Multi-channel Raman scattering spectrum gas sensing system based on grating coupler array

Abstract

The invention provides a multichannel Raman scattering spectrum gas sensing system based on a grating coupler array, and particularly relates to the technical field of gas analysis and measurement. The multi-channel near-infrared top emitting laser array is incident to the surface of the organic polymer film at a small angle, laser and gas to be detected interact to generate spontaneous Raman scattering light, the grating coupler array realizes multi-channel and high-efficiency collection of the Raman scattering light, and the scattering light is coupled to the transmission waveguide, so that the Raman scattering light is transmitted to the surface of the organic polymer film. The transmission waveguide is coupled with the optical fiber and is transmitted to the Raman spectrometer for detection, the data processing module extracts gas measurement information, and the main control module overall plans all the modules to work cooperatively. The laser, the transmission waveguide, the data analysis module and the like are integrated to form a multi-channel, integrated and low-power-consumption Raman scattering spectrum gas measurement system, and the Raman scattering spectrum gas measurement system has the advantages of high detection efficiency, high stability, small size and high adaptability, and can be widely applied to scenes such as gas analysis and environment monitoring.

Description

Technical Field

[0001] This invention relates to the field of gas analysis and measurement technology, and more specifically, to a multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array. Background Technology

[0002] Raman scattering spectroscopy gas sensing technology illuminates the analyte gas with incident light of a fixed wavelength, detects the Raman scattered light, and identifies the components of the analyte gas based on characteristic spectra and changes in light intensity, thus quantitatively measuring the content of each component. Due to its advantages of being label-free and enabling simultaneous detection of multiple gases, Raman scattering spectroscopy gas sensing technology is widely used in gas analysis and measurement. However, existing Raman gas sensing systems mostly employ discrete component combinations, resulting in large system sizes, poor portability, and inability to adapt to miniaturized gas detection scenarios. Furthermore, many systems rely on lenses to collect Raman scattered light, leading to low coupling efficiency and difficulty in achieving multi-channel parallel collection.

[0003] Furthermore, existing organic polymer films used for gas detection are mostly used only as gas enrichment materials, and their role in spatial distribution modulation and coupling efficiency improvement of Raman scattered light has not been fully utilized. Therefore, there is an urgent need for an integrated gas sensing system with a clear structure, well-defined physical mechanism, and the ability to achieve efficient collection of multi-channel, low-crosstalk Raman scattered light. Summary of the Invention

[0004] To address the problems in the background art, the present invention provides a multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array, thereby overcoming the deficiencies of existing gas sensing systems.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array includes: The system comprises a first near-infrared top-emitting laser, a second near-infrared top-emitting laser, a third near-infrared top-emitting laser, an organic polymer thin film, a multi-channel Raman scattering gas sensor based on a grating coupler array, a thermoelectric cooler, an optical fiber, a Raman filter, a Raman spectrometer, a data processing module, a main control module, a laser driver module, and a temperature control module. The multi-channel Raman scattering spectroscopy gas sensor based on a grating coupler array includes a first grating coupler, a second grating coupler, a third grating coupler, a first end-face coupler, a second end-face coupler, a third end-face coupler, and a transmission waveguide. The first, second, and third near-infrared top-emitting lasers operate under the coordinated control of the laser driving module and the temperature control module, and their emitted lasers all emit lasers at the same fixed tilt angle relative to the normal direction of the organic polymer film. i Incident onto the surface of the organic polymer film; The organic polymer film is exposed to the gas environment to be tested. Its interior has a connected microporous structure for adsorbing and enriching the gas molecules to be tested, so that the excitation laser and the gas to be tested can fully interact on the surface of the organic polymer film and in its near-field region to generate spontaneous Raman scattering light. The first grating coupler, the second grating coupler, and the third grating coupler are respectively disposed on one side of the organic polymer film, for synchronously and multi-channel collecting of the Raman scattered light in space, and coupling the Raman scattered light into the transmission waveguide respectively; The output end of the transmission waveguide is connected to the optical fiber via a first end-face coupler, a second end-face coupler, and a third end-face coupler, respectively. The output end of the optical fiber is connected to a Raman filter and a Raman spectrometer in sequence. The Raman spectrometer is used to perform spectral detection on the Raman scattered light. The detection result is transmitted to the data processing module and fed back to the main control module. Among them, for the first i A grating coupler with a grating period Λ i The laser tilted incident angle i The Raman scattering center wavelength corresponding to this channel l R,i and the effective refractive index of the transmission waveguide for Raman scattered light n eff The following phase matching relationship is satisfied between them: ,in: l R,i For the first i The Raman scattering center wavelength corresponding to each grating coupler i To excite the laser at a tilted incident angle relative to the normal direction of the organic polymer film, n eff Λ is the effective refractive index of the transmission waveguide for the Raman scattered light. i For the first i The grating period of a grating coupler m For grating diffraction orders, i =1,2,3; so that the Raman scattered light can be efficiently coupled into the transmission waveguide by the corresponding grating coupler only when the propagation direction and wavelength of the Raman scattered light simultaneously satisfy the above phase matching relationship, thereby forming a cooperative decoupling based on wavelength and spatial direction between different channels; The equivalent optical thickness of the organic polymer film in the Raman scattering band h The following relationship is satisfied between the wavelength of the Raman scattering center: ,in: h This represents the equivalent optical thickness of the organic polymer film within the excitation region. n p The equivalent refractive index of the organic polymer film 11 in the Raman scattering band is given by . q The integer is non-negative, so that the organic polymer film forms near-field enhancement and directional radiation modulation in the Raman scattering band, thereby redistributing the main energy of the Raman scattered light to an angle range consistent with the phase matching direction of the grating coupler array, realizing efficient and low crosstalk integrated collection of multi-channel Raman scattered light.

[0006] Preferably, the organic polymer film is a polyphthalamide film.

[0007] Preferably, the Raman filter is installed between the optical fiber and the Raman spectrometer to filter out Rayleigh scattered light reflected by the organic polymer film, allowing only Stokes Raman scattered light and anti-Stokes Raman scattered light to enter the Raman spectrometer.

[0008] The beneficial effects of this invention are as follows: (1) This invention achieves selective coupling of Raman scattered light by introducing a phase matching relationship between Raman scattering wavelength, laser incident angle and grating period, thereby improving the effective collection efficiency of Raman scattered light.

[0009] (2) By setting different grating periods for different grating couplers, different Raman scattering channels can achieve coordinated decoupling in spatial propagation direction and wavelength, which significantly reduces crosstalk between multiple channels.

[0010] (3) By limiting the equivalent optical thickness of the organic polymer film, the present invention enables it to form near-field enhancement and directional radiation modulation in the Raman scattering band, thereby simultaneously improving the Raman scattering signal intensity and coupling efficiency.

[0011] (4) This invention integrates laser excitation, gas enrichment, Raman generation and on-chip photonic coupling into a system-level collaborative design, avoiding reliance on the performance improvement of a single device and achieving optimization of overall detection performance.

[0012] (5) The present invention uses grating coupler array and on-chip transmission waveguide to replace traditional free space optical devices, which significantly reduces the system size and improves system stability and engineering feasibility. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the structure of a multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array provided in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the simulation optimization results of the structural parameters of a single-channel grating coupler.

[0015] The attached figures are labeled as follows: 1-First near-infrared top-emitting laser, 2-Second near-infrared top-emitting laser, 3-Third near-infrared top-emitting laser, 4-First grating coupler, 5-Second grating coupler, 6-Third grating coupler, 7-First end-face coupler, 8-Second end-face coupler, 9-Third end-face coupler, 10-Transmission waveguide, 11-Organic polymer thin film, 12-Multi-channel Raman scattering spectroscopy gas sensor based on grating coupler array, 13-Thermoelectric cooler, 14-Fiber optic cable, 15-Raman filter, 16-Raman spectrometer, 17-Data processing module, 18-Main control module, 19-Laser driver module, 20-Temperature control module. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] See Figure 1The multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array includes a first near-infrared top-emitting laser 1, a second near-infrared top-emitting laser 2, a third near-infrared top-emitting laser 3, an organic polymer film 11, a multi-channel Raman scattering spectroscopy gas sensor based on a grating coupler array 12, a thermoelectric cooler 13, an optical fiber 14, a Raman filter 15, a Raman spectrometer 16, a data processing module 17, a main control module 18, a laser drive module 19, and a temperature control module 20; the multi-channel Raman scattering spectroscopy gas sensor 12 based on a grating coupler array includes: a first grating coupler 4, a second grating coupler 5, a third grating coupler 6, a first end-face coupler 7, a second end-face coupler 8, a third end-face coupler 9, and a transmission waveguide 10.

[0019] In this embodiment of the invention, the first near-infrared top-emitting laser 1, the second near-infrared top-emitting laser 2, and the third near-infrared top-emitting laser 3 are all connected to the organic polymer film 11; the organic polymer film 11 is connected to the input ends of the first grating coupler 4, the second grating coupler 5, and the third grating coupler 6; the output ends of the first grating coupler 4, the second grating coupler 5, and the third grating coupler 6 are connected to the input ends of the transmission waveguide 10; the output end of the transmission waveguide 10 is connected to the input end of the optical fiber 14; the output end of the optical fiber 14 is connected to the input end of the Raman filter 15; the output end of the Raman filter 15 is connected to the input end of the Raman spectrometer 16; and the output end of the Raman spectrometer 16 is connected to the input end of the data processing module 17.

[0020] The main control module 18 is connected to the data processing module 17, the laser driver module 19 and the temperature control module 20 respectively; the temperature control module 20 is connected to the thermoelectric cooler 13; the thermoelectric cooler 13 is connected to the first near-infrared top-emitting laser 1, the second near-infrared top-emitting laser 2 and the third near-infrared top-emitting laser 3.

[0021] By way of example and not limitation, in this embodiment of the invention, the first grating coupler 4, the second grating coupler 5, the third grating coupler 6, the first end face coupler 7, the second end face coupler 8, the third end face coupler 9, and the transmission waveguide 10 are all integrated on the SiO2 substrate.

[0022] By way of example and not limitation, in this embodiment of the invention, a first near-infrared top-emitting laser 1, a second near-infrared top-emitting laser 2, a third near-infrared top-emitting laser 3, an organic polymer film 11, a multi-channel Raman scattering spectroscopy gas sensor 12 based on a grating coupler array, a thermoelectric cooler 13, and an optical fiber 14 are encapsulated in a gas chamber.

[0023] The first near-infrared top-emitting laser 1, the second near-infrared top-emitting laser 2, and the third near-infrared top-emitting laser 3 operate under the coordinated control of the laser driving module 19 and the temperature control module 20. Their emitted lasers are all incident on the surface of the organic polymer film 11 at the same fixed tilt angle θ relative to the normal direction of the organic polymer film 11.

[0024] The organic polymer film 11 is exposed to the gas environment to be tested. Its interior has a connected microporous structure for adsorbing and enriching the gas molecules to be tested, so that the excitation laser and the gas to be tested can fully interact on the surface of the organic polymer film 11 and in its near-field region to generate spontaneous Raman scattering light.

[0025] The first grating coupler 4, the second grating coupler 5, and the third grating coupler 6 are respectively disposed on one side of the organic polymer film 11, and are used to synchronously and multi-channel collect Raman scattered light in space, and couple the Raman scattered light into the transmission waveguide 10 respectively.

[0026] The output end of the transmission waveguide 10 is connected to the optical fiber 14 via the first end-face coupler 7, the second end-face coupler 8 and the third end-face coupler 9 respectively. The output end of the optical fiber 14 is connected to the Raman filter 15 and the Raman spectrometer 16 in sequence. The Raman spectrometer is used to perform spectral detection on the Raman scattered light. The detection result is transmitted to the data processing module 17 and fed back to the main control module 18.

[0027] Among them, for the first i A grating coupler with a grating period Λ i Laser tilt angle of incidence i The Raman scattering center wavelength corresponding to this channel l R,i and the effective refractive index of the transmission waveguide for Raman scattered light n eff The following phase matching relationship is satisfied between them: ,in: l R,i For the first i The Raman scattering center wavelength corresponding to each grating coupler i To excite the laser at a tilted incident angle relative to the normal direction of the organic polymer film, n eff Λ is the effective refractive index of the transmission waveguide for Raman scattered light. i For the first i The grating period of a grating coupler m For grating diffraction orders, i=1,2,3; so that Raman scattered light can be efficiently coupled into the transmission waveguide by the corresponding grating coupler only when the propagation direction and wavelength of Raman scattered light simultaneously satisfy the above phase matching relationship, thereby forming a cooperative decoupling based on wavelength and spatial direction between different channels; Equivalent optical thickness of organic polymer thin films in the Raman scattering band h The following relationship exists between the wavelength and the center wavelength of Raman scattering: ,in: h This represents the equivalent optical thickness of the organic polymer film within the excitation region. n p The equivalent refractive index of the organic polymer film 11 in the Raman scattering band is given by . q The integer is non-negative, so that the organic polymer film can form near-field enhancement and directional radiation modulation in the Raman scattering band, thereby redistributing the main energy of the Raman scattered light to an angle range consistent with the phase matching direction of the grating coupler array, realizing efficient and low crosstalk integrated collection of multi-channel Raman scattered light.

[0028] Preferably, the organic polymer film is a polyphthalamide film; the Raman filter is used to filter out Rayleigh scattered light reflected by the organic polymer film, allowing only Stokes Raman scattered light and anti-Stokes Raman scattered light to enter the Raman spectrometer.

[0029] See Figure 2 In another embodiment of the present invention, a schematic diagram of the simulation optimization results of the single-channel grating coupler structural parameters of the multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array is shown below. Figure 2 As shown. Considering manufacturing process tolerances, under the premise of a 30° incident angle, the grating incident position is... x =50 μm, grating spacing p =7.4μm, duty cycle d When the coefficient of performance is 0.445947, the coupling efficiency of the grating coupler reaches 39.37%.

[0030] It is worth noting that in existing multi-channel Raman detection systems, spatial and spectral crosstalk easily occurs between different detection channels, affecting detection accuracy. Polymer films are usually only used as gas enrichment materials and do not modulate the spatial distribution and coupling efficiency of Raman scattered light. Integrated photonic Raman systems lack a holistic and coordinated design from laser incidence, Raman generation, photon collection to on-chip transmission, resulting in system performance improvements relying on the optimization of single devices. This invention, however, introduces a phase-matching relationship between the Raman scattering center wavelength, laser tilt angle, grating period, and effective refractive index of the transmission waveguide. This ensures that Raman scattered light can only be efficiently coupled into the transmission waveguide by the corresponding grating coupler when the Raman scattered light simultaneously meets specific propagation direction and wavelength conditions. The Raman scattered light collection process is upgraded from the traditional geometric alignment method to a selective coupling method based on wave vector matching, significantly improving the effective collection efficiency of Raman scattered light.

[0031] This invention assigns different grating couplers to different grating periods and establishes a one-to-one correspondence with different Raman scattering center wavelengths, enabling simultaneous differentiation of each channel in terms of spatial propagation direction and spectral characteristics. This collaborative decoupling mechanism physically suppresses crosstalk between channels, reduces the complexity of back-end signal processing, and improves the accuracy and stability of multi-channel Raman detection. Simultaneously, by ensuring the equivalent optical thickness of the organic polymer film meets certain conditions, an equivalent optical path condition of an odd multiple of a quarter wavelength is formed within the film, thereby creating a near-field enhancement region for Raman scattering on the film surface and directing the Raman scattering light towards a direction that satisfies the grating phase-matching condition. This invention achieves efficient collection and transmission of Raman scattering light through a grating coupler array and on-chip transmission waveguides, avoiding the use of traditional lens or mirror structures and significantly reducing system size. Combined with a temperature control module for stable control of the laser array, the system maintains high detection sensitivity while possessing good long-term stability and engineering feasibility.

[0032] The embodiments described above are merely preferred embodiments of the present invention. The terms "in one embodiment," "in another embodiment," "in yet another embodiment," or "in still another embodiment" used in this specification all refer to one or more of the same or different embodiments according to this disclosure. Ordinary variations and substitutions made by those skilled in the art within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array, characterized in that, include: The system comprises a first near-infrared top-emitting laser, a second near-infrared top-emitting laser, a third near-infrared top-emitting laser, an organic polymer thin film, a multi-channel Raman scattering gas sensor based on a grating coupler array, a thermoelectric cooler, an optical fiber, a Raman filter, a Raman spectrometer, a data processing module, a main control module, a laser driver module, and a temperature control module. The multi-channel Raman scattering spectroscopy gas sensor based on a grating coupler array includes a first grating coupler, a second grating coupler, a third grating coupler, a first end-face coupler, a second end-face coupler, a third end-face coupler, and a transmission waveguide. The first, second, and third near-infrared top-emitting lasers operate under the coordinated control of the laser driving module and the temperature control module, and their emitted lasers all emit lasers at the same fixed tilt angle relative to the normal direction of the organic polymer film. θ Incident onto the surface of the organic polymer film; The organic polymer film is exposed to the gas environment to be tested. Its interior has a connected microporous structure for adsorbing and enriching the gas molecules to be tested, so that the excitation laser and the gas to be tested can fully interact on the surface of the organic polymer film and in its near-field region to generate spontaneous Raman scattering light. The first grating coupler, the second grating coupler, and the third grating coupler are respectively disposed on one side of the organic polymer film, for synchronously and multi-channel collecting of the Raman scattered light in space, and coupling the Raman scattered light into the transmission waveguide respectively; The output end of the transmission waveguide is connected to the optical fiber via a first end-face coupler, a second end-face coupler, and a third end-face coupler, respectively. The output end of the optical fiber is connected to a Raman filter and a Raman spectrometer in sequence. The Raman spectrometer is used to perform spectral detection on the Raman scattered light. The detection result is transmitted to the data processing module and fed back to the main control module. Among them, for the first i A grating coupler with a grating period Λ i The fixed tilt angle θ and the effective refractive index of the transmission waveguide for Raman scattered light n eff The following phase matching relationship is satisfied between them: ,in: λ R,i For the first i The Raman scattering center wavelength corresponding to each grating coupler n eff Λ is the effective refractive index of the transmission waveguide for the Raman scattered light. i For the first i The grating period of a grating coupler m For grating diffraction orders, i =1,2,3; The equivalent optical thickness of the organic polymer film in the Raman scattering band h The following relationship exists between the wavelength and the center wavelength of Raman scattering: ,in: n p is the equivalent refractive index of the organic polymer film in the Raman scattering band. q It is a non-negative integer.

2. The multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array according to claim 1, characterized in that, The organic polymer film is a polyphthalamide film.

3. The multi-channel Raman scattering spectroscopy gas sensing system based on a grating coupler array according to claim 1, characterized in that, The Raman filter is installed between the optical fiber and the Raman spectrometer to filter out Rayleigh scattered light reflected by the organic polymer film, allowing only Stokes Raman scattered light and anti-Stokes Raman scattered light to enter the Raman spectrometer.

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