CN111141385B - Narrow-band transmission filter and on-chip spectral analysis and imaging system - Google Patents
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/12—Generating the spectrum; Monochromators
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
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- G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
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Abstract
The invention discloses a narrow-band transmission filter and an on-chip spectral analysis and imaging system, wherein the filter comprises a substrate, a grating structure is firstly formed on the surface of the substrate, then a metal/metalloid film is deposited, or a metal/metalloid film is firstly deposited on the surface of the substrate, then a grating structure is formed, and the central wavelength of a band-pass is adjusted by changing the substrate material, the metal/metalloid material and the grating structure; the system comprises a filter array and a detector array, wherein the filter array is composed of a plurality of filter units with different band-pass center wavelengths, each filter unit adopts the narrow-band transmission filter, and the filter units of the filter array and the detector units of the detector array are combined in a one-to-one correspondence mode. The filter has large working wavelength bandwidth and narrow pass band, and the filters with different central wavelengths can be obtained by once graphic processing, and the on-chip spectral analysis and imaging system is formed by the filter and the detector array, so that the system performance is greatly improved, and the system complexity is reduced.
Description
Technical Field
The invention relates to a narrow-band transmission filter, a preparation method thereof and an on-chip spectral analysis and imaging system, and belongs to the field of spectral analysis and imaging.
Background
A filter is a device that individually selects light of a particular wavelength from a broad spectrum of incident light in either transmitted or reflected light. A bandpass filter is a filter that only allows light of a specific wavelength to pass through, and its main performance criteria are wavelength selectivity and operating wavelength range. Wavelength selectivity is achieved in that the band-pass wavelength range can be narrow and the transmittance of light in the band-pass wavelength range is as high as possible compared to the transmittance of light in the non-band-pass wavelength range. The operating wavelength range refers to a non-bandpass wavelength range of low transmission, the wider the better. Bandpass filtering is generally achieved by mechanisms that reflect or absorb light of other wavelengths. For example, the transmission of light with specific wavelength is obtained by using the structure of a resonant cavity, i.e. two mirrors and a medium cavity in the middle, and realizing reflection cancellation through phase matching of interference light.
Based on the principle, an on-chip spectrometer proposed by IMEC forms a series of wavelength filters through a multilayer dielectric reflector, and further obtains the spectrum analysis capability through array formation. The band-pass filter can obtain good wavelength selectivity, and the band-pass wavelength range can be less than 1% of the central wavelength. However, there are two problems, one is that the thickness of the dielectric cavity needs to be changed to change the center wavelength of the band pass, so if a series of filters with different center wavelengths of the band pass need to be prepared by different process steps to prepare a series of different thicknesses of the dielectric cavity, the process complexity is high, especially for on-chip spectrum analysis chips, the alignment problem of a large number of small-sized pixel units is brought, and in addition, the more layers of dielectric film reflectors are required as the wavelength selectivity is better, the more the preparation process steps are required; the second problem is that the operating wavelength range is limited, the low transmission wavelength range of the resonant cavity of the multilayer dielectric film reflector is determined by the high-low refractive index difference of the dielectric film, the range of the refractive index of the existing material is limited, the operating wavelength range is generally less than one fifth of the central wavelength, and the spectral analysis application in a large wavelength range is difficult to meet.
Besides the dielectric film system, the micro-nano optical resonance structure is also widely researched and shows a certain filtering function. The optical Express volume 18, page 14056, reports a band pass filter with a metal nanopore array structure, which realizes filtering by an abnormal transmission effect caused by surface plasmon resonance, can realize different band pass wavelengths by simply changing an in-plane structure, and greatly simplifies the processing technology of filter arrays with different band pass center wavelengths, but the center wavelength transmittance is only 30% lower, and the band pass wavelength range is greater than 20% of the center wavelength, so that high-precision wavelength selection is difficult to realize, and the requirement of high-resolution spectral analysis cannot be met. The Optics Express 20 th volume 21917 reports a band pass filter of a metal mirror resonant cavity, the effective refractive index of a dielectric layer is regulated and controlled by preparing hole structures with different filling rates on the dielectric layer, so that filters with different band pass center wavelengths can be prepared by one-time photoetching process, but the adjustable range of the center wavelength is limited, and the inherent defect of low transmissivity of the metal mirror resonant cavity filter exists, so that the actual requirement is difficult to meet. Optics Letters, volume 40, page 5062, reports bandpass filters of dielectric grating waveguide structures, bandpass center wavelengths can be tuned by varying the dimensions of the grating and waveguide, exhibiting high transmission and narrow bandpass wavelength range, but with a limited operating wavelength range, less than one-fifth of the bandpass center wavelength. Optics Letters volume 41, page 1913, reports a bandpass filter of a metal grating waveguide structure and its on-chip spectral application, the bandpass center wavelength can be adjusted by changing the dimensions of the grating and the waveguide, exhibiting higher transmittance and narrower bandpass wavelength range, but the free spectral width, i.e. the distance between the two transmission peak wavelengths is smaller, resulting in a limited working wavelength range, less than one seventh of the bandpass center wavelength.
It can be seen that the prior art represented by the above examples, although all exhibit band-pass filters, have limited wavelength selectivity and spectral resolution and narrow operating wavelength range, and thus are difficult to meet the technical requirements of on-chip spectral analysis and imaging applications.
Disclosure of Invention
In view of the above-mentioned deficiencies of the prior art, the present invention provides a narrow-band transmission filter and an on-chip spectral analysis and imaging system, which can simultaneously obtain a large operating wavelength range and narrow-band transmission, and realize on-chip spectral analysis and imaging capabilities with high spectral resolution and high integration.
It is a first object of the present invention to provide a narrow band transmission filter.
It is a second object of the present invention to provide an on-chip spectral analysis and imaging system.
The first purpose of the invention can be achieved by adopting the following technical scheme:
a narrow-band transmission filter comprises a substrate, wherein a grating structure is formed on the surface of the substrate, a metal/metalloid film is deposited on the grating structure, and the bandpass center wavelength is adjusted by changing the substrate material, the metal/metalloid material and the grating structure.
The first purpose of the invention can also be achieved by adopting the following technical scheme:
A narrow-band transmission filter comprises a substrate, wherein a metal/metalloid film is deposited on the surface of the substrate, a grating structure is formed on the metal/metalloid film, and the bandpass center wavelength is adjusted by changing the substrate material, the metal/metalloid material and the grating structure.
The first purpose of the invention can be achieved by adopting the following technical scheme:
a narrow-band transmission filter comprises a substrate, wherein a metal/metalloid film and a nonmetal material layer are sequentially deposited on the surface of the substrate, a grating structure is formed on the nonmetal material layer, and the center wavelength of a band-pass is adjusted by changing the substrate material, the metal/metalloid material and the grating structure.
Furthermore, the filter is prepared on the transparent substrate and is arranged into an array which is in one-to-one correspondence with the detector units of the detector array, and the grating structure faces the surface of the detector unit and is aligned and packaged.
Further, the substrate employs a dielectric layer formed on a surface layer of detector cells of the detector array.
Further, the substrate employs active layers of detector cells of a detector array, and the filter forms a schottky diode.
Furthermore, a metal reflector is arranged at the edge of the grating structure.
Furthermore, the period of the grating structure is 0.5-2 times of the central wavelength of the band-pass of the filter, and the grating height of the grating structure is smaller than 1/20 of the central wavelength of the band-pass of the filter.
Further, the thickness of the metal/metalloid film is 10-50 nm.
The second purpose of the invention can be achieved by adopting the following technical scheme:
an on-chip spectral analysis and imaging system comprises a filter array and a detector array, wherein the filter array is composed of a plurality of filter units with different band-pass center wavelengths, each filter unit adopts the narrow-band transmission filter, and the filter units of the filter array and the detector units of the detector array are correspondingly combined one by one to form the on-chip spectral analysis and imaging system; after being collimated, the collimated light irradiates the on-chip spectrum analysis and imaging system, and the signal of each detector unit in the detector array is extracted, so that spectrum and image information are obtained.
Compared with the prior art, the invention has the following beneficial effects:
1. the filter comprises a substrate, a grating structure and a metal/metalloid film, and has a large working wavelength range, so that a filter array with different band-pass center wavelengths can be constructed, filtering with different wavelengths can be realized in a large spectral range, and spectral analysis is facilitated.
2. The center wavelength of the band-pass of the filter can be adjusted by changing the period and the duty ratio of the grating structure, so that all array units can be prepared by one-step photoetching patterning, and the process complexity and the cost are reduced.
3. The filter substrate adopts the active layer of the detector unit of the detector array, namely the filter can be directly prepared on the active layer of the detector unit and used as an electrode with wavelength selectivity, the photoelectric conversion efficiency of the detector is enhanced through the electromagnetic field distribution of the space local area, and the signal-to-noise ratio of the spectral analysis is improved.
4. The filter has narrow line width in a transmission working mode, so that the filter can be directly integrated with a detector array, and can be directly integrated with the detector array, so that an on-chip spectral analysis and imaging system with high spectral resolution is realized, the system performance is greatly improved, and the system complexity is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic cross-sectional structural view of a narrow-band transmission filter according to embodiment 1 of the present invention.
FIG. 2 is a schematic diagram of an on-chip spectral analysis and imaging system according to embodiment 1, in which a filter unit of a filter array is aligned with a detector unit of a detector array.
Fig. 3 is a graph showing the calculation results of the transmission spectrum and the reflection spectrum at normal incidence of the narrow band transmission filter of example 1 of the present invention.
Fig. 4 is a graph showing the transmission spectrum calculation results of the narrow band transmission filter of embodiment 1 of the present invention at normal incidence for different bandpass center wavelength filters in the range of 700 nm to 1150 nm.
Fig. 5 is a graph showing the transmission spectrum calculation results of the narrow-band transmission filter of example 1 of the present invention at normal incidence for filters with different bandpass center wavelengths in the range of 1100 nm to 2000 nm.
Fig. 6 is a schematic cross-sectional structure view of a narrow-band transmission filter according to embodiment 2 of the present invention.
Fig. 7 is a schematic top view of a narrow band transmission filter according to embodiment 2 of the present invention.
Fig. 8 is a graph showing the calculation result of the transmission spectrum at normal incidence of the narrow band transmission filter of embodiment 2 of the present invention.
Fig. 9 is a schematic cross-sectional structure view of a narrow-band transmission filter according to embodiment 3 of the present invention.
Fig. 10 is a schematic top view of a narrow-band transmission filter according to embodiment 3 of the present invention.
Fig. 11 is a graph showing the calculation result of the transmission spectrum at normal incidence of the narrow band transmission filter of embodiment 3 of the present invention.
Fig. 12 is a schematic cross-sectional structure view of a narrow-band transmission filter according to embodiment 4 of the present invention.
Fig. 13 is a graph showing the calculation result of the transmission spectrum at normal incidence of the narrow band transmission filter of embodiment 4 of the present invention.
Fig. 14 is a schematic cross-sectional structure view of a narrow-band transmission filter according to embodiment 5 of the present invention.
Fig. 15 is a calculated transmission spectrum when the material of the active layer of the narrow band transmission filter of example 5 of the present invention is silicon.
Fig. 16 is a transmission spectrum calculated when the material of the active layer of the narrow-band transmission filter of embodiment 5 of the present invention is mercury cadmium telluride.
FIG. 17 is a schematic cross-sectional view of a narrow-band transmission filter according to embodiment 6 of the present invention
Fig. 18 is a graph showing the calculation result of the transmission spectrum at normal incidence of the narrow band transmission filter of embodiment 6 of the present invention.
Detailed Description
Technical solutions in the embodiments of the present invention will be described in detail below with reference to the drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present invention.
Example 1:
as shown in fig. 1, the present embodiment provides a narrow-band transmission filter, which includes a substrate (substrate) 1, where the substrate 1 is made of a transparent substrate, the transparent substrate is made of quartz glass, a grating structure is formed on a surface of the substrate 1, specifically, the grating structure is formed on a surface of the substrate 1 facing a detector array 3, a period of the grating structure is 1 micrometer, an etching depth of the grating structure is 30 nanometers, and an etching width of the grating structure is 500 nanometers; then, a continuous metal film is covered on the grating structure in a deposition mode, the metal film is made of at least one of gold, platinum, silver, copper, aluminum, titanium nitride and the like, the metal material of the embodiment is gold, namely the metal film is a gold film, and the grating structure and the metal film jointly form a grating 2.
It will be understood by those skilled in the art that the metal film of the present embodiment may also be replaced by a metalloid film, and the metalloid material used in the metalloid film may be at least one of boron, silicon, germanium, selenium, tellurium, polonium, arsenic, antimony, and the like.
As shown in fig. 2, the present embodiment further provides an on-chip spectrum analyzing and imaging system, which includes a filter array and a detector array 3, where the filter array is composed of a plurality of filter units with different bandpass center wavelengths, each filter unit adopts the above-mentioned narrow-band transmission filter, and the filter unit of the filter array 3 and the detector unit of the detector array are packaged in face-to-face alignment to form the on-chip spectrum analyzing and imaging system; after being collimated, the collimated light irradiates the on-chip spectrum analysis and imaging system, and the signal of each detector unit in the detector array is extracted, so that spectrum and image information are obtained.
The incident light with different wavelengths is coupled with the surface plasma wave of the grating structure at a specific incident angle, and the coupling condition is determined by the following formula:
ksinθ+mG＝±ksp (1)
where k is the wavevector in the environment of the incident optical medium, θ is the incident angle, G-2 π/P is the lattice vector of grating 2, P is the period of the grating structure, m is the diffraction order, k isspIs the wavevector of the surface plasmon wave. As can be seen from equation (1), the coupling condition is related to the incident angle, and for the convenience of data analysis, normal incidence is usually adopted, and the light to be measured needs to be collimated and then enters the filter. When the wavelength of the incident light is in the non-resonance wavelength range, the incident light cannot be coupled with the surface plasma wave of the grating 2, so most of the incident light is reflected, the metal film absorbs a small part of the incident light, and the transmitted light is very small; when the wavelength of the incident light meets the surface plasma wave coupling condition, the incident light is coupled with the surface plasma wave of the metal film, the reflected light is very small, the coupling of the incident light and the surface plasma wave of the metal enables a part of the incident light to be absorbed by the grating structure, the other part of the incident light forms transmission, namely, an obvious transmission peak is formed in the spectrum. By reasonably designing the geometric parameters of the grating structure, the radiation loss is reduced, and the narrow-band transmission can be further realized. As shown in FIG. 3, the coupling occurs at λ 0Peak transmission reaches 63% at 1022 nm, while transmission outside the 1010 to 1036 nm range is less than 6%. The full width at half maximum (FWHM) of the transmission peak was 8 nm, and the quality factor (Q)0/) exceeds 125.
By changing the period of the grating structure, a filter array with different band-pass center wavelengths in an ultra-wide working wavelength range can be realized. Fig. 4 shows the transmission spectrum calculation results of the filter array with different bandpass center wavelengths in the range of 700 nm to 1150 nm, wherein the etching depths of the grating structures are all 20 nm, the etching widths of the grating structures are all half of the period, and the thickness of the gold film is 35 nm. The filters with different bandpass center wavelengths are realized by changing the grating period, the period of the grating structure of the filter unit is changed from 700 nanometers to 1100 nanometers, and the period interval of the grating structure of the filter unit is 25 nanometers. FIG. 5 shows the transmission spectrum calculation results of filter arrays with different central wavelengths in the range of 1100 nm to 2000 nm, in which the grating etching depths are all 45 nm, the grating etching widths are all half of the periods, the thickness of the gold film is 25 nm, the periods of the grating structures are from 1100 nm to 1950 nm, and the period intervals are 50 nm. The filter arrays of different wave bands can realize the optimal filter array by adjusting the etching depth and the metal thickness.
Example 2:
as shown in fig. 6 and 7, the present embodiment provides a narrow-band transmission filter, where the filter includes a substrate 1, the substrate 1 is made of a transparent substrate, the transparent substrate is made of quartz glass, a surface of the substrate 1 is covered with a metal film 4-1 by deposition, and then a grating structure 4-2 is formed on the metal film 4-1, the metal film 4-1 of the present embodiment is a gold film, the grating structure 4-2 is a silica grating structure, where a thickness of the gold film is 35 nm, a depth of the silica grating structure is 160 nm, a width of the silica grating structure is 500 nm, and a period of the silica grating structure is 1 μm.
The design that diffracted light is provided by the dielectric grating to excite the surface plasmon resonance of the metal film 4-1 can better ensure the continuity of the metal film 4-1, further can realize the transmission of higher central wavelength by reducing the thickness of the metal film 4-1 and the absorption of the structure, and can realize a narrow-band transmission filter array in a wide working range by designing the period and the duty ratio of the grating structure 4-2. FIG. 8 is a graph of the calculated transmission spectrum at normal incidence for the filter of this example, corresponding to a filter cell exhibiting a narrow band transmission of 48% transmission at a wavelength of 1130 nm with a transmission peak width at half maximum of 25 nm. The transmission type filter based on the surface plasmon resonance coupling mechanism can realize the ultra-wideband working range by optimizing the parameters of the structural material, for example, the narrow-band transmission filter adopting the quartz substrate in the embodiment can realize at least band-pass filters with different central wavelengths in the range of 0.7 micrometers to 5 micrometers under the normal incidence condition.
Example 3:
as shown in fig. 9 and fig. 10, the present embodiment provides a narrow-band transmission filter, where the filter includes a substrate 1, the substrate 1 is a transparent substrate, the transparent substrate is made of silicon dioxide, a surface of the substrate 1 is covered with a metal film 5-1 by deposition, and then a grating structure 5-2 is formed on the metal film 5-1, the metal film 5-1 of the present embodiment is a gold film, and the grating structure 5-2 is a two-dimensional grating, specifically a two-dimensional gold disk array, where a thickness of the gold film is 20 nanometers, a period of the two-dimensional gold disk array is 1.4 micrometers, a diameter of the two-dimensional gold disk array is 1 micrometer, and a height of the two-dimensional gold disk array is 20 nanometers.
Fig. 11 is a graph of the calculation result of the transmission spectrum at normal incidence of the filter of the present example, and the corresponding filter cell exhibits a narrow-band transmission of 39% transmittance at a wavelength of 1417 nm, and a transmission peak full width at half maximum of 8 nm.
Example 4:
as shown in fig. 12, the present embodiment provides a narrow-band transmission filter, where the filter includes a substrate 1, the substrate 1 employs a dielectric layer formed on a surface layer of a detector unit of a detector array 3, that is, the filter of the present embodiment is directly prepared on the surface layer of the detector unit of the detector array 3, the dielectric layer is silicon dioxide, the thickness of the dielectric layer is 150 nm, a grating structure with a period of 0.8 μm is etched on a side of the dielectric layer facing a light source, an etching depth of the grating structure is 30 nm, and an etching width of the grating structure is 500 nm; then, a metal film is covered on the grating structure in a deposition mode, the metal film is a gold film in the embodiment, the thickness of the metal film is 30 nanometers, a grating 2 formed by the grating structure and the metal film achieves a filter function, and the grating 2 is a one-dimensional grating. The filters with different central wavelengths are realized by designing the periods of different grating structures. The optical spectrum analyzer is prepared on detector units with different response wave bands, and can realize spectral analysis application of different wave bands. The spectrum to be measured is collimated by the collimation module and then enters the band-pass filters with different central wavelengths. Fig. 13 is a calculation result of the transmission spectrum of the filter of the present embodiment at normal incidence, in which the center wavelength and the grating period ensure a good linear relationship in a wide bandwidth range, and the spatial structure of the present embodiment is more compact than that of the spatial package of embodiment 1, without considering the alignment problem of the filter unit and the detector unit.
Example 5:
as shown in fig. 14, the present embodiment provides a narrow-band transmission filter, the filter includes a substrate 1, the substrate 1 employs an active layer 3 of a detector unit of a detector array, that is, the filter of the present embodiment is directly prepared on the active layer 3 of the detector unit and forms a schottky diode, a grating structure is etched on a side of the active layer 3 facing a light source, and then a metal film is covered on the grating structure by deposition, the metal film of the present embodiment is a gold film, and the grating 2 is formed by the grating structure and the metal film. Incident light with specific wavelength can be transmitted in a corresponding filter, absorbed by silicon material and realize photoelectric conversion of interband transition, meanwhile, the part of the incident light absorbed by gold realizes photoelectric conversion of interband transition based on a photon internal emission mechanism, and both photoelectric conversion mechanisms contribute to a photoelectric detector, so that the photoelectric conversion efficiency is enhanced. The function of the filter in different wave band ranges is realized by selecting different photoelectric semiconductor materials. FIG. 15 is a calculated transmission spectrum for an active layer of silicon, where the period of the grating structure is 1 micron, the etching depth of the grating structure is 20 nm, the etching width of the grating structure is 500 nm, the thickness of the gold film is 40 nm, and the filter array design with visible silicon as the active layer can cover the visible near infrared band; fig. 16 is a transmission spectrum calculated when the material of the active layer is mercury cadmium telluride, in which the period of the grating structure is 8 micrometers, the etching depth of the grating structure is 120 nanometers, the etching width of the grating structure is 4 micrometers, and the thickness of the gold film is 20 nanometers. The filter array design with mercury cadmium telluride as the active layer can be used for spectral analysis application of infrared bands.
Example 6:
the calculated spectrum results in the above embodiments 1-5 are based on the grating structure with infinite number of cycles, but in practical applications, the number of cycles of the grating structure is always limited, and especially in on-chip spectrum analysis and spectrum imaging applications, finer spectrum and higher resolution imaging can be obtained with less number of cycles of the grating structure. As shown in fig. 17, the number of cycles of the grating structure can be effectively reduced by arranging the metal reflector 6 at the edge of the grating structure, wherein filters with different band-pass center wavelengths are prepared on the substrate 1, the substrate 1 is made of quartz glass, a microcavity with a length of 5.2 microns and a height of 1.6 microns is etched on the substrate 1, two sides of the microcavity are respectively covered with a layer of gold film reflector 6 with a thickness of 100 nanometers, the internal length of the microcavity is 5 microns, and then five grating structures with a period of 1 micron are etched in the microcavity, the etching depth of the grating structures is 30 nanometers, and the width of the grating grooves is 500 nanometers; further, a 40-nanometer gold film covers the grating structure, the gold film and the grating structure jointly form the grating 2, and the introduced metal reflector 6 reflects the plasma waves of which the surfaces are covered by the gold film for multiple times back and forth in the plane direction, so that the effective periodicity of the grating structure is increased. As shown in fig. 18, the infinite period grating structure exhibits a narrow-band transmission of 40% transmittance at a wavelength of 1019 nm and a full width at half maximum of 11 nm, while the transmission spectrum corresponding to the five period grating structure has no filter characteristics, and exhibits a low transmittance as a whole, and when a mirror structure is added to the edge of the five period grating structure, the infinite period grating structure exhibits a narrow-band transmission of 30% transmittance at a wavelength of 1029 nm and a full width at half maximum of 14 nm. The design of the narrow-band transmission filter of the embodiment can realize filtering of different wavelengths in a large spectral range, effectively reduces the size of a single filter unit by further introducing the reflector, and realizes a function of hyperspectral imaging with hyperspectral resolution.
In conclusion, the filter has a large working wavelength bandwidth and a narrow pass band, and the filters with different central wavelengths can be obtained by once graphic processing, so that the filter can be directly integrated with a detector array to form an on-chip spectral analysis and imaging system, the system performance is greatly improved, and the system complexity is reduced.
The above description is only for the preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the scope of the present invention.
Claims (8)
1. A narrow-band transmission filter is characterized by comprising a substrate, wherein a grating structure is formed on the surface of the substrate, and a metal/metalloid film is deposited on the grating structure; or depositing a metal/metalloid film on the surface of the substrate, and forming a grating structure on the metal/metalloid film; or a metal/metalloid film and a nonmetal material layer are sequentially deposited on the surface of the substrate, and a grating structure is formed on the nonmetal material layer;
the metal/metalloid film is a continuous metal/metalloid film; adjusting the center wavelength of the band-pass by changing the substrate material, the metal/metalloid material and the grating structure; by changing the period of the grating structure, a filter array with different band-pass center wavelengths in an ultra-wide working wavelength range is realized.
2. The narrow-band transmission filter of claim 1, wherein the filter is fabricated on a transparent substrate and arranged in an array corresponding one-to-one to the detector cells of the detector array, the grating structure being packaged in alignment facing the detector cell surface.
3. The narrow-band transmission filter of claim 1, wherein the substrate employs a dielectric layer formed on a surface layer of detector cells of the detector array.
4. The narrow-band transmission filter of claim 1, wherein the substrate employs active layers of detector cells of a detector array, the filter forming a schottky diode.
5. The narrow band transmission filter of claim 1, wherein the edges of the grating structure are provided with metal mirrors.
6. The narrow-band transmission filter of claim 1, wherein the grating structure has a period of 0.5 to 2 times the center wavelength of the filter bandpass, and the grating structure has a grating height of less than 1/20 times the center wavelength of the filter bandpass.
7. The narrow-band transmission filter of claim 1, wherein the metal/metalloid film has a thickness of 10 to 50 nanometers.
8. An on-chip spectral analysis and imaging system, comprising a filter array and a detector array, wherein the filter array is composed of a plurality of filter units with different bandpass center wavelengths, each filter unit adopts a narrow-band transmission filter according to any one of claims 1 to 7, and the filter units of the filter array and the detector units of the detector array are combined in a one-to-one correspondence manner to form the on-chip spectral analysis and imaging system; after being collimated, the collimated light irradiates the on-chip spectrum analysis and imaging system, and the signal of each detector unit in the detector array is extracted, so that spectrum and image information are obtained.
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