Mid-infrared waveguide gas sensor based on singular point and detection method

Abstract

The invention discloses an intermediate infrared waveguide gas sensor based on singular points, and belongs to the technical field of infrared analyte detection, the intermediate infrared waveguide gas sensor comprises a rectangular waveguide, a first runway type micro-ring resonator and a second runway type micro-ring resonator which are arranged adjacently in sequence; a first metal electrode is arranged on the annular waveguide on one side of the first runway type micro-ring resonator, and a micro air chamber is arranged on the upper surface of the annular waveguide on the other side of the first runway type micro-ring resonator; a second metal electrode is arranged on an annular waveguide on one side of the second runway type micro-ring resonator; the first runway type micro-ring resonator and the second runway type micro-ring resonator are the same in structure, and the first metal electrode and the second metal electrode are the same in structure. The two ends of the rectangular waveguide are respectively provided with a waveguide input coupling port and a waveguide output coupling port. The sensor provided by the invention has high integration level, and the gain adjustable range is increased, so that the sensor can easily reach a singular point, and the sensitivity of the sensor can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared analyte detection, and in particular relates to a mid-infrared waveguide gas sensor based on singular points and a detection method. Background Art

[0002] The core unit of the on-chip infrared gas sensor is the optical waveguide, which uses the evanescent field to detect analytes and has the advantages of small size and light weight. However, the limitation factor of the optical waveguide is small, resulting in weak gas absorption and low sensor sensitivity. The gas absorption coefficient in the mid-infrared band is larger than that in the near-infrared band, so using an optical waveguide sensor for gas detection in the mid-infrared band can improve sensitivity.

[0003] Singularity is widely used in optics, acoustics, circuits and other fields. By adjusting the gain or loss, the non-Hermitian sensor system can reach the singularity point, making the real and imaginary parts of the Hamiltonian eigenvalue degenerate, and the external disturbance ε (to be measured) can make the sensor system produce ε 1 / N Linearly dependent responses ( N is the system order), and the Hermitian sensing system has the same ε The response of non-Hermitian sensing system is linearly related to the ε <<1) has higher sensitivity, and combining the singular point with the on-chip infrared gas sensor can achieve a lower detection limit. However, at present, the singular point sensor generally adopts the solution of coupling the optical fiber cone with the microcavity, and the integration of the sensor is generally low; and the sensor generally uses rare earth ions to control the gain, which makes the adjustable gain range limited, and the use of optical pumping requires an additional light source, which increases the complexity of the system. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a mid-infrared waveguide gas sensor and a detection method based on a singular point. The present invention helps to improve the practicability of the singular point sensor by improving the integration and gain adjustment range of the singular point sensor.

[0005] The first object of the present invention is to provide a mid-infrared waveguide gas sensor based on a singular point, comprising a rectangular waveguide, a first racetrack-type microring resonator and a second racetrack-type microring resonator arranged adjacent to each other in sequence; A first metal electrode is disposed on one side of the annular waveguide of the first racetrack type microring resonator, and a micro air chamber is disposed on the upper surface of the other side of the annular waveguide of the first racetrack type microring resonator; a second metal electrode is disposed on one side of the annular waveguide of the second racetrack type microring resonator; The first racetrack-type microring resonator and the second racetrack-type microring resonator have the same structure, and the first metal electrode and the second metal electrode have the same structure; a waveguide input tapered coupling port and a waveguide output tapered coupling port are respectively provided at both ends of the rectangular waveguide.

[0006] Preferably, the first racetrack-type microring resonator comprises an upper cladding layer, a core layer, a lower cladding layer, a substrate and a bottom metal electrode arranged in sequence from top to bottom; The first metal electrode and the micro gas chamber are both connected to the top of the upper cladding layer.

[0007] Preferably, the first metal electrode comprises a top metal electrode, a first insulating layer and a second insulating layer are symmetrically arranged on both sides of the top of the substrate, an upper cladding layer, a core layer and a lower cladding layer are located between the first insulating layer and the second insulating layer, and the upper cladding layer, the core layer and the lower cladding layer are connected to the first insulating layer and the second insulating layer respectively; The top metal electrode is arranged on the outer sides of the first insulating layer and the second insulating layer, and the top metal electrode is connected to the upper cladding layer.

[0008] Preferably, the core layers of the first racetrack-type microring resonator, the second racetrack-type microring resonator, the rectangular waveguide, the waveguide input tapered coupling port and the waveguide output tapered coupling port are all quantum well structures.

[0009] Preferably, the materials of the upper cladding layer, the lower cladding layer and the substrate are InP, the materials of the first insulating layer and the second insulating layer are SiO2, and the materials of the bottom metal electrode and the top metal electrode are Au.

[0010] Preferably, the micro air chamber is provided with an air chamber air inlet and an air chamber air outlet.

[0011] Preferably, the material of the micro air chamber is polydimethylsiloxane.

[0012] A second object of the present invention is to provide a detection method for a mid-infrared waveguide gas sensor based on a singular point, comprising the following steps: S1, coupling the light emitted by the mid-infrared laser to the waveguide input tapered coupling port, and coupling the light output from the waveguide output tapered coupling port to the detector, collecting the output signal of the detector, recording the collected output signal and processing the output signal; S2: Adjust the current of the mid-infrared laser, scan the quantum well gain band of the first racetrack-type microring resonator, monitor the output signal of the sensor in real time, and obtain the output spectrum of the sensor without gain; S3: adjusting the current of the first metal electrode to change the gain of the first racetrack-type microring resonator, adjusting the current of the second metal electrode to change the resonant frequency of the second racetrack-type microring resonator, obtaining the sensor output spectrum, monitoring the degenerate state of the output signal resonant mode, and making the sensor reach a singular point; S4: introducing different concentrations of the test gas into the air inlet of the micro air chamber through the gas distribution system, the test gas changes the loss of the first racetrack-type microring resonator, collecting and processing the exhaust gas discharged from the air outlet of the air chamber, and recording the resonance mode splitting amount corresponding to the different concentrations of the test gas; S5: Analyze the mid-infrared absorption characteristics of the gas to be tested by obtaining the resonance mode splitting amounts corresponding to the gas to be tested with different concentrations.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The mid-infrared waveguide gas sensor based on singular points provided by the present invention integrates a coupling unit and a gain control unit on the same substrate, so that the prepared sensor has a high degree of integration; (2) The sensor provided by the present invention controls the gain through quantum wells, thereby increasing the adjustable gain range and making it easier for the sensor to reach the singular point; (3) The sensor provided by the present invention utilizes singular points to enhance the response to gas analytes, which can effectively improve the sensitivity of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A top view of the structure of a mid-infrared waveguide gas sensor based on a singular point provided in Example 1 of the present invention; Figure 2 is a cross-sectional view of the connection between the first metal electrode and the first racetrack-type microring resonator in Example 1 of the present invention; Figure 3 is a cross-sectional view of the first racetrack-type microring resonator in Example 1 of the present invention; Figure 4 The present invention is a flow chart for measuring the gas to be measured.

[0015] The reference numerals are as follows: 101. a first racetrack-type microring resonator; 102. a first metal electrode; 103. a second racetrack-type microring resonator; 104. a second metal electrode; 105. a rectangular waveguide; 106. a waveguide input tapered coupling port; 107. a waveguide output tapered coupling port; 108. a micro air chamber; 109. an air chamber air inlet; 110. an air chamber air outlet; 201, core layer; 202, upper cladding layer; 203, lower cladding layer; 204, substrate; 205, first insulating layer; 206, second insulating layer; 207, bottom metal electrode; 208, top metal electrode. DETAILED DESCRIPTION

[0016] The following is a description of the embodiments of the present invention. Figures 1 to 4 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0017] As shown in 1, an embodiment of the present invention provides a mid-infrared waveguide gas sensor based on singular points, specifically comprising a rectangular waveguide 105, a first racetrack-type microring resonator 101, and a second racetrack-type microring resonator 103 arranged adjacent to each other in sequence; A first metal electrode 102 is disposed on one side of the annular waveguide of the first racetrack type microring resonator 101, and a micro air chamber 108 is disposed on the upper surface of the other side of the annular waveguide of the first racetrack type microring resonator 101; a second metal electrode 104 is disposed on one side of the annular waveguide of the second racetrack type microring resonator 103; The first racetrack microring resonator 101 and the second racetrack microring resonator 103 have the same structure, and the first metal electrode 102 and the second metal electrode 104 have the same structure; and a waveguide input coupling port 106 and a waveguide output coupling port 107 are respectively provided at both ends of the rectangular waveguide 105.

[0018] In the embodiment of the present invention, the light emitted by the mid-infrared laser is coupled to the waveguide input tapered coupling port 106 and the rectangular waveguide 105 through a convex lens, and the light output from the waveguide output tapered coupling port 107 is coupled to the detector through a convex lens. The detector further couples the light to the first racetrack-type microring resonator 101, and there is optical coupling between the first racetrack-type microring resonator 101 and the second racetrack-type microring resonator 103. The mid-infrared waveguide gas sensor based on singular points provided in the embodiment of the present invention can be constructed by optical coupling between the rectangular waveguide 105, the first racetrack-type microring resonator 101 and the second racetrack-type microring resonator 103.

[0019] like Figure 3 As shown, the first racetrack-type microring resonator 101 in the embodiment of the present invention comprises an upper cladding layer 202, a core layer 201, a lower cladding layer 203, a substrate 204 and a bottom metal electrode 207 arranged in sequence from top to bottom; The first metal electrode and the micro gas chamber (108) are both connected to the top of the upper cladding layer (202).

[0020] like Figure 2As shown, the first metal electrode 102 in the embodiment of the present invention includes a top metal electrode 208, and the first insulating layer 205 and the second insulating layer 206 are symmetrically arranged on both sides of the top of the substrate 204, the upper cladding 202, the core layer 201 and the lower cladding 203 are located between the first insulating layer 205 and the second insulating layer 206, and the upper cladding 202, the core layer 201 and the lower cladding 203 are respectively connected to the first insulating layer 205 and the second insulating layer 206, the top metal electrode 208 is arranged on the outer side of the first insulating layer 205 and the second insulating layer 206, and the top metal electrode 208 is connected to the upper cladding 202.

[0021] In the embodiment of the present invention, the rectangular waveguide 105, the waveguide input tapered coupling port 106 and the waveguide output tapered coupling port 107 also have the same structure as the first racetrack type microring resonator 101 and the second racetrack type microring resonator 103, specifically, also including an upper cladding layer 202, a core layer 201, a lower cladding layer 203, a substrate 204 and a bottom metal electrode 207 arranged in sequence from top to bottom; The core layer 201 materials of the first racetrack type microring resonator 101, the second racetrack type microring resonator 103, the rectangular waveguide 105, the waveguide input tapered coupling port 106 and the waveguide output tapered coupling port 107 are all AlInAs-InGaAs, and the core layer 201 is a quantum well structure. The AlInAs-InGaAs material in this embodiment is prepared by the existing molecular beam epitaxy method; In the embodiment of the present invention, the quantum well structure of the core layer 201 in the first racetrack-type microring resonator 101 can generate gain in the mid-infrared band, and the quantum well structure of the core layer 201 in the second metal electrode 104 can adjust the resonant frequency of the second racetrack-type microring resonator 103; In the embodiment of the present invention, the materials of the upper cladding layer 202, the lower cladding layer 203 and the substrate 204 are InP, the materials of the first insulating layer 205 and the second insulating layer 206 are SiO2, and the materials of the bottom metal electrode 207 and the top metal electrode 208 are Au.

[0022] In the embodiment of the present invention, the micro air chamber 108 is provided with an air chamber air inlet 109 and an air chamber air outlet 110 , and the material of the micro air chamber 108 is polydimethylsiloxane. Example 2

[0023] The embodiment of the present invention provides a method for preparing a mid-infrared waveguide gas sensor based on a singular point according to embodiment 1, which specifically comprises the following steps: Step 1, depositing SiO2 on the surface of substrate 204 (wafer), and forming a mask pattern on the surface of substrate 204 by spin coating photoresist, exposure, and development; Step 2: forming a rectangular waveguide 105, a first racetrack-type microring resonator 101, and a second racetrack-type microring resonator 103 which are arranged adjacent to each other in sequence by dry etching; Step 3: depositing a SiO2 insulating layer on the surface of the substrate 204; Step 4: forming a mask pattern on the surface of the substrate 204 by spin coating photoresist, exposing, and developing, and forming a SiO2 window by dry etching; Step 5: Then, Au is deposited on the surface of the substrate 204; Step 6: forming a mask pattern on the surface of the substrate 204 by spin coating photoresist, exposing, and developing, and forming the first metal electrode 102 and the second metal electrode 104 by wet etching; Step 7: Grind and thin the substrate 204 , and deposit Au on the back side of the substrate 204 .

[0024] Step 8: Use an oxygen plasma treatment machine to process the device, and bond a micro gas chamber 108 made of polydimethylsiloxane material to the upper surface of the ring waveguide on the other side of the first racetrack type microring resonator 101 to prepare a mid-infrared waveguide gas sensor. Example 3

[0025] The embodiment of the present invention provides a detection method of the mid-infrared waveguide gas sensor based on singular points provided in Embodiment 1, which specifically includes the following steps: S1, coupling the light emitted by the mid-infrared laser to the waveguide input tapered coupling port 106 through a convex lens, coupling the light output from the waveguide output tapered coupling port 107 to the detector through a convex lens, using a data acquisition card to collect the output signal of the detector, and using the data acquisition card and the host computer to record and process the output signal; the mid-infrared laser in this embodiment is a mid-infrared quantum cascade laser, and the detector is a mid-infrared mercury cadmium telluride detector; S2: adjusting the current of the mid-infrared laser, scanning the quantum well gain band of the first racetrack-type microring resonator 101, monitoring the output signal of the sensor in real time through the data acquisition card and the host computer, and obtaining the output spectrum of the sensor when no gain is added; S3: adjusting the current of the first metal electrode 102 to change the gain of the first racetrack-type microring resonator 101, adjusting the current of the second metal electrode 104 to change the resonance frequency of the second racetrack-type microring resonator 103, obtaining the sensor output spectrum through the data acquisition card and the host computer, monitoring the degenerate state of the output signal resonance mode, and making the sensor reach the singular point; S4: different concentrations of the test gas are introduced into the gas chamber inlet 109 of the micro gas chamber 108 through the gas distribution system, the test gas changes the loss of the first racetrack type microring resonator 101, and the exhaust gas discharged from the gas chamber outlet 110 is collected and processed, and the resonance mode splitting amount corresponding to the different concentrations of the test gas is recorded through the data acquisition card and the host computer; S5: Analyze the mid-infrared absorption characteristics of the gas to be tested by obtaining the resonance mode splitting amounts corresponding to the gas to be tested with different concentrations.

[0026] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A mid-infrared waveguide gas sensor based on singular points, characterized in that: It comprises a rectangular waveguide (105), a first racetrack-type microring resonator (101) and a second racetrack-type microring resonator (103) which are arranged adjacent to each other in sequence; A first metal electrode (102) is provided on one side of the annular waveguide of the first racetrack type microring resonator (101), and a micro air chamber (108) is provided on the upper surface of the other side of the annular waveguide of the first racetrack type microring resonator (101); a second metal electrode (104) is provided on one side of the annular waveguide of the second racetrack type microring resonator (103); The first racetrack-type microring resonator (101) and the second racetrack-type microring resonator (103) have the same structure, and the first metal electrode (102) and the second metal electrode (104) have the same structure; and a waveguide input tapered coupling port (106) and a waveguide output tapered coupling port (107) are respectively provided at two ends of the rectangular waveguide (105).

2. The mid-infrared waveguide gas sensor based on singular points according to claim 1, characterized in that: The first racetrack-type microring resonator (101) comprises an upper cladding layer (202), a core layer (201), a lower cladding layer (203), a substrate (204), and a bottom metal electrode (207) which are arranged in sequence from top to bottom; The first metal electrode and the micro gas chamber (108) are both connected to the top of the upper cladding layer (202).

3. The mid-infrared waveguide gas sensor based on singular points according to claim 2, characterized in that: The first metal electrode (102) comprises a top metal electrode (208); a first insulating layer (205) and a second insulating layer (206) are symmetrically arranged on both sides of the top of the substrate (204); an upper cladding layer (202), a core layer (201) and a lower cladding layer (203) are located between the first insulating layer (205) and the second insulating layer (206); and the upper cladding layer (202), the core layer (201) and the lower cladding layer (203) are connected to the first insulating layer (205) and the second insulating layer (206) respectively; The top surface metal electrode (208) is arranged on the outer sides of the first insulating layer (205) and the second insulating layer (206), and the top surface metal electrode (208) is connected to the upper cladding layer (202).

4. The mid-infrared waveguide gas sensor based on singular points according to claim 3, characterized in that: The core layers (201) of the first racetrack-type microring resonator (101), the second racetrack-type microring resonator (103), the rectangular waveguide (105), the waveguide input tapered coupling port (106) and the waveguide output tapered coupling port (107) are all quantum well structures.

5. The mid-infrared waveguide gas sensor based on singular points according to claim 3, characterized in that: The materials of the upper cladding layer (202), the lower cladding layer (203) and the substrate (204) are all InP, the materials of the first insulating layer (205) and the second insulating layer (206) are all SiO2, and the materials of the bottom metal electrode (207) and the top metal electrode (208) are all Au.

6. The mid-infrared waveguide gas sensor based on singular points according to claim 1, characterized in that: The micro air chamber (108) is provided with an air chamber air inlet (109) and an air chamber air outlet (110).

7. The mid-infrared waveguide gas sensor based on singular points according to claim 6, characterized in that: The material of the micro air chamber (108) is polydimethylsiloxane.

8. A detection method for a mid-infrared waveguide gas sensor based on a singular point according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, coupling the light emitted by the mid-infrared laser to the waveguide input tapered coupling port (106), and coupling the light output from the waveguide output tapered coupling port (107) to the detector, collecting the output signal of the detector, recording the collected output signal and processing the output signal; S2: adjusting the current of the mid-infrared laser, scanning the quantum well gain band of the first racetrack-type microring resonator (101), monitoring the output signal of the sensor in real time, and obtaining the output spectrum of the sensor when no gain is added; S3: adjusting the current of the first metal electrode (102) to change the gain of the first racetrack-type microring resonator (101), adjusting the current of the second metal electrode (104) to change the resonance frequency of the second racetrack-type microring resonator (103), acquiring the sensor output spectrum, monitoring the degenerate state of the output signal resonance mode, and making the sensor reach a singular point; S4: introducing different concentrations of test gas into the gas chamber inlet (109) of the micro gas chamber (108) through the gas distribution system, the test gas changes the loss of the first racetrack-type microring resonator (101), collecting and processing the waste gas discharged from the gas chamber outlet (110), and recording the resonance mode splitting amounts corresponding to the different concentrations of the test gas; S5: Analyze the mid-infrared absorption characteristics of the gas to be tested by obtaining the resonance mode splitting amounts corresponding to the gas to be tested with different concentrations.

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