High-resolution broadband terahertz detector based on pixelized structure and detection method
阅读说明：本技术 基于像素化结构的高分辨率宽带太赫兹探测器和探测方法 (High-resolution broadband terahertz detector based on pixelized structure and detection method ) 是由 王日德 常超 孙郎 王佳艺 焦亚楠 马兆福 娄菁 乔智 于 2021-08-23 设计创作，主要内容包括：本发明提供了一种基于像素化结构的高分辨率宽带太赫兹探测器和探测方法,涉及太赫兹物质检测,包括：由太赫兹波高透过率材料制成的基底；像素化超表面阵列结构,设于基底上,超表面阵列结构包括多种尺寸的谐振单元,以便于扩宽响应的光谱范围；介电材料,设于像素化超表面阵列结构与基底之间,介电材料的介电属性能够被调节,以影响谐振单元的共振响应,使得谐振单元的谐振频率发生频移；每一种尺寸的谐振单元的阵列组成一个探测区,探测区中的谐振单元与介电材料组成的结构形成元像素。本发明公开的技术方案能够对未知分析物质的多特征指纹吸收谱进行宽带检测,并实现了器件的高集成和小型化。(The invention provides a high-resolution broadband terahertz detector based on a pixelized structure and a detection method, which relate to terahertz substance detection and comprise the following steps: a substrate made of a terahertz wave high transmittance material; the pixelized super-surface array structure is arranged on the substrate and comprises resonance units with various sizes so as to widen the spectral range of response; the dielectric material is arranged between the pixilated super-surface array structure and the substrate, and the dielectric property of the dielectric material can be adjusted to influence the resonance response of the resonance unit so as to enable the resonance frequency of the resonance unit to be shifted; the array of resonant cells of each size constitutes a detection area, and the structure of resonant cells and dielectric material in the detection area forms a pixel. The technical scheme disclosed by the invention can carry out broadband detection on the multi-feature fingerprint absorption spectrum of an unknown analysis substance, and realizes high integration and miniaturization of devices.)
1. A high-resolution broadband terahertz detector based on a pixilated structure is characterized by comprising:
a substrate made of a terahertz wave highly transparent material;
a pixelated super-surface array structure disposed on the substrate, the super-surface array structure comprising resonant cells of various sizes so as to broaden the spectral range of the response;
a dielectric material disposed between the pixelated super surface array structure and the substrate, a dielectric property of the dielectric material being adjustable to affect a resonant response of the resonant unit such that a resonant frequency of the resonant unit is shifted;
the array of the resonance units with each size forms a detection area, the dielectric material is arranged on the lower side of the detection area, the resonance units and the structure formed by the dielectric material in the detection area form element pixels, the arrays of the resonance units with various sizes form a plurality of detection areas, and the detection areas and the dielectric material form a plurality of element pixels, so that the pixelated super-surface array structure supports the broadband terahertz wave spectral response.
2. The pixelated structure-based high-resolution broadband terahertz detector of claim 1, wherein a spectral response range of the detector is determined according to various sizes and/or layout forms of constituent elements of the resonance unit.
3. The pixelated structure-based high-resolution broadband terahertz detector according to claim 2, wherein the resonance unit comprises two symmetrically arranged open resonance rings, a distance is reserved between the rings, the openings are far away from each other to support a ring dipole mode, and the dielectric material is arranged at the openings of the resonance rings.
4. The pixelated structure-based high-resolution broadband terahertz detector of claim 2, wherein the material of the resonant ring is any one of gold, silver or aluminum, and the radius of the resonant ring is adjusted so as to spectrally cover a range of target analyte fingerprint spectra.
5. The pixelated structure-based high-resolution broadband terahertz detector according to any one of claims 1 to 4, wherein the dielectric material is graphene, and the manner of adjusting the dielectric property of the dielectric material specifically comprises: the Fermi level of the material is changed by adjusting the potential difference applied across the graphene.
6. A substance detection method for the pixilated structure based high resolution broadband terahertz detector according to any one of claims 1 to 5, comprising:
the method comprises the steps of testing and recording spectral lines of element pixels with various sizes through a terahertz time-domain spectroscopy system, continuously adjusting the dielectric property of a dielectric material, and recording the spectral line of a super-surface structure after each adjustment;
transferring the object to be tested to the super-surface structure, testing the spectral lines of the element pixels with various sizes again, continuously adjusting the dielectric property of the dielectric material, and recording the spectral line of the super-surface structure after each adjustment;
qualitatively analyzing the object to be detected by comparing the change of the spectral information before and after the object to be detected is placed;
the array of the resonance units with a certain size and the corresponding dielectric material form element pixels of the detector, after the element pixels are moved into an object to be detected, the obvious change of reflection and transmission spectrums of the element pixels is expressed as attenuation and broadening of an envelope curve of resonance peaks of the element pixels, and the object to be detected is a single substance or a mixed substance.
7. The method of claim 6, wherein the radius of the resonant cells supports individual adjustments to purposefully spectrally cover a fingerprint spectral range of a target analyte.
8. The substance detection method according to claim 6, wherein adjusting the dielectric properties of the dielectric material specifically comprises:
and adjusting the Fermi level of the graphene material.
9. A substance detection device, comprising: a terahertz time-domain spectroscopy system and the pixelated structure-based high-resolution broadband terahertz detector of any one of claims 1 to 5 configured to receive terahertz pulses of the terahertz time-domain spectroscopy system.
Technical Field
The invention relates to the technical field of terahertz substance detection, in particular to a high-resolution broadband terahertz detector based on a pixilated structure and a detection method.
Background
The terahertz wave is positioned between a millimeter wave band and an infrared wave band, and has the characteristics of photonics and electronics. Terahertz waves have the characteristics of non-ionization, no damage, high penetration, high resolution, spectral fingerprints and the like, so that the terahertz waves become potential tools in the field of biomedicine. Recently, due to the rapid development of terahertz fingerprint detection of biochemical analytes, terahertz sensing has become a promising technology in biomedical research and substance detection. However, due to the lack of a terahertz source with high radiation intensity and the mismatch between the wavelength of the terahertz wave and the size of the analyte, the wide application of terahertz in substance detection is seriously affected. In carrying out the present invention, the applicant has found that: the micro-nano photonics breaks the limitation by utilizing the strong near-field enhancement effect of a sub-wavelength resonance structure, the sub-wavelength resonance structure can control the polarization, the phase, the amplitude and the like of light, and can be used for light emission, detection, modulation, control and amplification of micro-nano scale; near-field enhancement of the optical field at the microstructure can promote interaction of light with matter; the resonance peak position of the structure is overlapped with the characteristic fingerprint spectrum of the substance to be analyzed by designing and adjusting the structural parameters, so that the near field enhancement is utilized to qualitatively identify the analyte, but the requirements of the method on the structural design and the experimental operation precision are very strict.
The existing design and experimental scheme has the following problems: firstly, detecting by designing a single microstructure to overlap the resonance peak position thereof with a single fingerprint of an analyte; the response of the microstructure is designed according to a certain characteristic fingerprint spectrum known by an analyte, so that the wide application of the detector in practice is severely limited; the resonance response of the microstructure has strong dependency on the refractive index change of the environment medium, so that the thickness and the density of an analyte can directly influence the response of the microstructure, and the resonance peak position and the fingerprint spectrum are overlapped very difficultly in experimental operation; in addition, because the single peak position is used for detection, the method can be only used for detecting one target object; if more substances are required to be detected, the structural parameters of the sensor can be changed, more sensors are processed, and therefore the efficiency is low; secondly, the Hatice Altug topic group provides an expansion method for the sensing detection of the wide-spectrum characteristic absorption fingerprint spectrum, and can be more widely applied to complex biological tests; however, because the spectrum and the spatial information present a one-to-one correspondence relationship, when the spectrum information to be measured is wide, the size of the sensor is inevitably large, which is not beneficial to the design and research of flexible, convenient, small-sized and high-integration devices; thirdly, the broadband spectrum obtained by tuning the structural parameters has lower resolution, which seriously affects the accurate measurement of the device on the characteristic absorption peak of the analyte.
Disclosure of Invention
The invention aims to at least solve one of the technical problems in the prior art or the related art, and discloses a high-resolution broadband terahertz detector and a detection method based on a pixilated structure, which can perform broadband detection on a multi-feature fingerprint spectrum of an unknown substance, realize the high integration and miniaturization of a device and improve the detection precision.
The invention discloses a high-resolution broadband terahertz detector based on a pixelized structure, which comprises: a substrate made of a terahertz wave high transmittance material; the pixelized super-surface array structure is arranged on the substrate and comprises resonance units with various sizes so as to widen the spectral range of response; the dielectric material is arranged between the pixelized super-surface array structure and the substrate, the dielectric property of the dielectric material can be adjusted to influence the resonance response of the resonance units, so that the resonance frequency of the resonance units is subjected to frequency shift, wherein the array of the resonance units with each size forms a detection area, the dielectric material is arranged on the lower side of the detection area, the structure formed by the resonance units and the dielectric material in the detection area is an element pixel, a plurality of arrays of the resonance units with various sizes form a plurality of detection areas, and the plurality of detection areas and the dielectric material form a plurality of element pixels, so that the pixelized super-surface array structure supports the terahertz wave spectral response of a wide frequency band.
In the technical scheme, the high-resolution broadband terahertz fingerprint spectrum detector based on the pixelization structure overcomes the defect that the existing detector can only be used for detecting one target object, is convenient to widely apply, and has high tolerance on the thickness and the density of an analyte and high detection efficiency. Compared with the existing detector, the detector has smaller volume when measuring wider spectral information, and is more convenient to flexibly and conveniently deploy. In order to miniaturize the sensor device as much as possible, a dielectric material is introduced at the resonant cell gap, and the adjustment of the microstructure characteristic response is realized by adjusting the dielectric property. The tunable design realizes that one unit structure responds to a plurality of spectral lines, and improves the current situation that the step length of the moving response spectral line depends only on the size change of the structure. The electromagnetic response characteristic of the super-surface unit structure is adjusted by changing the property of the dielectric material, and compared with the adjustment of the structural parameters of the super-surface, the resolution is higher, and the wide-spectrum and accurate detection is carried out on the multi-fingerprint spectrum of the substance. The pixelization structure is a core design for realizing wide-spectrum fingerprint detection, and the unit structure arrays with different sizes form a regionalization structure to obtain response with larger step length. The dielectric material is configured to enable adjustment of the dielectric properties, the accuracy of which determines the resolution of the detector, thereby achieving a higher resolution.
According to the high-resolution broadband terahertz detector based on the pixelized structure, preferably, the resonance unit specifically comprises a plurality of resonance rings, and the spectral response range of the detector is determined according to different sizes and/or layout forms of the resonance rings.
According to the high-resolution broadband terahertz detector based on the pixelized structure disclosed by the invention, preferably, the resonance unit specifically comprises two symmetrically arranged open resonance rings, a distance is reserved between the rings, the openings are far away from each other to support an annular dipole mode, and a dielectric material is arranged at the opening of each resonance ring.
In the technical scheme, the structure of the symmetrical open resonant ring is used as a unit, a ring dipole mode is introduced, the mode is coupled with a free space very weakly, the radiation loss of the structure is reduced well, and the micro-structure unit design with high quality factors is realized.
According to the high-resolution broadband terahertz detector based on the pixelized structure, preferably, the material of the resonance ring is gold, silver or aluminum, and the radius of the resonance ring can be adjusted so as to cover the range of the target analyte on the spectrum.
According to the high-resolution broadband terahertz detector based on the pixelated structure disclosed by the invention, preferably, the dielectric material is graphene, and the method for adjusting the dielectric property of the dielectric material specifically comprises the following steps: and adjusting the Fermi level of the graphene material.
In the technical scheme, in order to miniaturize the sensor device as much as possible, graphene is introduced into the gap of the open resonant ring, the adjustment of the microstructure characteristic response is realized by adjusting the Fermi level of the graphene, the resolution of the detector is determined by the adjustment precision, and the resolution is obviously higher than that of the traditional detector.
According to the high-resolution broadband terahertz detector based on the pixilated structure, the substrate is preferably a quartz substrate.
In the technical scheme, materials which are similar to quartz and have high transmittance property to terahertz waves can be used as substrates.
The second aspect of the present invention discloses a substance detection method for a high-resolution broadband terahertz detector based on a pixelized structure as disclosed in any one of the above technical solutions, comprising: the method comprises the steps of testing and recording spectral lines of element pixels with various sizes through a terahertz time-domain spectroscopy system, continuously adjusting the dielectric property of a dielectric material, and recording the spectral line of a super-surface structure after each adjustment; transferring the object to be tested to the super-surface structure, testing the spectral lines of the element pixels with various sizes again, continuously adjusting the dielectric property of the dielectric material, and recording the spectral line of the super-surface structure after each adjustment; qualitatively analyzing the object to be detected by comparing the change of the spectral information before and after the object to be detected is placed; after the array of the resonance units with a certain size and the corresponding dielectric material form the element pixel of the detector, the obvious change of the reflection and transmission spectrums of the element pixel is expressed as the attenuation and the broadening of the envelope curve of the resonance peak of the element pixel after the element pixel is moved into an object to be detected, and the object to be detected is a single substance or a mixed substance.
According to the method for detecting a substance disclosed in the above technical solution of the present invention, preferably, the radius of the resonance unit supports individual adjustment to purposefully spectrally cover the fingerprint spectrum range of the target analyte.
According to the substance detection method disclosed in the above technical solution of the present invention, preferably, the adjusting the dielectric property of the dielectric material specifically includes: and adjusting the Fermi level of the graphene material.
The third aspect of the present invention also discloses a substance detecting apparatus comprising: the terahertz time-domain spectroscopy system and the high-resolution broadband terahertz detector based on the pixelized structure disclosed in any one of the above technical solutions are provided, wherein the high-resolution broadband terahertz detector based on the pixelized structure is configured to receive terahertz pulses of the terahertz time-domain spectroscopy system.
The beneficial effects of the invention at least comprise:
(1) forming a pixilated super surface by laying out elementary pixels consisting of different sized cell array structures and functional materials (dielectric materials); response spectral lines with large step length are obtained among different element pixels, a wide terahertz frequency spectrum is covered, and wide-spectrum fingerprint spectrum detection is achieved.
(2) By adjusting the dielectric property of the functional material and adjusting the characteristic response of the microstructure, the resonance frequency of the unit structure is shifted, so that the unit structure corresponds to a plurality of spectral lines. The sensor size is reduced to a large extent by the design, the miniaturization and high integration of devices are realized, and the detection resolution is improved.
(3) The interaction of light with matter is enhanced by means of a circular dipole mode supported by a symmetrically split resonant ring. The coupling of the annular dipole mode and the free space is very weak, so that the radiation loss of the structure is well reduced, and the high-sensitivity detection of substances can be realized.
Drawings
Fig. 1 shows a schematic top-view structure of a high-resolution broadband terahertz detector based on a pixelated structure according to an embodiment of the invention.
Fig. 2 shows a schematic side view of a high-resolution broadband terahertz detector based on a pixelated structure according to one embodiment of the invention.
Fig. 3 shows a schematic diagram of a resonant ring structure of a pixelized structure based high resolution broadband terahertz detector according to an embodiment of the invention.
FIG. 4 shows a schematic view of a substance detection device according to an embodiment of the present invention.
FIG. 5 shows a broad spectral signature fingerprint absorption spectrum of glucose, according to one embodiment of the invention.
In the figure: the terahertz detection device comprises an open resonant ring 1, a dielectric material 2, a quartz substrate 3, an electrode 4, a pixilated detector 5, a detected substance 6, a femtosecond laser 7, a beam splitter 8, a first reflector 9, a delay line 10, a second reflector 11, a terahertz generator 12, a first parabolic mirror 13, a semi-transparent semi-reflective mirror 14, a second parabolic mirror 15, a sample 16, a two-dimensional translation sample stage 17, a third parabolic mirror 18, a dichroic mirror 19, a third reflector 20, a terahertz sensor 21, a lock-in amplifier 22 and a computer 23.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments disclosed below.
As shown in fig. 1 and fig. 2, according to an embodiment of the present invention, a high-resolution broadband terahertz fingerprint spectrum detector 5 (hereinafter referred to as a pixelated detector 5) based on a pixelated structure is disclosed, including: an open resonant ring 1, a dielectric material 2, a quartz substrate 3 and an electrode 4; a dielectric material disposed between the split resonant ring and the quartz substrate, the dielectric material configured to have an adjustable dielectric property to affect a resonant response of the resonant unit such that a resonant frequency of the resonant unit is shifted; the array of the resonant rings with each size forms a detection area, the lower side of the detection area is provided with a dielectric material, and the structure formed by the resonant rings and the dielectric material in the detection area is an element pixel. The plurality of detection regions and the dielectric material form a plurality of element pixels, so that a pixilated super-surface array structure is formed. Wherein the size and/or layout of the resonant rings can determine the spectral range of the response.
According to the above embodiment, preferably, the split ring resonators are symmetrically arranged with a space between the rings, the split rings are spaced apart from each other to support a ring dipole mode, and the split rings are provided with a dielectric material.
According to the above embodiment, preferably, the material of the resonance ring is any one of gold, silver or aluminum, and the radius of the resonance ring can be adjusted so as to spectrally cover the range of the target analyte fingerprint spectrum.
According to the above embodiment, preferably, the dielectric material is graphene, and the method for adjusting the dielectric property of the dielectric material specifically includes: and adjusting the Fermi level of the graphene material.
h denotes the thickness of the quartz substrate, and the substance to be detected 6 is placed on the surface of the pixelated detector 5. The cell structure of a pixelized super-surface array is shown in FIG. 3, R1、R2The radius of the inner ring and the radius of the outer ring of the resonance ring are respectively; w is the distance between the two resonance rings; theta is a central angle corresponding to the opening of the single resonance ring; p1And P2The periods of the short side and the long side of the unit structure are respectively.
There is also disclosed, in accordance with an embodiment of the present invention, a substance detecting device, including: a terahertz time-domain spectroscopy system and a high-resolution broadband terahertz detector 5 based on a pixelated structure as disclosed in any one of the above embodiments, wherein the high-resolution broadband terahertz detector 5 based on the pixelated structure is configured to receive terahertz pulses of the terahertz time-domain spectroscopy system. As shown in fig. 4 in detail, the substance detecting apparatus includes: the terahertz detector comprises a femtosecond laser 7, a beam splitter 8, a first reflector 9, a delay line 10, a second reflector 11, a terahertz generator 12, a first parabolic mirror 13, a half-mirror 14, a second parabolic mirror 15, a sample 16 (composed of a substance 6 to be detected carried by the pixelated detector 5 disclosed in the above embodiment), a two-dimensional translation sample stage 17, a third parabolic mirror 18, a dichroic mirror 19, a third reflector 20, a terahertz sensor 21, a lock-in amplifier 22 and a computer 23. The substance detection process comprises: the femtosecond laser 7 emits femtosecond laser pulses, the femtosecond laser pulses are divided into pumping light and detection light after passing through the beam splitter 8, the pumping light passes through the delay line 10 and then is incident to the terahertz generator 12 to be excited to generate terahertz pulses, and the detection light and the terahertz pulses are incident to the terahertz sensor 21 in a collinear mode. The time delay between the pumping light and the detection light is adjusted by controlling the time delay system, and finally the reflection response spectral line before and after the substance to be detected is placed can be obtained. And the object to be detected can be qualitatively detected through spectral line comparison.
As shown in fig. 5, which shows the broad spectrum characteristic fingerprint absorption spectra of glucose with and without a pixelated super-surface structure, it can be seen that the pixelated super-surface significantly enhances the absorption of a substance from a broad spectrum by enhancing the light-substance interaction. Therefore, high-resolution broadband terahertz fingerprint spectrum detection based on the pixilated structure is realized.
According to an embodiment of the present invention, a substance detection method is disclosed for a high-resolution broadband terahertz detector based on a pixelated structure as disclosed in any of the above embodiments, the method comprising:
simulating the resonance spectral lines of the resonance units with different sizes by numerical values to enable the response to cover a wider spectral range on the spectrum as much as possible;
designing a pixelated super-surface layout, integrating a dielectric material and a superstructure on a substrate, and manufacturing a pixelated detector 5 disclosed in the above embodiment;
the method comprises the steps of testing and recording spectral lines of element pixels with various sizes through a terahertz time-domain spectroscopy system, continuously adjusting the dielectric property of a dielectric material, and recording the spectral line of a super-surface structure after each adjustment;
transferring the object to be tested to the super-surface structure, testing the spectral lines of the element pixels with various sizes again, continuously adjusting the dielectric property of the dielectric material, and recording the spectral line of the super-surface structure after each adjustment;
qualitatively analyzing the object to be detected by comparing the change of the spectral information before and after the object to be detected is placed; after the array of the resonance units with a certain size and the corresponding dielectric material form the element pixel of the detector, the obvious change of the reflection and transmission spectrums of the element pixel is expressed as the attenuation and the broadening of the envelope curve of the resonance peak of the element pixel after the element pixel is moved into an object to be detected, and the object to be detected is a single substance or a mixed substance.
In this embodiment, the broad spectral range is largely determined by two factors: firstly, the sizes of different split ring resonators can obtain response with larger step length; secondly, the property of the functional material is adjusted so as to influence the resonance response of the structural unit and change the spectral line within a certain range. The high resolution characteristics depend on the precision with which the functional material is adjusted. The pixelized super-surface is composed of different regions of meta-pixels, the meta-pixels are formed by periodic unit structures of a certain fixed size, and the different meta-pixels are composed of unit structures of different sizes. By the method, multiple characteristic spectral lines of a single substance or multiple mixed substances can be accurately detected, and the problem that false positive can be caused when the substance is distinguished through a single characteristic absorption spectral line is optimized. The detection resolution is improved by changing the access voltage of the dielectric material, and the miniaturization of the device and the high-sensitivity wide-range multi-fingerprint detection of substances are realized.
According to the substance detection method disclosed in the above embodiment of the present invention, preferably, the radii of the unit structures support individual adjustment to purposefully spectrally cover the range of the target analyte fingerprint spectrum.
According to the substance detection method disclosed in the above embodiment of the present invention, preferably, the method of adjusting the dielectric property of the dielectric material specifically includes: and adjusting the Fermi level of the graphene material.
According to the above embodiments of the present invention, the present invention forms a pixelated super-surface by laying out the element pixels composed of different sized cell array structures and functional materials (dielectric materials); response spectral lines with large step length are obtained among different element pixels, a wide terahertz frequency spectrum is covered, and wide-spectrum fingerprint spectrum detection is achieved. By adjusting the dielectric property of the functional material and adjusting the characteristic response of the microstructure, the resonance frequency of the unit structure is shifted, so that the unit structure corresponds to a plurality of spectral lines. The sensor size is reduced to a large extent by the design, the miniaturization and high integration of devices are realized, and the detection resolution is improved. The interaction of light with matter is enhanced by means of a circular dipole mode supported by a symmetrically split resonant ring. The coupling of the annular dipole mode and the free space is very weak, so that the radiation loss of the structure is well reduced, and the high-sensitivity detection of substances can be realized.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.