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

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

[3] LIU Zhiwei, ZHENG Chuantao, ZHANG Tianyu 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[J]. Analytical Chemistry, 92, 8178-8185(2020).

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

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

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

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

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

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

[10] ZHENG Kaiyuan, ZHENG Chuantao, LI Junhao 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[J]. Sensors and Actuators B: Chemical, 308, 127674(2020).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[37] PI Mingquan, ZHENG Chuantao, PENG Zihang 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[J]. Optics Express, 28, 21432-21446(2020).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[66] KOOMPAI N, LIMSUWAN P, LE R X 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[J]. Results in Physics, 16, 102957(2020).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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