[1] Lifang GAO, Xu YANG, Yang SHU et al. Ionic liquid-based slab optical waveguide sensor for the detection of ammonia in human breath. Journal of Colloid and Interface Science, 512, 819-825(2018).

[2] Jiao CHEN, H HOKAZONO, D NAKASHIMA et al. Low loss silica high-mesa waveguide for infrared sensing. Japanese Journal of Applied Physics, 53, 022502(2014).

[3] Zhiwei LIU, Chuantao ZHENG, Tianyu ZHANG et al. Midinfrared sensor system based on tunable laser absorption spectroscopy for dissolved carbon dioxide analysis in the south china sea: system-level integration and deployment. Analytical Chemistry, 92, 8178-8185(2020).

[4] Fang SONG, Chuantao ZHENG, Wanhong YAN et al. Performance enhancement of methane detection using a novel self-adaptive mid-infrared absorption spectroscopy technique. IEEE Photonics Journal, 10, 6804512(2018).

[5] Fang SONG, Chuantao ZHENG, Wanhong YAN et al. Interband cascade laser based mid-infrared methane sensor system using a novel electrical-domain self-adaptive direct laser absorption spectroscopy (SA-DLAS). Optics Express, 25, 31876-31888(2017).

[6] Guoqiang ZHONG, Zhuo MA, Junbo WANG et al. Near-infrared tunable laser absorption spectroscopic acetylene sensor system using a novel three mirror-based, dense pattern gas cell. Sensors, 20, 1266(2020).

[7] Zhiwei LIU, Chuantao ZHENG, Chen CHEN et al. ICL-based mid-infrared carbon dioxide sensor system for deep-sea natural gas hydrate exploration. Optics Express, 27, 5598-5609(2019).

[8] Huawei JIN, Renzhi HU, Pinhua XIE et al. Study on the photoacoustic technology to simultaneous in-situ detection of the cavity ring-down spectrum for multi-optical parameters. IEEE Photonics Journal, 12, 6800711(2020).

[9] Yongbiao WENG, A TOUZEAU, H SODEMANN. Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers. Atmospheric Measurement Techniques, 13, 3167-3190(2020).

[10] Kaiyuan ZHENG, Chuantao ZHENG, Junhao LI et al. Near-infrared methane sensor system using off-axis integrated cavity output spectroscopy with novel dual-input dual-output coupling scheme for mode noise suppression. Sensors and Actuators B: Chemical, 308, 127674(2020).

[11] Kaiyuan ZHENG, Chuantao ZHENG, Ningning MA et al. Near-infrared broadband cavity-enhanced spectroscopic multigas sensor using a 1650 nm light emitting diode. ACS Sensors, 4, 1899-1908(2019).

[12] Lien HU, Chuantao ZHENG, Minghui ZHANG et al. Quartz-enhanced photoacoustic spectroscopic methane sensor system using a quartz tuning fork-embedded, double-pass and off-beam configuration. Photoacoustics, 18, 100174(2020).

[13] Lien HU, Chuantao ZHENG, Yu ZHANG et al. Compact all-fiber light-induced thermoelastic spectroscopy for gas sensing. Optics Letters, 45, 1894-1897(2020).

[14] Lien HU, Chuantao ZHENG, Jie ZHENG et al. Quartz tuning fork embedded off-beam quartz-enhanced photoacoustic spectroscopy. Optics Letters, 44, 2562-2565(2019).

[15] Haihong BAO, Yingzhen HONG, Wei JIN et al. Modeling and performance evaluation of in-line Fabry-Perot photothermal gas sensors with hollow-core optical fibers. Optics Express, 28, 5423-5435(2020).

[16] Yuechuan LIN, Fei LIU, Xiangge HE et al. Distributed gas sensing with optical fibre photothermal interferometry. Optics Express, 25, 31568-31585(2020).

[17] Xinyuan CHONG, Yujing ZHANG, Erwen LI et al. Surface-enhanced infrared absorption: pushing the frontier for on-chip gas sensing. ACS Sensors, 3, 230-238(2018).

[18] K KIM, Xinyuan CHONG, P B KREIDER et al. Plasmonics-enhanced metal-organic framework nanoporous films for highly sensitive near-infrared absorption. Journal of Materials Chemistry C, 3, 2763-2767(2015).

[19] S AKBAR, P DUTTA, C LEE. High-temperature ceramic gas sensors: a review. International Journal of Applied Ceramic Technology, 3, 302-311(2006).

[20] R SIEBERT, J MULLER. Infrared integrated optical evanescent field sensor for gas analysis part I: system design. Sensors and Actuators A: Physical, 119, 138-149(2005).

[21] R SIEBERT, J MULLER. Infrared integrated optical evanescent field sensor for gas analysis part Ⅱ: fabrication. Sensors and Actuators A: Physical, 119, 584-592(2005).

[22] W LAI, S CHAKRAVARTY, Xiaolong WANG et al. On-chip methane sensing by near-IR absorption signatures in a photonic crystal slot waveguide. Optics Letters, 36, 984-986(2011).

[23] E J ZHANG, Y MARTIN, J S ORCUTT et al. Monolithically integrated silicon photonic chip sensor for near-infrared trace-gas spectroscopy, 11010, 110100B(2019).

[24] C CHEN, D A MOHR, H CHOI et al. Waveguide-integrated compact plasmonic resonators for on-chip mid-infrared laser spectroscopy. Nano Letters, 18, 7601-7608(2018).

[25] D A MOHR, D YOO, C CHEN et al. Waveguide integrated mid-infrared plasmonics with high-efficiency coupling for ultracompact surface-enhanced infrared absorption spectroscopy. Optics Express, 26, 23540-23549(2018).

[26] C CHEN, S OH, M LI. Coupled-mode theory for plasmonic resonators integrated with silicon waveguides towards mid-infrared spectroscopic sensing. Optics Express, 28, 2020-2036(2020).

[27] A VASILIEV, A MALIK, M MUNEEB et al. On-chip mid-infrared photothermal spectroscopy using suspended silicon-on-insulator microring resonators. ACS Sensors, 1, 1301-1307(2016).

[28] R BHATTACHARJEE, N T KEJALAKSHMY, B M A RAHMAN. Design and optimization of an al doped ZnO in Si-slot for gas sensing. IEEE Photonics Journal, 10, 6802910(2018).

[29] B KUTILIKE, N KARI, Yuan ZHANG et al. Tetrahydroxyphenyl porphyrin membrane: a high-sensitivity optical waveguide gas sensor for NO2 detection. Measurement Science and Technology, 31, 055105(2020).

[30] A GUTIERREZ-ARROYO, E BAUDET, L BODIOU et al. Theoretical study of an evanescent optical integrated sensor for multipurpose detection of gases and liquids in the Mid-Infrared. Sensors and Actuators B: Chemical, 242, 842-848(2017).

[31] Yuxin LIANG, Qi LIU, Zhenlin WU et al. Cascaded-microrings biosensors fabricated on a polymer platform. Sensors, 19, 181(2019).

[32] Mingquan PI, Chuantao ZHENG, Ran BI et al. Design of a mid-infrared suspended chalcogenide/silica-on-silicon slot-waveguide spectroscopic gas sensor with enhanced light-gas interaction effect. Sensors and Actuators B: Chemical, 297, 126732(2019).

[33] J T ROBINSON, K PRESTON, O PAINTER et al. First-principle derivation of gain in high-index-contrast waveguides. Optics Express, 16, 16659-16669(2008).

[34] Mingquan PI, Chuantao ZHENG, Jialin JI et al. Surface-enhanced infrared absorption spectroscopic chalcogenide waveguide sensor using a silver island film. ACS Applied Materials & Interfaces, 13, 32555-32563(2021).

[35] K M YOO, J MIDKIFF, A ROSTAMIAN et al. InGaAs membrane waveguide: a promising platform for monolithic integrated mid-infrared optical gas sensor. ACS Sensors, 5, 861-869(2020).

[36] A GERVAIS, P JEAN, Wei SHI et al. Design of slow-light subwavelength grating waveguides for enhanced on-chip methane sensing by absorption spectroscopy. IEEE Journal of Selected Topics in Quantum Electronics, 25, 5200308(2019).

[37] Mingquan PI, Chuantao ZHENG, Zihang PENG et al. Theoretical study of microcavity-enhanced absorption spectroscopy for mid-infrared methane detection using a chalcogenide/silica-on-fluoride horizontal slot-waveguide racetrack resonator. Optics Express, 28, 21432-21446(2020).

[38] C J SMITH, R SHANKAR, M LADERER et al. Sensing nitrous oxide with QCL-coupled silicon-on-sapphire ring resonators. Optics Express, 23, 5491-5499(2015).

[39] Yu CHEN, Hongtao LIN, Juejun HU et al. Heterogeneously integrated silicon photonics for the mid-infrared and spectroscopic sensing. ACS Nano, 8, 6955-6961(2014).

[40] A GUTIERREZ-ARROYO, E BAUDET, L BODIOU et al. Optical characterization at 7.7 μm of an integrated platform based on chalcogenide waveguides for sensing applications in the mid-infrared. Optics Express, 24, 23109-23117(2016).

[41] B KUMARI, A BARH, R K VARSHNEY et al. Silicon-on-nitride slot waveguide: a promising platform as mid-IR trace gas sensor. Sensors and Actuators B: Chemical, 236, 759-764(2016).

[42] R SHANKAR, I BULU, M LONCAR. Integrated high-quality factor silicon-on-sapphire ring resonators for the mid-infrared. Applied Physics Letters, 102, 051108(2013).

[43] Yuewang HUANG, S K KALYONCU, Qiancheng ZHAO et al. Silicon-on-sapphire waveguides design for mid-IR evanescent field absorption gas sensors. Optics Communications, 313, 186-194(2014).

[44] N SINGH, A CASAS-BEDOYA, D D HUDSON et al. Mid-IR absorption sensing of heavy water using a silicon-on-sapphire waveguide. Optics Letters, 41, 5776-5779(2016).

[45] Pan MA, D CHOI, Yi YU et al. High Q factor chalcogenide ring resonators for cavity-enhanced MIR spectroscopic sensing. Optics Express, 23, 19969-19979(2015).

[46] J CHARRIER, M BRANDILY, H LHERMITE et al. Evanescent wave optical micro-sensor based on chalcogenide glass. Sensors and Actuators B: Chemical, 173, 468-476(2012).

[47] Z HAN, P LIN, V SINGH et al. On-chip mid-infrared gas detection using chalcogenide glass waveguide. Applied Physics Letters, 108, 141106(2016).

[48] R SINGH, P SU, L KIMERLING et al. Towards on-chip mid infrared photonic aerosol spectroscopy. Applied Physics Letters, 113, 231107(2018).

[49] Qingyang DU, Zhengqian LUO, Huikai ZHONG et al. Chip-scale broadband spectroscopic chemical sensing using an integrated supercontinuum source in a chalcogenide glass waveguide. Photonics Research, 6, 506-510(2018).

[50] P SU, Z HAN, D KITA et al. Monolithic on-chip mid-IR methane gas sensor with waveguide-integrated detector. Applied Physics Letters, 114, 051103(2019).

[51] E RYCKEBOER, R BOCKSTAELE, M VANSLEMBROUCK et al. Glucose sensing by waveguide-based absorption spectroscopy on a silicon chip. Biomedical Optics Express, 5, 1636-1648(2014).

[52] L TOMBEZ, E J ZHANG, J S ORCUTT et al. Methane absorption spectroscopy on a silicon photonic chip. Optica, 4, 1322-1325(2017).

[53] A KATIYI, A KARABCHEVSKY. Si nanostrip optical waveguide for on-chip broadband molecular overtone spectroscopy in near-infrared. ACS Sensors, 3, 618-623(2018).

[54] D M KITA, J MICHON, J J HU. A packaged, fiber-coupled waveguide-enhanced Raman spectroscopic sensor. Optics Express, 28, 14963-14972(2020).

[55] A NITKOWSKI, A BAEUMNER, M LIPSON. On-chip spectrophotometry for bioanalysis using microring resonators. Biomedical Optics Express, 2, 271-277(2011).

[56] R SINGH, D H MA, L KIMERLING et al. Chemical characterization of aerosol particles using on-chip photonic cavity enhanced spectroscopy. ACS Sensors, 4, 571-577(2019).

[57] D M KITA, J MICHON, S G JOHNSON et al. Are slot and sub-wavelength grating waveguides better than strip waveguides for sensing？. Optica, 5, 1046-1054(2018).

[58] P T LIN, S W KWOK, H G LIN et al. Mid-infrared spectrometer using opto-nanofluidic slot-waveguide for label-free on-chip chemical sensing. Nano Letters, 14, 231-238(2014).

[59] P T LIN, H G LIN, Zhaohong HAN et al. Label-free glucose sensing using chip-scale mid-infrared integrated photonics. Advanced Optical Materials, 4, 1755-1759(2016).

[60] Qiankun LIU, J M RAMIREZ, V VAKARIN et al. Mid-infrared sensing between 5.2 and 6.6 µm wavelengths using Ge-rich SiGe waveguides [Invited]. Optical Materials Express, 8, 1305-1312(2018).

[61] Yingying QIAO, Jifang TAO, C CHEN et al. A miniature on-chip methane sensor based on an ultra-low loss waveguide and a micro-ring resonator filter. Micromachines, 8, 160(2017).

[62] M A BUTT, S A DEGTYAREV, S N KHONINA et al. An evanescent field absorption gas sensor at mid-IR 3.39 μm wavelength. Journal of Modern Optics, 64, 1892-1897(2017).

[63] M A BUTT, S N KHONINA, N L KAZANSKIY. Enhancement of evanescent field ratio in a silicon strip waveguide by incorporating a thin metal film. Laser Physics, 29, 076202(2019).

[64] Yu XIN, G PANDRAUD, Yongmeng ZHANG et al. Single-mode tapered vertical su-8 waveguide fabricated by e-beam lithography for analyte sensing. Sensors, 19, 3383(2019).

[65] Tianye HUANG, Guizhen XU, Jianxing PAN et al. Theoretical study of bicharacteristic waveguide for fundamental-mode phase-matched SHG from MIR to NIR. Optics Express, 27, 15236-15250(2019).

[66] N KOOMPAI, P LIMSUWAN, R X LE et al. Analysis of Si3N4 waveguides for on-chip gas sensing by optical absorption within the mid-infrared region between 2.7 and 3.4 µm. Results in Physics, 16, 102957(2020).

[67] R ZEGADI, N LORRAIN, L BODIOU et al. Enhanced mid-infrared gas absorption spectroscopic detection using chalcogenide or porous germanium waveguides. Journal of Optics, 23, 035102(2021).

[68] F DELL'OLIO, V M N PASSARO. Optical sensing by optimized silicon slot waveguides. Optics Express, 15, 4977-4993(2007).

[69] M Y ELSAYED, Y ISMAIL, M A SWILLAM. Semiconductor plasmonic gas sensor using on-chip infrared spectroscopy. Applied Physics A Materials Science & Processing, 123, 113(2018).

[70] M A BUTT, S N KHONINA, N L KAZANSKIY. Silicon on silicon dioxide slot waveguide evanescent field gas absorption sensor. Journal of Modern Optics, 65, 174-178(2018).

[71] B KUMARI, R K VARSHNEY, B P PAL. Design of chip scale silicon rib slot waveguide for sub-ppm detection of N2O gas at mid-IR band. Sensors and Actuators B: Chemical, 255, 3409-3416(2018).

[72] Yingying QIAO, Jifang TAO, Jifang QIU et al. Sensitive and ultrasmall sample volume gas sensor based on a sealed slot waveguide. Applied Optics, 58, 4708-4713(2019).

[73] Yuefeng WANG, Weiwei CHEN, Pengjun WANG et al. Ultra-high-power-confinement-factor integrated mid-infrared gas sensor based on the suspended slot chalcogenide glass waveguide. Sensors and Actuators B: Chemical, 347, 130466(2021).

[74] N KOOMPAI, P CHAISAKUL, P LIMSUWAN et al. Design and simulation investigation of Si3N4 photonics circuits for wideband on-chip optical gas sensing around 2 µm optical wavelength. Sensors, 21, 2513(2021).

[75] V CHANDRA, R RANJAN. Performance analysis of different slot waveguide structures for evanescent field based gas sensor applications. Optical and Quantum Electronics, 53, 457(2021).

[76] Yanan ZHANG, Yong ZHAO, Qi WANG. Optimizing the slow light properties of slotted photonic crystal waveguide and its application in a high-sensitivity gas sensing system. Measurement Science and Technology, 24, 105109(2013).

[77] R JANNESARI, C RANACHER, C CONSANI et al. Sensitivity optimization of a photonic crystal ring resonator for gas sensing applications. Sensors and Actuators A: Physical, 264, 347-351(2017).

[78] J FLUECKIGER, S SCHMIDT, V DONZELLA et al. Sub-wavelength grating for enhanced ring resonator biosensor. Optics Express, 24, 15672-15686(2016).

[79] Guizhen XU, Jin WANG, Qizheng JI et al. Design and analysis of slow-light Bloch slot waveguides for on-chip gas sensing. Journal of the Optical Society of America B, 37, 257-263(2020).

[80] L STERN, B DESIATOV, I GOYKHMAN et al. Nanoscale light-matter interactions in atomic cladding waveguides. Nature Communications, 4, 1548(2013).

[81] C RANACHER, C CONSANI, N VOLLERT et al. Characterization of evanescent field gas sensor structures based on silicon photonics. IEEE Photonics Journal, 10, 2700614(2018).

[82] C RANACHER, C CONSANI, A TORTSCHANOFF et al. Mid-infrared absorption gas sensing using a silicon strip waveguide. Sensors and Actuators A: Physical, 277, 117-123(2018).

[83] C CONSANI, C RANACHER, A TORTSCHANOFF et al. Mid-infrared photonic gas sensing using a silicon waveguide and an integrated emitter. Sensors and Actuators B: Chemical, 274, 60-65(2018).

[84] C RANACHER, C CONSANI, U HEDENIG et al. A photonic silicon waveguide gas sensor using evanescent-wave absorption, 1-3(2016).

[85] H D AL, Y KARANTH, Junchao ZHOU et al. Surface functionalization utilizing mesoporous silica nanoparticles for enhanced evanescent-field mid-infrared waveguide Gas sensing. Coatings, 11, 118(2021).

[86] Mingquan PI, Chuantao ZHENG, Huan ZHAO et al. Mid-infrared ChG-on-MgF2 waveguide gas sensor based on wavelength modulation spectroscopy. Optics Letters, 46, 4797-4800(2021).

[87] Mingquan PI, Yijun HUANG, Huan ZHAO et al. Theoretical and experimental investigation of on-chip mid-infrared chalcogenide waveguide CH4 sensor based on wavelength modulation spectroscopy. Sensors and Actuators B: Chemical, 362, 131782(2022).

[88] F OTTONELLO-BRIANO, C ERRANDO-HERRANZ, H RODJEGARD et al. Carbon dioxide absorption spectroscopy with a mid-infrared silicon photonic waveguide. Optics Letters, 45, 109-112(2020).

[89] M VLK, A DATTA, S ALBERTI et al. Extraordinary evanescent field confinement waveguide sensor for mid-infrared trace gas spectroscopy. Light: Science & Applications, 10, 26(2021).

[90] T H STIEVATER, M W PRUESSNER, D PARK et al. Trace gas absorption spectroscopy using functionalized microring resonators. Optics Letters, 39, 969-972(2014).

[91] S CHAKRAVARTY, J MIDKIFF, K YOO et al. Monolithic integration of quantum cascade laser, quantum cascade detector, and subwavelength waveguides for mid-infrared integrated gas sensing, 109261V(2019).

[92] Weixin LIU, Yiming MA, Yuhua CHANG et al. Suspended silicon waveguide platform with subwavelength grating metamaterial cladding for long-wave infrared sensing applications. Nanophotonics, 10, 1861-1870(2021).

[93] A ROSTAMIAN, E MADADI-KANDJANI, H DALIR et al. Towards lab-on-chip ultrasensitive ethanol detection using photonic crystal waveguide operating in the mid-infrared. Nanophotonics, 10, 1675-1682(2021).

[94] Weixin LIU, Yiming MA, Xinmiao LIU et al. Larger-than-unity external optical field confinement enabled by metamaterial-assisted comb waveguide for ultrasensitive long-wave infrared gas spectroscopy. Nano Letters, 22, 6112-6120(2022).