An ultra-surface spectrometer for regulating wave vector space and a preparation method thereof

Abstract

The present application relates to the field of spectral technology, and specifically provides a kind of super surface spectrometer of wave vector space regulation and preparation method thereof, based on the principle of light field phase mutation, sharp wave vector peak will be generated at light intensity zero point, the position coordinates of light intensity zero point in field of view are regulated to make wave vector peak linearly move with incident wavelength, the spectrum resolution is transferred from time domain space to wave vector space, the generation of off-axis aberration is avoided, effectively solve the problem of spectrum resolution decline rate caused by spectral feature peak broadening.Due to the parallelism between the detection plane of the spectral system and the plane of the super surface element, the integration of the spectral system is further improved. By limiting the zero light intensity, the phase mutation degree is improved, the full width at half maximum of the wave vector space spectrum recognition peak is reduced, and the spectral resolution is further improved to sub-nanometer level.

Description

Technical Field

[0001] This invention relates to the field of spectroscopy, specifically providing a metasurface spectrometer for controlling wave vector space and its preparation method. Background Technology

[0002] Spectroscopic technology is widely used in fields such as celestial detection, materials science, biotechnology, and medical diagnostics. To ensure high resolution, traditional spectroscopic systems often require multiple components to achieve spectral resolution, resulting in complex systems that are large in size and difficult to integrate, failing to simultaneously meet the requirements for portability and high precision.

[0003] With the development of modern micro-nano manufacturing processes, metasurfaces, a type of customized "artificial electromagnetic metamaterial," have emerged. As a two-dimensional plane composed of subwavelength-sized unit structures, metasurfaces can achieve wavefront manipulation within a thickness smaller than the wavelength of light. They possess ultra-thin, ultra-light, and ultra-integrated characteristics, and can be used to replace bulky optical components in traditional spectral systems, enabling the integration of spectral systems.

[0004] Current dispersive metasurface spectrometers rely on the principle of dispersion to achieve spatial separation of spectral characteristic peaks. Their main drawback is that the metasurface spectral elements are affected by chromatic aberration when focusing on curved surfaces. This off-axis aberration causes broadening of spectral characteristic peaks, reducing spectral resolution. To minimize the impact of off-axis aberration on resolution, the detector plane is tilted by calculating its position. However, this operation affects the integration density of the spectroscopic system. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a metasurface spectrometer with adjustable wave vector space and its fabrication method, which can further improve spectral resolution and eliminate the need for calculation to determine the position of the detection plane, thereby increasing the system's integration.

[0006] This invention provides a method for preparing a metasurface spectrometer with modulated wave vector space, specifically including:

[0007] The metasurface element is designed using an optimization algorithm so that it generates a specific light field under the excitation of a plane wave. The linearity of the number of zero-intensity points, zero-intensity energy, and zero-intensity position curves of the specific light field with respect to wavelength displacement is restricted within a specified field of view.

[0008] The specific light field generated by the metasurface element at different wavelengths has one and only one pair of zero light intensity positions within the specified field of view, and the zero light intensity positions move linearly with the wavelength;

[0009] The number of phase abrupt change points is limited by controlling the number of zeros in the specific light field within the specified field of view, so that the corresponding wave vector space has one and only one pair of spectral characteristic peaks.

[0010] By using the energy that restricts the zero point position of the light field, the phase of the zero point position of the light field oscillates violently, generating an extremely narrow wave vector peak for spectral identification. The extremely narrow wave vector peak is used as a spectral characteristic peak and shifts with wavelength.

[0011] The metasurface element generates a super-resolution optical field. By determining the gradient of the phase of the super-resolution optical field, the wave vector curve of the super-resolution optical field is obtained, thus completing the conversion of the spectral characteristic peak from the time domain to the wave vector space.

[0012] As a preferred embodiment, the step of obtaining the wave vector curve of the super-resolution optical field by determining the gradient of the phase of the super-resolution optical field, thereby completing the transformation of the spectral characteristic peaks from the time domain to the wave vector space, includes:

[0013] The spectral characteristic peaks in wave vector space are obtained by using optical field phase inversion technology. The optical field distribution generated after left-handed, right-handed, and ±45° linearly polarized light is incident on the metasurface element is measured. The phase distribution of the pre-designed optical field is obtained by inversion calculation, and the wave vector curve distribution at the corresponding wavelength is obtained by calculating the phase gradient. The spectral identification peaks in the time domain space are converted to the wave vector space.

[0014] As a preferred embodiment, the method of designing metasurface elements using optimization algorithms to generate a specific light field under plane wave excitation, and limiting the linearity of the number of zero-intensity points, zero-intensity energy, and zero-intensity position curves of the specific light field with respect to wavelength displacement within a specified field of view, includes:

[0015] A 40×40μm metasurface element was optimized in the 793nm-820nm wavelength range. The element phase follows a 0 / π distribution. A specific light field is generated at the focal plane at 10μm. The optimization constraints are as follows: the light intensity at the origin x=0 is globally maximum; the second zero point of the specific light field is outside the specified field of view range of 2 times the diffraction limit; the light intensity at the zero point of the specified field of view range is <3×10^(-4); and the displacement Δx generated by the wave vector curve peak at different wavelengths is >0. The evaluation function for optimization is set as the standard deviation of the wave vector peak displacement curve with wavelength and the first self-fit function of the wave vector peak. The optimal solution of the phase distribution of the metasurface element is obtained by using a genetic algorithm.

[0016] The present invention also provides a metasurface spectrometer for controlling wave vector space, which is prepared according to the above-described method for preparing a metasurface spectrometer for controlling wave vector space.

[0017] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0018] This invention provides a metasurface spectrometer and its fabrication method for controlling wave vector space. Based on the principle of phase abrupt change in the optical field, a sharp wave vector peak is generated at the zero-intensity point. By controlling the position coordinates of the zero-intensity point within the field of view, the wave vector peak is linearly shifted with the incident wavelength, thus converting the spectral resolution from the temporal domain to the wave vector space. This avoids off-axis aberrations and effectively solves the problem of spectral resolution degradation caused by the broadening of spectral characteristic peaks. Since the detection plane of the spectral system is parallel to the plane of the metasurface element, the integration of the spectral system is further improved. By limiting the zero-intensity light, the degree of phase abrupt change is increased, the full width at half maximum (FWHM) of the wave vector space spectral recognition peak is reduced, and the spectral resolution is further improved to the sub-nanometer level. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of a method for preparing a metasurface spectrometer with adjustable wave vector space according to an embodiment of the present invention;

[0020] Figure 2 This is a phase distribution diagram of the metasurface element in the method for preparing a metasurface spectrometer with adjustable wave vector space provided in an embodiment of the present invention;

[0021] Figure 3 This is a light field intensity diagram of the y-direction under different polarization states with an incident wavelength of 800 nm in the method for preparing a metasurface spectrometer with controlled wave vector space provided in the embodiment of the present invention;

[0022] Figure 4 This is an inversion phase diagram with an incident wavelength of 800 nm in the method for preparing a metasurface spectrometer with controlled wave vector space provided in an embodiment of the present invention;

[0023] Figure 5 This is a wave vector distribution diagram at an incident wavelength of 800 nm in the method for preparing a metasurface spectrometer with adjustable wave vector space provided in an embodiment of the present invention;

[0024] Figure 6 This is a wave vector distribution curve of 793nm:2nm:819nm in the method for preparing a metasurface spectrometer with adjustable wave vector space provided in the embodiment of the present invention;

[0025] Figure 7 This is a resolution distribution map of 793nm-820nm in the metasurface spectrometer preparation method for controlling wave vector space provided in the embodiment of the present invention. Detailed Implementation

[0026] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0028] Combination Figure 1 As shown, this embodiment of the invention provides a method for preparing a metasurface spectrometer with adjustable wave vector space, specifically including:

[0029] S101. Design a metasurface element using an optimization algorithm, so that the metasurface element generates a specific light field under the excitation of a plane wave, and limit the linearity of the number of zero-intensity points, zero-intensity energy, and zero-intensity position curves of the specific light field with respect to wavelength displacement within a specified field of view.

[0030] S102. Adjust the specific light field generated by the metasurface element at different wavelengths so that there is one and only one pair of zero light intensity positions within the specified field of view, and the zero light intensity positions move linearly with the wavelength.

[0031] S103. Based on controlling the number of zeros in the specified field of view of the specific light field, the number of phase transition points is limited, so that the corresponding wave vector space has one and only one pair of spectral characteristic peaks.

[0032] S104. Using the energy that restricts the zero point position of the light field, the phase of the zero point position of the light field oscillates violently, generating an extremely narrow wave vector peak for spectral identification. The extremely narrow wave vector peak is used as a spectral characteristic peak and shifts with wavelength.

[0033] S105. The metasurface element generates a super-resolution optical field. By determining the gradient of the phase of the super-resolution optical field, the wave vector curve of the super-resolution optical field is obtained, thus completing the conversion of the spectral characteristic peak from the time domain to the wave vector space.

[0034] The method for fabricating a metasurface spectrometer based on wave vector space provided in this invention employs wave vector space-based spectral resolution technology, solving the problem that the resolution of spectrometers based on the dispersion principle is limited by chromatic aberration. It utilizes the sharp wave vector curve generated by rapid phase oscillation at the zero point of the light field to convert the spectral identification peak in the time domain to the wave vector space. By designing metasurface elements using optimization algorithms and controlling the position of the zero point of the light field at different wavelengths, the spectral identification peak in the wave vector space shifts linearly with wavelength. The non-dispersive spectral resolution technology avoids the influence of chromatic aberration on spectral characteristic peaks. The extremely narrow wave vector peaks at the sub-nanometer level can further improve spectral resolution, and the position of the detection plane does not need to be determined by calculation, thus improving the system's integration.

[0035] In step S105, the wave vector curve of the super-resolution light field is obtained by determining the gradient of the phase of the light field, thus completing the transformation of the spectral characteristic peaks from the time domain to the wave vector space. Specifically, this includes:

[0036] Combination Figure 2 As shown, the spectral characteristic peaks in wave vector space are obtained using optical field phase inversion technology. The optical field distributions generated after left-handed, right-handed, and ±45° linearly polarized light are incident on the metasurface element are measured respectively. The phase distribution of the pre-designed optical field is obtained through inversion calculation. The phase distribution diagram is shown in the figure. Figure 2 As shown, the phase gradient is calculated to obtain the wave vector curve distribution at the corresponding wavelength, and the spectral identification peak in the time domain space is transformed into the wave vector space. This non-dispersive spectral resolution technology avoids the generation of off-axis aberrations and effectively solves the problem of spectral resolution reduction caused by the broadening of spectral characteristic peaks. Its detection plane is parallel to the element, ensuring the high integration of the spectral system.

[0037] In one embodiment, S101 includes:

[0038] The optimization algorithm employs a genetic algorithm to optimize a 40×40μm metasurface element in the 793nm-820nm wavelength range. The element's phase follows a 0 / π distribution, and a specific light field is generated at the focal plane at 10μm. The optimization constraints are as follows: the light intensity at the origin x=0 is globally maximized; the second zero point of the specific light field is located outside the specified field of view range of 2 times the diffraction limit; the light intensity at the zero point within the specified field of view range is <3×10^(-4); and the displacement Δx generated by the wave vector curve peak at different wavelengths is >0. The evaluation function for optimization is set as the standard deviation of the wave vector peak displacement curve with wavelength and the first-order self-fit function of the wave vector peak. The optimal solution for the phase distribution of the metasurface element is obtained by using a genetic algorithm.

[0039] The light field generated by incident wavelengths of 793nm-820nm has only one pair of zero-intensity points within the field of view at twice the diffraction limit, and the light intensity is <3×10^(-4). The coordinates of the zero points shift along the positive x-axis with increasing wavelength. To obtain the wave vector curve of the light field and use it as a characteristic peak for spectral identification, the phase distribution of the light field needs to be obtained, and the wave vector distribution is obtained through gradient calculation. Since the phase distribution of the light field cannot be directly obtained by measurement, the light field distribution generated by left-handed, right-handed, and ±45° linearly polarized light incident on the metasurface was measured respectively. The phase distribution of the pre-designed light field was obtained through phase inversion calculation, and the phase gradient was calculated to obtain the wave vector curve distribution at the corresponding wavelength. The phase gradient peak shifts linearly along the positive x-axis in the range of 793nm-820nm, and the spectral resolution within the bandwidth is less than 2.1nm. Sub-nanometer spectral resolution can be achieved at 9 wavelengths, with the optimal resolution of 0.37nm generated at 794nm and 816nm.

[0040] Light fields with different polarization states undergo cross-polarization after passing through the metasurface. Therefore, when x-polarized light is incident, the light field used for spectral resolution is generated in the y-direction, while a plane wave is generated in the x-direction as a reference light field. Since the phase distribution of this light field cannot be directly obtained through measurement, the intensity distribution of the light field in the y-direction is obtained by incident light fields with different polarization states on the metasurface.

[0041]

[0042]

[0043] Phase of the required light field Reference light field phase

[0044] Based on the light intensity distribution under different polarization states, the phase inversion formula is obtained:

[0045]

[0046] Combination Figure 3 As shown, when the incident wavelength is 800 nm, different polarization states (left-handed, right-handed, ±45°) are used to incident on the metasurface element. Figure 3 The figure shows the light field intensity of the metasurface element in the y direction. The light field excited by the metasurface in the x direction polarized incident direction is the design light field, and the diffraction limit r0 = 0.5λ / NA.

[0047] Combination Figure 4 As shown, based on the light intensity distribution in the y-direction under different polarization states of left-handed, right-handed, and ±45°, the phase distribution of the designed light field is obtained by inversion, and a phase abrupt change close to π is generated at the zero light intensity position.

[0048] Combination Figure 5 As shown, the wave vector distribution is calculated using the phase distribution obtained from the inversion. Figure 5 The diagram shows the wave vector distribution at an incident wavelength of 800 nm. Due to the abrupt change in phase at the zero intensity point, the wave vector... As the phase gradient increases sharply in the x-direction and then decreases sharply, it produces an extremely narrow peak at zero, with a full width at half maximum (FWHM) of only 8 nm.

[0049] Combination Figure 6 As shown, the spectral characteristic peaks in the time domain are transformed to the wave vector space. Figure 6 The graph shows the wave vector distribution curves at 793nm:2nm:819nm. Spectral identification is achieved using sharp wave vector peaks. The maximum and minimum full width at half maximum (FWHM) of the characteristic peaks within the bandwidth range are 3.1nm and 8.2nm, respectively.

[0050] Combination Figure 7As shown, the metasurface spectrometer based on wave vector space has a resolution distribution of 793nm-820nm. Its spectral resolution is less than 2.1nm, and it achieves sub-nanometer spectral resolution at 9 wavelengths. The optimal resolution at 794nm and 816nm is 0.37nm.

[0051] This invention utilizes an optimization algorithm to design metasurface elements that generate specific light fields under plane wave excitation. It imposes restrictions on the number of zero-intensity points, zero-intensity energy, and the linearity of the zero-intensity position shift curve with wavelength within a specified field of view. This ensures that the light fields generated by the metasurface elements at different wavelengths have exactly one pair of zero-intensity points within the specified field of view, with zero-intensity energy approximately zero and positions shifting linearly with wavelength. By controlling the number of zero-intensities within the field of view, the number of phase abrupt change points is limited, ensuring that the corresponding wave vector space has exactly one pair of spectral characteristic peaks, avoiding the introduction of other clutter peaks that could interfere with spectral identification. By limiting the energy at the zero-intensities, the phase at those locations oscillates violently, generating extremely narrow wave vector peaks for spectral identification, thus guaranteeing spectral resolution. Controlling the linearity of the zero-intensity coordinate shift curves at different wavelengths prevents spectral aliasing caused by the reverse shift of spectral identification peaks, which could affect spectral bandwidth and resolution. The wave vector curve of the light field is obtained by calculating the phase gradient, realizing the conversion of spectral characteristic peaks from the time domain to the wave vector space. Since the phase distribution of the light field cannot be directly obtained through measurement, this invention utilizes light field phase inversion technology to obtain the spectral characteristic peaks in the wave vector space. The light field distribution generated after left-handed, right-handed, and ±45° linearly polarized light is incident on the metasurface is measured respectively. The phase distribution of the pre-designed light field is obtained through inversion calculation, and the phase gradient is calculated to obtain the wave vector curve distribution at the corresponding wavelength. The spectral identification peaks in the time domain space are converted to the wave vector space. This non-dispersive spectral resolution technology avoids the generation of off-axis aberrations and effectively solves the problem of spectral resolution reduction caused by the broadening of spectral characteristic peaks. The detection plane of the metasurface spectrometer is parallel to the element, ensuring the high integration of the spectral system.

[0052] This invention also provides a metasurface spectrometer for controlling wave vector space, which is prepared according to the above-described method for preparing a metasurface spectrometer for controlling wave vector space.

[0053] This invention provides a metasurface spectrometer for controlling wave vector space. Based on the principle of phase abrupt change in the optical field, a sharp wave vector peak is generated at the zero-intensity point. By adjusting the position coordinates of the zero-intensity point within the field of view, the wave vector peak is linearly shifted with the incident wavelength, thus converting the spectral resolution from the temporal domain to the wave vector space. This avoids off-axis aberrations and effectively solves the problem of spectral resolution degradation caused by the broadening of spectral characteristic peaks. Since the detection plane of the spectral system is parallel to the plane of the metasurface element, the integration of the spectral system is further improved. By limiting the zero-intensity light, the degree of phase abrupt change is increased, reducing the full width at half maximum (FWHM) of the wave vector space spectral recognition peak, further improving the spectral resolution to the sub-nanometer level.

[0054] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0055] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a metasurface spectrometer with modulated wave vector space, characterized in that, include: The metasurface element is designed using an optimization algorithm so that it generates a specific light field under the excitation of a plane wave. The linearity of the number of zero-intensity points, zero-intensity energy, and zero-intensity position curves of the specific light field with respect to wavelength displacement is restricted within a specified field of view. The specific light field generated by the metasurface element at different wavelengths has one and only one pair of zero light intensity positions within the specified field of view, and the zero light intensity positions move linearly with the wavelength; The number of phase abrupt change points is limited by controlling the number of zeros in the specific light field within the specified field of view, so that the corresponding wave vector space has one and only one pair of spectral characteristic peaks. By using the energy that restricts the zero point position of the light field, the phase of the zero point position of the light field oscillates violently, generating an extremely narrow wave vector peak for spectral identification. The extremely narrow wave vector peak is used as a spectral characteristic peak and shifts with wavelength. The metasurface element generates a super-resolution optical field. By determining the gradient of the phase of the super-resolution optical field, the wave vector curve of the super-resolution optical field is obtained, thus completing the conversion of the spectral characteristic peak from the time domain to the wave vector space.

2. The method for preparing a metasurface spectrometer with adjustable wave vector space according to claim 1, characterized in that, The step of obtaining the wave vector curve of the super-resolution optical field by determining the gradient of the phase of the super-resolution optical field, and completing the transformation of the spectral characteristic peaks from the time domain to the wave vector space, includes: The spectral characteristic peaks in wave vector space are obtained by using optical field phase inversion technology. The optical field distribution generated after left-handed, right-handed, and ±45° linearly polarized light is incident on the metasurface element is measured. The phase distribution of the pre-designed optical field is obtained by inversion calculation, and the wave vector curve distribution at the corresponding wavelength is obtained by calculating the phase gradient. The spectral identification peaks in the time domain space are converted to the wave vector space.

3. The method for preparing a metasurface spectrometer with adjustable wave vector space according to claim 1, characterized in that, The method of designing metasurface elements using optimization algorithms to generate a specific light field under plane wave excitation, and limiting the linearity of the number of zero-intensity points, zero-intensity energy, and zero-intensity position curves of the specific light field with respect to wavelength displacement within a specified field of view, includes: A 40×40μm metasurface element was optimized in the 793nm-820nm wavelength range. The element phase follows a 0 / π distribution. A specific light field is generated at the focal plane at 10μm. The optimization constraints are as follows: the light intensity at the origin x=0 is globally maximum; the second zero point of the specific light field is outside the specified field of view range of 2 times the diffraction limit; the light intensity at the zero point of light intensity within the specified field of view range is <3×10^(-4); and the displacement Δx generated by the wave vector curve peak at different wavelengths is >0. The evaluation function for optimization is set as the standard deviation of the wave vector peak displacement curve with wavelength and the first self-fit function of the wave vector peak. The optimal solution of the phase distribution of the metasurface element is obtained by using a genetic algorithm.

4. A metasurface spectrometer for controlling wave vector space, characterized in that, It is prepared according to the method for preparing a metasurface spectrometer with controlled wave vector space as described in any one of claims 1 to 3.

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