A composite grating mid-infrared thermal emitter for gas spectroscopy

Abstract

The application discloses a composite grating middle infrared thermal emitter for gas spectrum detection, which comprises a composite grating layer, an intermediate layer and a substrate layer arranged in sequence from top to bottom; the composite grating layer is used for placing a metal grating structure; the intermediate layer is a phase change material, has different optical parameters under different phase state structures and is used for regulating and controlling the wave band range of an emission spectrum; and the substrate layer is made of metal material; when electromagnetic waves are incident from the composite grating layer and pass through the intermediate layer and the substrate layer, guided mode resonance and Fabry-Perot resonance can be excited, multiple narrow spectrum band emission peaks can be excited in the middle infrared wave band, the absorption spectral lines of different required to-be-detected gases are matched, and synchronous and accurate detection of multi-component gases is realized.

Description

Technical Field

[0001] The present invention relates to a mid-infrared heat emitter, in particular to a composite grating mid-infrared heat emitter for gas spectrum detection, belonging to the technical field of thermal radiation regulation and gas detection. Background Art

[0002] Non-dispersive infrared gas detection technology mainly relies on optical filters to obtain mid-infrared detection light in a specific band. The quality of the detection light is limited by the filtering performance of the optical filter. However, the full width at half-wavelength of the existing optical filters used for gas detection is relatively wide. Metasurface emitters can obtain emission light in an ultra-narrow spectral band and can be used to achieve high-precision detection of single-component or multi-component gases. However, once the geometric parameters of the metasurface thermal emitter are determined, the adjustability of the emitted light decreases. In addition, the emission spectrum of the metasurface thermal emitter is mainly adjusted by changing the polarization state of the incident wave, which significantly increases the difficulty of preparing and applying multi-component gas sensors.

[0003] From the above, it can be seen that the existing methods cannot achieve synchronous and accurate detection of multi-component gases through integrated, high-precision, and spectrally tunable mid-infrared thermal emitters, which is the research direction required by the present invention. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention provides a composite grating mid-infrared thermal emitter for gas spectral detection, which utilizes the optical properties of phase change materials in different phase structures to respectively excite and form multiple groups of mid-infrared band emission peaks, and through a combination of guided mode resonance and Fabry-Perot resonance, excites multiple narrow-band emission peaks in the same band, thereby matching the absorption spectra of different required gases to be tested, and realizing synchronous and accurate detection of multi-component gases.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a composite grating mid-infrared thermal emitter for gas spectrum detection, comprising a composite grating layer, an intermediate layer and a base layer arranged in sequence from top to bottom;

[0006] The composite grating layer is used to place a metal grating structure, which is composed of multiple grating units arranged flatly in the same plane; each grating unit is composed of two metal gratings of different widths and the same length arranged parallel to each other, and the spacing between the two metal gratings in the grating unit is smaller than the spacing between two adjacent grating units;

[0007] The intermediate layer is a phase change material, which has different optical parameters in different phase structures and is used to adjust the wavelength range of the emission spectrum;

[0008] When electromagnetic waves are incident from the composite grating layer and pass through the intermediate layer and the base layer, guided mode resonance and Fabry-Perot resonance can be excited, multiple narrow spectral band emission peaks are excited in the mid-infrared wave band, the absorption spectral lines of different required to-be-detected gases are matched, and the synchronous detection of multi-component gases is realized.

[0009] Further, the composite grating layer is made of silver material.

[0010] Further, the widths of the two metal gratings of the grating unit are 600nm-900nm and 400nm-700nm respectively.

[0011] Further, the thickness of the composite grating layer is 10nm-150nm.

[0012] Further, the spacing of the two metal gratings in the grating unit is 100nm-400nm; and the spacing of adjacent grating units is 200nm-500nm.

[0013] Further, the intermediate layer is made of phase change material Ge2Sb2Se5, the phase change material Ge2Sb2Se5 is in amorphous state structure at normal temperature, the refractive index is 3.05; is converted into crystalline state structure when the temperature is greater than 250 DEG C, the refractive index is 3.39; and the extinction coefficient of the two kinds of phase state structures is close to 0. The phase change material Ge2Sb2Se5 can also realize phase state regulation by external electric field, and the voltage of the external electric field is generally greater than 3V.

[0014] Further, the thickness of the intermediate layer is 800nm-1200nm.

[0015] Further, the base layer is made of metal material.

[0016] Further, the wave band range is the mid-infrared wave band with wavelength of 3.0-10.0um.

[0017] Further, the composite grating layer is a rectangular body, and electromagnetic waves are incident in a direction perpendicular to the composite grating structure.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] 1. The present application adopts a composite grating layer, an intermediate layer and a base layer to form a mid-infrared thermal emitter, when electromagnetic waves are incident into the mid-infrared thermal emitter, the composite metal grating structure with a specific layout, the phase change material as the intermediate layer and the metal base cooperate with each other to excite guided mode resonance and Fabry-Perot resonance, thereby exciting multiple narrow spectral band emission peaks in the mid-infrared wave band.

[0020] 2, The application utilizes the phase change characteristics of the phase change material Ge2Sb2Se5 to adjust the optical parameters of the intermediate layer, excites multiple groups of different mid-infrared waveband emission peaks in the crystalline structure and amorphous structure respectively, and each waveband has multiple emission peaks, which match the absorption spectral lines of different required gases to be detected; a reference peak is set to calibrate the attenuation degree of the emission peak, and the detection error of external environmental factors (such as water vapor, temperature, air pressure, etc.) is reduced.

[0021] 3, The application optimizes the resonant response performance of the composite grating structure by specifically limiting the thickness, width, pitch of the two metal gratings, the thickness of the phase change material, and the pitch and the period length in the x direction of the grating unit, so that the mid-infrared thermal emitter in the application is suitable for synchronous and accurate detection of multi-component gases, and through parameter optimization design, the detection accuracy and efficiency of the gas sensor reach the optimal effect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a gas sensor structure framework diagram composed of the mid-infrared thermal emitter in the application;

[0023] Figure 2 is a schematic diagram of the overall structure of the application;

[0024] Figure 3 is the spectral emissivity of the application in the 3.3~5.0μm waveband range, corresponding to the absorption spectral lines of methane, carbon monoxide and the set reference peak respectively;

[0025] Figure 4 is the spectral emissivity of the application in the 3.0~4.5μm waveband range, corresponding to the absorption spectral lines of acetylene, hydrogen chloride and carbon dioxide.

[0026] In the figure: H is the thickness of the phase change material, h is the height of the metal grating, L1 and L2 are the widths of the two metal gratings in the grating unit respectively, T1 is the pitch of the two metal gratings in the grating unit, T2 is the pitch of the two adjacent grating units, D is the thickness of the substrate, P x is the length of a grating unit in the x direction. DETAILED DESCRIPTION

[0027] The application will be further described below.

[0028] As Figure 2 shown, a composite grating mid-infrared thermal emitter for gas spectral detection comprises a composite grating layer, an intermediate layer and a substrate layer arranged in order from top to bottom;

[0029] The composite grating layer is a rectangular body made of silver material, a coordinate system is established with two perpendicular edges of the composite grating structure being respectively set as x and y directions, and the height direction of the composite grating structure being set as z direction; the composite grating structure is composed of a plurality of grating units arranged in the same plane; each grating unit is composed of two metal gratings with different widths and the same length arranged in parallel with each other, the widths of the two metal gratings of the grating unit are 600nm-900nm and 400nm-700nm respectively; the spacing between the two metal gratings in the grating unit is 100nm-400nm; the spacing between two adjacent grating units is 200nm-500nm; when electromagnetic waves pass through the composite grating structure, guided mode resonance and Fabry-Perot resonance can be excited, thereby forming a plurality of narrow-band emission peaks; the thickness of the composite grating layer is 10nm-150nm.

[0030] The intermediate layer is made of phase change material Ge2Sb2Se5, and the thickness is 800nm-1200nm; the phase change material is Ge2Sb2Se5, which has different optical parameters in different phase state structures and is used for adjusting the wavelength range of the emission spectrum; when the phase change material Ge2Sb2Se5 is in amorphous state at room temperature, the refractive index is 3.05; when the temperature is greater than 250℃, it is converted into crystalline state, and the refractive index is 3.39; the extinction coefficient of the phase change material Ge2Sb2Se5 in the two phase state structures is close to 0; the phase state of the phase change material Ge2Sb2Se5 can also be adjusted by an external electric field, and the voltage of the external electric field is generally greater than 3V. When in amorphous state, the incident electromagnetic wave excites multiple narrow-band emission peaks in the 3.0-4.5μm wavelength band, and when in crystalline state, the incident electromagnetic wave excites multiple narrow-band emission peaks in the 3.3-5.0μm wavelength band; the substrate layer is made of silver material.

[0031] Through the common optimization of the above various specific parameters, when the electromagnetic wave is incident in the direction perpendicular to the composite grating structure and sequentially passes through the composite grating layer, the intermediate layer and the substrate layer, the composite grating structure can excite guided mode resonance and Fabry-Perot resonance, thereby exciting multiple narrow-band emission peaks in the mid-infrared wave band; finally, the mid-infrared thermal emitter excites multiple narrow-band emission peaks in multiple mid-infrared wave bands when matching different phase state structures of Ge2Sb2Se5 (phase state adjustment is realized by heating or external electric field), and each wave band has multiple narrow-band emission peaks, which matches the absorption spectrum lines of different required gases to be detected, and realizes the synchronous and accurate detection of single-component or multi-component gases.

[0032] Test proves that:

[0033] A composite grating mid-infrared thermal emitter for gas spectrum detection was fabricated using the method of the present invention, and the specific parameters were defined as follows: the thickness of the composite grating layer was 15 nm, the widths of the two metal gratings in the grating unit were 788 nm and 588 nm, respectively, the spacing between the two metal gratings in the grating unit was 200 nm, the spacing between two adjacent grating units was 390 nm, the thickness of the phase change material was 925 nm, and the period length P of the grating unit in the x-direction was 100 nm. x It is 788nm+588nm+390nm+200nm=1966nm.

[0034] like Figure 1 As shown in FIG, the manufactured mid-infrared thermal emitter and photoelectric detector are combined into a gas detection sensor and placed on both sides of the gas pool for testing; through the test, the corresponding spectral data of the intermediate layer under different phase structures are obtained; Figure 3 As shown in the figure, when the middle layer is a crystalline structure Ge2Sb2Se5, three narrow-band emission peaks are formed in the mid-infrared band with a wavelength of 3.3~5.0μm. The central wavelengths corresponding to the three emission peaks are 3.421, 3.999 and 4.699μm, and the corresponding emissivities are 92%, 96.74% and 90.28%, respectively, matching the absorption lines of methane and carbon monoxide, and the second emission peak is set as the reference peak; Figure 4 As shown in the figure, when the middle layer is an amorphous structure Ge2Sb2Se5, three narrow-band emission peaks are formed in the mid-infrared band with a wavelength of 3.0~4.5μm. The central wavelengths of the three emission peaks are 3.078, 3.617 and 4.234μm, and the corresponding emissivities are 97.15%, 99.35% and 94.36%, respectively, matching the absorption lines of acetylene, hydrogen chloride and carbon dioxide. The infrared thermal emitter has a wavelength of 3. The quality factors Q at wavelengths of 421, 3.999, and 4.699 μm are 323.88, 242.6, and 120, respectively, and the half-wave full widths are 14.6 nm, 16.5 nm, and 39.4 nm, respectively. The quality factors Q at wavelengths of 3.078, 3.617, and 4.234 μm are 328.9, 253.15, and 141.4, respectively, and the half-wave full widths are 12.9 nm, 14.4 nm, and 29.9 nm, respectively. This shows that the mid-infrared thermal emitter of the present invention realizes high-Q three-channel spectral emission, synchronously matches the absorption spectra of different gases required to be measured, and pre-sets the reference peak to reduce the detection error caused by environmental factors, thereby realizing synchronous and accurate detection of single or multi-component gases.

[0035] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite grating mid-infrared thermal emitter for gas spectrum detection, characterized in that: It includes a composite grating layer, an intermediate layer and a base layer arranged in sequence from top to bottom; The composite grating layer is a rectangular body made of silver material, used to place the metal grating structure. The metal grating structure is composed of multiple grating units arranged flatly in the same plane. Each grating unit is composed of two metal gratings of different widths and the same length arranged parallel to each other, and the spacing between the two metal gratings in the grating unit is smaller than the spacing between two adjacent grating units. The intermediate layer is made of a phase-change material, Ge2Sb2Se5, and has a thickness of 800 nm to 1200 nm. The phase-change material, Ge2Sb2Se5, is amorphous at room temperature with a refractive index of 3.

05. When the temperature is greater than 250°C, it transforms into a crystalline structure with a refractive index of 3.

39. The phase-change material has different optical parameters in different phase structures, which are used to control the wavelength range of the emission spectrum. The base layer is made of metal material; When the electromagnetic wave is incident in a direction perpendicular to the composite grating layer and passes through the intermediate layer and the base layer, it can excite the guided mode resonance and Fabry-Perot resonance, and stimulate multiple narrow-band emission peaks in the mid-infrared band, matching the absorption spectra of different gases to be tested, and realizing the synchronous detection of multi-component gases.

2. The composite grating mid-infrared thermal emitter for gas spectrum detection according to claim 1, characterized in that: The widths of the two metal gratings of the grating unit are 600 nm to 900 nm and 400 nm to 700 nm respectively.

3. The composite grating mid-infrared thermal emitter for gas spectrum detection according to claim 1, characterized in that: The thickness of the composite grating layer is 10 nm to 150 nm.

4. The composite grating mid-infrared thermal emitter for gas spectrum detection according to claim 1, characterized in that: The spacing between two metal gratings in the grating unit is 100 nm to 400 nm; the spacing between adjacent grating units is 200 nm to 500 nm.

5. The composite grating mid-infrared thermal emitter for gas spectrum detection according to claim 1, characterized in that: The wavelength range is the mid-infrared band with a wavelength of 3.0~10.0 μm.

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