam lithography method, and then a rectangular metal nanostructure is formed by an electron beam evaporation method.
5. The method of exciting the optical spin hall effect of claim 4 wherein said insulating substrate is SiO 2 a/Si substrate.
6. A method for controlling the spin angular momentum of light, bombarding a rectangular metal nanostructure by using an electron beam: when electron beams bombard the middle points of the long edges of the rectangular metal nano structure, the radiation directions of left-handed and right-handed circularly polarized components are separated, circularly polarized light with opposite spin directions is transmitted to two sides, and when the bombarding position is switched between the middle points of the two long edges, the radiation direction of the generated left-handed and right-handed circularly polarized light is reversed; when the electron beam bombards the center of the rectangular metal nano structure, the radiation directions of the left-handed and right-handed circular polarization components are not separated; the bombardment position of the electron beam is switched between the middle points of the long edges of the rectangular metal nano structure and the center of the rectangular metal nano structure to realize the regulation and control of the optical spin Hall effect, and the bombardment position of the electron beam is switched between the middle points of the two long edges of the rectangular metal nano structure to realize the switching of the optical radiation direction of the left-right spin circular polarization light, thereby realizing the control of the optical spin angular momentum.
7. The method according to claim 6, wherein the metal nanostructure is a rectangle with a length of 150-250 nm, a width of 50-100 nm, and a thickness of 30-60 nm.
8. The method of manipulating optical spin angular momentum of claim 6, wherein the material of the metal nanostructure is gold, silver or aluminum.
9. The method of manipulating optical spin angular momentum of claim 6, wherein the metallic nanostructures are fabricated on an insulating substrate.
10. A method of using photon spin as an information carrier, performing photon spin coding based on the method of manipulating optical spin angular momentum of claim 6, defining a far field angle-resolved pattern of a left-handed circularly polarized component radiation direction in a left hemisphere and a right-handed circularly polarized component radiation direction in a right hemisphere as "0"; a far field angle resolution mode that the radiation direction of the left-handed circular polarization component is positioned in the right hemisphere and the radiation direction of the right-handed circular polarization component is positioned in the left hemisphere is defined as '1'; defining a far field angle resolution mode with the left and right circular polarization component radiation directions not separated as an erasure code; the three modes of '0', '1' and the erasing code respectively correspond to the electron beam bombardment sites which are positioned at the middle point of the upper edge, the middle point of the lower edge and the central position of the rectangle of the long edge of the rectangular metal nano structure; by designing the scanning path of the electron beam, the output of different coded information is realized.
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