阅读说明：本技术 一种集成型多组分红外气体探测器 (Integrated multi-component infrared gas detector ) 是由 赖建军 远志昊 江湃 曹伟杰 于 2020-08-12 设计创作，主要内容包括：本发明公开了一种集成型多组分红外气体探测器,包括自上而下设置的光学芯片与红外探测器芯片,光学芯片下表面包括至少三个聚焦光学单元,每个聚焦光学单元为一个超表面透镜；红外探测器芯片包括至少三个红外探测单元,其中一个作为参考单元,且红外探测单元与聚焦光学单元一一对应；红外探测器芯片的探测波长覆盖中波红外与长波红外。本发明目的在于通过在红外探测器芯片上方设置带有聚焦光学单元的光学芯片,以解决现有技术的红外气体探测系统在对多组分气体进行高灵敏探测时探测灵敏度不足、系统体积大与集成度低的问题。(The invention discloses an integrated multi-component infrared gas detector, which comprises an optical chip and an infrared detector chip which are arranged from top to bottom, wherein the lower surface of the optical chip comprises at least three focusing optical units, and each focusing optical unit is a super-surface lens; the infrared detector chip comprises at least three infrared detection units, wherein one infrared detection unit is used as a reference unit, and the infrared detection units correspond to the focusing optical units one to one; the detection wavelength of the infrared detector chip covers medium wave infrared and long wave infrared. The invention aims to solve the problems of insufficient detection sensitivity, large system volume and low integration level when an infrared gas detection system in the prior art carries out high-sensitivity detection on multi-component gas by arranging an optical chip with a focusing optical unit above an infrared detector chip.)

1. The integrated multi-component infrared gas detector is characterized by comprising an optical chip and an infrared detector chip which are arranged from top to bottom, wherein the lower surface of the optical chip comprises at least three focusing optical units, and each focusing optical unit is a super-surface lens;

the infrared detector chip comprises at least three infrared detection units, wherein one infrared detection unit is used as a reference unit, and the infrared detection units correspond to the focusing optical units one by one;

the detection wavelength of the infrared detector chip covers medium wave infrared and long wave infrared.

2. The integrated multicomponent infrared gas detector according to claim 1, wherein each of the super-surface lenses comprises a plurality of cylindrical units having the same height, and the height of the cylindrical units satisfies h ≧ λ_max/(n_s-n_i) Wherein λ is_maxAt the maximum infrared detection wavelength, n_sAnd n_iRespectively the medium refractive index and the ambient material refractive index of the cylindrical unit.

3. The integrated multicomponent infrared gas detector according to claim 2, wherein the optical chip comprises at least three filtering optical units on the upper surface, the filtering optical units are in one-to-one correspondence with the focusing optical units, and each filtering optical unit is in a metal hole array structure.

4. The integrated multi-component infrared gas detector according to claim 3, wherein no gap is formed between adjacent focusing optical units.

5. The integrated multicomponent infrared gas detector according to claim 3, wherein the filtering optical unit is made of silver, the metal hole array structure comprises a plurality of metal holes, the period of the metal holes ranges from 3 to 12 μm, the ratio of the diameter to the period of the metal holes ranges from 20 to 35%, and the thickness ranges from 0.6 to 1.5 μm.

6. The integrated multicomponent infrared gas detector according to claim 3, wherein a spacer chip is disposed between the optical chip and the infrared detector chip to provide a specific distance between the optical chip and the infrared detector chip.

7. The integrated multicomponent infrared gas detector according to claim 6, wherein the spacer chip is provided with a circular hole in or in the middle inside.

8. The integrated multicomponent infrared gas detector according to claim 1, wherein the detection wavelengths of the infrared detector chip comprise 3.5 μm, 9.7 μm and 10.6 μm.

9. The integrated multicomponent infrared gas detector according to claim 1, wherein the infrared detection unit comprises any one or more of a microbolometer detector, a thermopile detector, and a pyroelectric detector.

10. The integrated multi-component infrared gas detector according to claim 1, wherein the infrared detection units are arranged in a fan shape; or in a 3X3 matrix with the middle infrared detection unit as a reference unit.

Technical Field

The invention belongs to the technical field of gas sensing, and particularly relates to an integrated multi-component infrared gas detector.

Background

With the increasingly wide application of infrared spectrum gas detection technology in the fields of food detection, fruit and vegetable storage and transportation, biochemical industry and the like, people have a changing demand for infrared gas detectors, and have a strong demand for highly sensitive detection of various gases. The traditional multi-component infrared gas detector usually combines the packaged single-component detectors simply, so that the occupied volume is large, and the design of a light path is difficult to compact. Detection of multi-band or multi-component gases is currently possible using FP cavity tunable filters using only a single broad spectrum detector, such as the techniques described in the literature (Shangzhi Li, et. al., Simulanous multi-gas detection between 3 and 4 μm based on a 2.5-mmultipas cell and a structured Fabric-P rot filter detector, Spectroscopic acta Part A: Molecular and biological Spectroscopy,2019,216: 154-. The multi-component gas detection device has the advantages that the required wavelength can be continuously selected and adjusted in a certain spectral range, but the problem of limited adjustable range exists in the FP cavity filter, and multi-component gas detection with absorption wavelengths in medium-wave and long-wave infrared bands is difficult to simultaneously consider. Moreover, the FP cavity tunable filter has a high cost, and its use is greatly limited.

Disclosure of Invention

In view of the above defects or improvement requirements of the prior art, the present invention provides an integrated multi-component infrared gas detector, which aims to solve the problems of low detection sensitivity, large volume and low integration level of the infrared gas detection system in the prior art when performing high-sensitivity detection on multi-component gas by arranging an optical chip with a focusing optical unit above an infrared detector chip.

According to one aspect of the invention, an integrated multi-component infrared gas detector is provided, which comprises an optical chip and an infrared detector chip arranged from top to bottom, wherein the lower surface of the optical chip comprises at least three focusing optical units, and each focusing optical unit is a super-surface lens; the infrared detector chip comprises at least three infrared detection units, wherein one infrared detection unit is used as a reference unit, and the infrared detection units correspond to the focusing optical units one by one; the detection wavelength of the infrared detector chip covers medium wave infrared and long wave infrared.

Preferably, each super-surface lens comprises a plurality of cylindrical units with the same height, and the height of each cylindrical unit satisfies h ≧ lambda_max/(n_s-n_i) Wherein λ is_maxAt the maximum infrared detection wavelength, n_sAnd n_iRespectively the medium refractive index and the ambient material refractive index of the cylindrical unit.

Preferably, the upper surface of the optical chip comprises at least three filtering optical units, the filtering optical units correspond to the focusing optical units one by one, and each filtering optical unit is of a metal hole array structure.

Preferably, there is no gap between adjacent focusing optical units.

Preferably, the filtering optical unit is made of silver, the metal hole array structure comprises a plurality of metal holes, the period range of the metal holes is 3-12 μm, the ratio of the diameter of the metal holes to the period is 20-35%, and the thickness range is 0.6-1.5 μm.

Preferably, a pad chip is disposed between the optical chip and the infrared detector chip to provide a specific distance between the optical chip and the infrared detector chip.

Preferably, the pad chip is provided with a round hole in the middle or in the middle.

Preferably, the detection wavelengths of the infrared detector chip include 3.5 μm, 9.7 μm, and 10.6 μm.

Preferably, the infrared detection unit comprises any one or more of a microbolometer detector, a thermopile detector and a pyroelectric detector.

Preferably, the infrared detection units are distributed in a fan shape; or in a 3X3 matrix with the middle infrared detection unit as a reference unit.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) the infrared gas detector provided by the invention comprises the optical chip, the surface of the optical chip comprises the focusing optical unit, and the detection wavelength of the infrared detector chip covers the medium wave infrared and the long wave infrared, so that the effective detection of at least two gases can be realized. In addition, the detector has high integration level, and the volume and the manufacturing cost of the gas sensing system can be effectively reduced.

(2) Because no gap exists between adjacent focusing optical units of the infrared gas detector, the optical chip has larger area and higher filling factor than the infrared detector chip, the infrared radiation collecting capability is stronger, the energy density of electromagnetic waves received by the detection unit can be improved exponentially, and the detection response rate and sensitivity are further improved.

Drawings

FIG. 1 is a vertical cross-sectional view of an embodiment of a three-layer four-channel integrated multi-component infrared gas detector of the present invention;

FIG. 2 is a schematic diagram of a surface structure of a gasket chip;

fig. 3 is a schematic view of the surface structure of the infrared detector chip.

FIG. 4 is a schematic diagram of the top surface structure of an optical chip;

FIG. 5 is a schematic diagram of a filtering optical unit formed by a metal hole array structure on an optical chip;

FIG. 6 is an infrared transmission spectrum of the filtering optical unit; wherein, FIG. 6(a) is a medium wave infrared transmission spectrum, and FIG. 6(b) is a long wave infrared transmission spectrum;

FIG. 7 is a schematic diagram of the bottom surface structure of an optical chip;

FIG. 8 is a schematic cross-sectional view of a super-surface lens in the super-surface lens array and a schematic structural view of a single cylindrical unit constituting the super-surface lens;

FIG. 9 is a field strength distribution at the focus of a four-channel super surface lens array;

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides an integrated multi-component infrared gas detector as an embodiment, which comprises an optical chip and an infrared detector chip which are arranged from top to bottom, wherein the lower surface of the optical chip comprises at least three focusing optical units, each focusing optical unit is a super-surface lens and can focus filtered infrared electromagnetic radiation, and the focusing optical units are manufactured on the same substrate and jointly form a super-surface lens array; the infrared detector chip comprises at least three infrared detection units, wherein one infrared detection unit is used as a reference unit, and the infrared detection units correspond to the focusing optical units one to one; the detection wavelength of the infrared detector chip covers medium wave infrared and long wave infrared. The infrared gas detector of this structure can realize the effective detection of two kinds of gases at least. In addition, the detector has high integration level, and the volume and the manufacturing cost of the gas sensing system can be effectively reduced.

As another embodiment, each super-surface lens comprises a plurality of cylindrical units with the same height, and the height of each cylindrical unit satisfies h ≧ λ_max/(n_s-n_i) Wherein λ is_maxAt the maximum infrared detection wavelength, n_sAnd n_iRespectively the dielectric index and the ambient index of refraction of the cylindrical cell. Through the super-surface lens array, infrared radiation energy corresponding to multi-component gas with absorption wavelengths in medium-wave and long-wave infrared bands can be collected to respective detector units at the same time. Because the lens array can be manufactured by one-time photoetching and one-time etching, the manufacturing cost of the lens array is low, and the optical chip is light and thin.

As another embodiment, the upper surface of the optical chip includes at least three filtering optical units, which can filter the medium-wave and long-wave infrared electromagnetic radiation, the filtering optical units correspond to the focusing optical units one by one, and each filtering optical unit is in a metal hole array structure.

As another embodiment, no gap is formed between adjacent focusing optical units, so that the optical chip has a larger area and a higher filling factor than the infrared detector chip, the infrared radiation collecting capability is stronger, the energy density of electromagnetic waves received by the detection unit can be improved in multiples, and the detection response rate and the sensitivity are further improved.

In another embodiment, the filter optical unit is made of silver, the metal hole array structure includes a plurality of metal holes, the period of the metal holes is 3-12 μm, the ratio of the diameter of the metal holes to the period is 20-35%, the thickness h is 0.6-1.5 μm, and the transmittance is relatively high within the parameter range.

As another example, a spacer chip is disposed between the optical chip and the infrared detector chip to provide a specific distance between the optical chip and the infrared detector chip.

As another embodiment, a circular hole is arranged in the middle or in the hollow inside of the gasket chip, so that necessary thermal isolation can be provided between the detection unit on the detector chip and other chips; when the middle is a round hole, the optical chip can be provided with a focus and an optical path window.

As another example, the multi-component gas comprises ethanol, ammonia gas and ethylene, and the detection wavelengths of the corresponding infrared detector chips are 3.5 μm, 9.7 μm and 10.6 μm respectively.

As another embodiment, the infrared detection unit comprises any one or more of a microbolometer detector, a thermopile detector, and a pyroelectric detector, all of which have a broad spectral response capability covering mid-to long-wavelength infrared (3-12 μm).

As a preferred embodiment of the present invention, as shown in fig. 1, a vertical cross-sectional view of an embodiment of a four-channel integrated multi-component infrared gas detector with a three-layer structure includes an optical chip 100, a gasket chip 200, and an infrared detector chip 300, which are disposed from top to bottom. The optical chip 100 includes four filtering optical units 101 on the upper surface and four focusing optical units 102 on the lower surface, and the optical chip 100 is used for filtering incident broad-spectrum electromagnetic waves out of electromagnetic waves with four channels and corresponding wavelengths and focusing the electromagnetic waves to improve the energy density of incident radiation. The four-channel optical chip corresponds to the absorption wavelength of the three component gases (ethanol 3.5 μm, ammonia 9.7 μm and ethylene 10.6 μm) and a reference wavelength of 3.9 μm. The optical chip 100 is made of medium-long wave infrared transparent materials such as silicon, germanium, calcium fluoride and the like. The spacer chip 200 has a surface structure as shown in fig. 2, and a central circular hole 201 is formed on the spacer chip 200 to provide a window for the focal length and optical path of the optical chip 100 and to provide the necessary thermal isolation between the optical chip 100 and the infrared detector chip 300. The infrared detector chip 300 includes four infrared detection units 301, as shown in fig. 3, one of which is used as a reference unit, and the infrared detection units 301 correspond to the focusing optical units 102 one to one; the detection wavelength of the infrared detector chip 300 covers the medium-wave infrared and the long-wave infrared. The infrared detection units 301 further include readout circuits 302 and pads 303, each infrared detection unit 301 can receive incident electromagnetic waves of a corresponding channel, perform detection and photoelectric conversion, and lead out electrical signals after photoelectric conversion to a related circuit test system through the readout circuits 302 and the pads 303 for subsequent signal processing. During manufacturing, the optical chip 100, the pad chip 200 and the infrared detector chip 300 are respectively manufactured, and then the three chips are bonded by using the bonding adhesive 400 or other bonding structures to manufacture an integral device.

Further, the present invention provides a specific embodiment of the optical chip 100, a structure of the filtering optical unit 101 on the upper surface of the optical chip 100 is shown in fig. 4, the filtering optical unit 101 is a metal hole array structure, as shown in fig. 5, and the filtering optical unit 101 of this embodiment adopts a metal hole type surface plasmon filtering principle. A layer of metal silver film is deposited on the upper surface of the optical chip 100 of the silicon substrate, and a metal hole array structure which is periodically arranged is designed on the silver film. The working principle is as follows: when electromagnetic waves vertically enter the periodic metal hole array structure, surface plasma waves are generated on the upper surface of the silver film and are transmitted to the lower surface of the silver film under the coupling effect of the holes, and therefore filtering of the electromagnetic waves of specific wave bands is achieved. The metal vias in the metal via array structure in fig. 5 have three structural parameters: r is the radius of the hole, P is the period of the hole, and h is the thickness of the silver film. By adjusting the three structural parameters of the metal hole, the resonance characteristic of the surface plasma can be effectively controlled, and further, the effective filtering of electromagnetic waves with the four channel wavelengths of 3.5 microns of ethanol, 9.7 microns of ammonia gas, 10.6 microns of ethylene and 3.9 microns is realized. The wavelength of the surface plasmon wave can be calculated according to the following formula:

wherein i and j are electromagnetic wave mode orders,_m、_dthe dielectric constants of the silver film and the silicon substrate are respectively, and it can be seen that the wavelength of the surface plasmon wave generated by the metal hole structure is mainly related to the period P of the metal hole, in addition to the dielectric constants of the silver film and the substrate. The radius r of the metal hole and the silver film thickness h also affect the intensity and bandwidth of the transmission peak. Through weighing, a better parameter is determined, such as the thickness of the silver film is 1.1 μm, and the combination of the period p and the hole diameter r corresponding to 2 medium-wave and 2 long-wave infrared transmission wavelengths is (3.44 μm, 0.1 μm), (3.84 μm, 1.0 μm), (9.66 μm, 2.2 μm), (10.56 μm, 2.4 μm), respectively. Under these parameters, 4 detection wavelengths all have relatively high transmittance, and the infrared transmission spectrum is shown in fig. 6. In order to obtain higher transmittance at the same time, the structure parameter range of the metal hole array structure is as follows: the period is close to the detection wavelength (deviation is less than 0.15 μm), and the duty cycle (i.e. the ratio of the hole diameter to the period) of the metal hole is: medium wave infrared 25-35%, long wave infrared 20-30%; the thickness of the metal film is 0.6 to 1.5 μm.

Further, the focusing optical unit 102 on the lower surface of the optical chip 100 is configured as shown in fig. 7, and the focusing optical unit 102 on the lower surface of the optical chip 100 corresponds to the filtering optical unit 101 on the upper surface one by one, and plays a role in focusing the filtered infrared radiation. The focusing optical element 102 is a super-surface lens that includes a plurality of cylindrical elements of equal height. The cross section of the super-surface micro-lens and the structural schematic diagram of a single cylindrical unit are shown in fig. 8, and all the cylindrical units adopt the same high-refractive-index dielectric material and structural form, except that the radius and the structural period of the cylindrical units are different.

Each cylindrical element can be regarded as a resonant structure with a lower quality factor and can be regarded as a truncated waveguide. The height of the cylindrical cell (i.e., the height of the super-surface lens) is h, the radius is r, and the structure period is P. Research shows that the effective control of electromagnetic waves with different wavelengths can be realized by changing the radius r, and the period P can effectively adjust the resonance characteristic of the cylindrical unit. Under the appropriate structural parameters, the super-surface lens array with equal surface height can be obtained. The cylindrical units are used as microstructure units for constructing a multi-channel super-surface lens array, and the emergent electromagnetic wave phase of the cylindrical units can be expressed as

Wherein

Is the initial phase of the electromagnetic wave, h is the height of the cylindrical element, n_effRepresents its effective refractive index, k₀2 pi/λ is the wave number of the electromagnetic wave under vacuum. Effective refractive index n_effRefractive index n of medium_sAnd refractive index n of the surrounding material_iRelated, therefore, the range is limited to n_i≤n_eff≤n_s. The effective refractive index n can be realized by regulating and controlling the radius r of the cylindrical unit_effThe phase difference of the outgoing electromagnetic wave under the condition of different radii r is expressed as:

wherein the content of the first and second substances,

andrespectively, radius is r₁And r₂Effective refractive index of cylindrical cell. According to the limit condition of effective refractive index, the maximum phase difference of the emergent electromagnetic wave isIn order to realize the complete manipulation of electromagnetic waves, cylindrical unit structures with different radiuses must be capable of reaching the range of 0-2 pi for the wave front phase regulation of the electromagnetic waves. The minimum height of the cylindrical unit is determined according to the maximum wavelength of the electromagnetic wave to be manipulated, namely the height of the cylindrical unit is equal to or more than h and lambda_max/(n_s-n_i). When the cylindrical medium and the ambient medium are respectively silicon (n)_s3.42) and air (n)_i1), the height of the cylindrical unit must satisfy h ≧ 4.38 μm for a maximum wavelength λ of 10.6 μm.

The material of the cylindrical unit in this embodiment is silicon, and the height is set to be 5 μm; the focal length of the super-surface lens is 500 mu m, the shape of the lens is square, and the side length is 500 mu m. Through analysis of the phase and transmittance distribution of the cylindrical units with the medium wave band and the long wave band respectively, the change amount of the phase of the infrared band with the medium wave band can reach 2 pi when the radius r of the cylindrical units is in the area of 0.5-1 mu m, and the transmittance is higher than 0.50; when the radius of each cylindrical unit is 0.5-2.3 μm, the phase variation corresponding to the long-wave infrared band can cover 0-2 pi, and the transmittance can reach above 0.50.

The phase distribution in the xz plane required to achieve the focusing function can be calculated by the following formula:

wherein, the focus focal length is set to be f is 500 μm, and m is an integer. The phase distribution for achieving the same focal length focusing function is not the same for electromagnetic waves of different wavelengths. When the wavelength of the electromagnetic wave is 3.5 μm, 3.9 μm, 9.7 μm and 10.6 μm, the radius distribution of the cylindrical array on the xz plane can be calculated according to the phase calculation formula and the relationship between the corresponding wavelength phase and the cylindrical radius, so as to obtain the required phase distribution. Finally, a multi-channel super-surface lens array is designed, and consists of super-surface lenses corresponding to 4 electromagnetic waves with different wavelengths. The average focusing efficiency of all the super-surface lenses was greater than 85%, and the resulting 4-wavelength converging spot cross-section is shown in fig. 9. Through research, compared with a non-integrated lens, the infrared radiation energy density on the integrated infrared gas detector can be increased by dozens to hundreds of times, and the response rate and the sensitivity of the detector are greatly improved.

Although the embodiment of the invention provides a scheme of a four-unit three-component infrared gas detector, the invention can be easily popularized to detectors with more gas components, such as six-unit five-component gas detection which can be distributed along a circumference sector, and the like. Also for example, a 9-cell device arranged in a 3 × 3 matrix, wherein the middle detection cell can be used as a reference cell and the peripheral 8 cells can be used as gas detection cells. The compact arrangement can reduce the area of the detector chip and reduce the manufacturing cost of the detector chip. The energy density of the radiation focused to the detection unit can be significantly increased by increasing the area of the optical unit on the optical chip.

Compared with the prior art, the integrated multi-component infrared gas detector provided by the invention can realize effective detection of multi-channel multi-component gas; an optical chip with a filtering optical unit and a focusing optical unit is arranged in front of an infrared detector chip, so that the energy density of electromagnetic waves received by the infrared detector can be effectively improved, and the response rate and the sensitivity of a device are improved; by improving the integration level, the size and power consumption of the device can be greatly reduced, and meanwhile, the manufacturing cost is reduced. The technology of the invention can be applied to infrared gas sensors, other infrared multispectral detection devices such as micro infrared spectrometers and the like, and is used for analyzing and detecting the concentration of multiple substance components in the fields of food, chemical industry, agriculture, biomedicine, environmental monitoring and the like.

The above-described embodiments are merely preferred embodiments of the present invention, and it will be apparent to those skilled in the art that various types of detectors may be designed without inventive faculty based on the teachings of the present invention, and all changes, modifications, substitutions and alterations to the equivalent scope of the claims of the present invention should be covered by the present invention without departing from the principle and spirit of the invention.