[1] Soref R. Mid-infrared photonics in silicon and germanium[J]. Nature Photonics, 4, 495-497(2010). http://www.nature.com/articles/nphoton.2010.171

[2] Hu J, Meyer J R, Richardson K et al. Feature issue introduction: mid-IR photonic materials[J]. Optical Materials Express, 3, 1571-1575(2013). http://www.opticsinfobase.org/abstract.cfm?uri=ome-3-9-1571

[3] Soref R A, Emelett S J, Buchwald W R. Silicon waveguided components for the long-wave infrared region[J]. Journal of Optics A: Pure and Applied Optics, 8, 840-848(2006). http://dialnet.unirioja.es/servlet/articulo?codigo=2155950

[4] Jalali B, Fathpour S. Silicon photonics[J]. Journal of Lightwave Technology, 24, 4600-4615(2006).

[5] Soref R. The past, present, and future of silicon photonics[J]. IEEE Journal of Selected Topics in Quantum Electronics, 12, 1678-1687(2006).

[6] Zheng X, Liu Y. Large-scale photonic integration technologies based on multi-project wafer flow sheet[J]. Laser & Optoelectronics Progress, 54, 050001(2017).

[7] Soref R. Group IV photonics for the mid infrared[J]. Proceedings of SPIE, 8629, 862902(2013).

[8] Tittel F K, Richter D, Fried A. Mid-infrared laser applications in spectroscopy[J]. Solid-State Mid-Infrared Laser Sources, 458-529(2003).

[9] Willer U, Saraji M, Khorsandi A et al. Near- and mid-infrared laser monitoring of industrial processes, environment and security applications[J]. Optics and Lasers in Engineering, 44, 699-710(2006).

[10] Werle P, Slemr F, Maurer K et al. Near- and mid-infrared laser-optical sensors for gas analysis[J]. Optics and Lasers in Engineering, 37, 101-114(2002). http://www.sciencedirect.com/science/article/pii/S0143816601000926

[11] Sieger M, Mizaikoff B. Toward on-chip mid-infrared sensors[J]. Analytical Chemistry, 88, 5562-5573(2016).

[12] Spott A, Liu Y, Baehr-Jones T et al. Silicon waveguides and ring resonators at 5.5 μm[J]. Applied Physics Letters, 97, 213501(2010).

[13] Wong C Y, Cheng Z Z, Chen X et al. Characterization of mid-infrared silicon-on-sapphire microring resonators with thermal tuning[J]. IEEE Photonics Journal, 4, 1095-1102(2012).

[14] 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).

[15] Griffith A G. Lau R K W, Cardenas J, et al. Silicon-chip mid-infrared frequency comb generation[J]. Nature Communications, 6, 6299(2015).

[16] Miller S A, Yu M J, Ji X C et al. Low-loss silicon platform for broadband mid-infrared photonics[J]. Optica, 4, 707-712(2017).

[17] Cheng Z Z, Chen X, Wong C Y et al. Mid-infrared suspended membrane waveguide and ring resonator on silicon-on-insulator[J]. IEEE Photonics Journal, 4, 1510-1519(2012).

[18] Xia Y, Qiu C Y, Zhang X Z et al. Suspended Si ring resonator for mid-IR application[J]. Optics Letters, 38, 1122-1124(2013).

[19] Zhang Z C, Ng G I, Hu T et al. Mid-infrared sensor based on a suspended microracetrack resonator with lateral subwavelength-grating metamaterial cladding[J]. IEEE Photonics Journal, 10, 1-8(2018).

[20] Zhang Z C, Ng G I, Hu T et al. Suspended microracetrack resonator with lateral sub-wavelength-grating metamaterial cladding for mid-infrared sensing applications[J]. ITM Web of Conferences, 17, 02005(2018).

[21] Kang J, Takagi S, Takenaka M. Design and characterization of Ge passive waveguide components on Ge-on-insulator wafer for mid-infrared photonics[J]. Japanese Journal of Applied Physics, 57, 042202(2018).

[22] Xiao T H, Zhao Z Q, Zhou W et al. Mid-infrared high-Q germanium microring resonator[J]. Optics Letters, 43, 2885-2888(2018).

[23] Ramírez J M, Vakarin V, Liu Q et al. Ge-rich graded-index Si1-xGex racetrack resonators for long-wave infrared photonics[J]. Proceedings of SPIE, 1092, 109261U(2019).

[24] Lin H T, Li L, Zou Y et al. Demonstration of high-Q mid-infrared chalcogenide glass-on-silicon resonators[J]. Optics Letters, 38, 1470-1472(2013).

[25] Radosavljevic S, Beneitez N T, Katumba A et al. Mid-infrared Vernier racetrack resonator tunable filter implemented on a germanium on SOI waveguide platform[J]. Optical Materials Express, 8, 824-835(2018).

[26] Notte M L. Passaro V M N. Ultra high sensitivity chemical photonic sensing by Mach-Zehnder interferometer enhanced Vernier-effect[J]. Sensors and Actuators B: Chemical, 176, 994-1007(2013).

[27] Dai D X. Highly sensitive digital optical sensor based on cascaded high-Q ring-resonators[J]. Optics Express, 17, 23817-23822(2009).

[28] Troia B, Penades J S, Khokhar A Z et al. Germanium-on-silicon Vernier-effect photonic microcavities for the mid-infrared[J]. Optics Letters, 41, 610-613(2016).

[29] Chana Y H, Ho C P, Dong B W et al. Development of mid-IR ring resonators using vernier effect[C]∥2018 International Conference on Optical MEMS and Nanophotonics (OMN). July 29-August 2, 2018, Lausanne, Switzerland., 1-2(2018).

[30] Raghunathan V, Shori R, Stafsudd O M et al. Nonlinear absorption in silicon and the prospects of mid-infrared silicon Raman lasers[J]. Physica Status Solidi (a), 203, R38-R40(2006).

[31] Liu M L, Wang L R, Sun Q B et al. Influences of multiphoton absorption and free-carrier effects on frequency-comb generation in normal dispersion silicon microresonators[J]. Photonics Research, 6, 238-243(2018). http://www.opticsjournal.net/Articles/Abstract?aid=OJ180330000165eKhNkQ

[32] Griffith A G, Yu M J, Okawachi Y et al. Coherent mid-infrared frequency combs in silicon-microresonators in the presence of Raman effects[J]. Optics Express, 24, 13044-13050(2016).

[33] Fan W C, Wang L R, Zhang W F et al. Low-threshold 4/5 octave-spanning mid-infrared frequency comb in a LiNbO3 microresonator[J]. IEEE Photonics Journal, 11, 1-7(2019).

[34] Guo Y, Wang J, Han Z et al. Power-efficient generation of two-octave mid-IR frequency combs in a germanium microresonator[J]. Nanophotonics, 7, 1461-1467(2018).

[35] Fei Y, He Y M, Yang F H et al. Effect of backreflection and normal mode loss on the transmission of waveguide ring resonator[J]. Chinese Journal of Lasers, 45, 0513001(2018).

[36] Mu Z, Liu C J, Wu X S et al. Feedback-coupled waveguide microring resonator based on slot structure[J]. Acta Optica Sinica, 39, 1213001(2019).

[37] Hu J, Sun X, Agarwal A et al. Design guidelines for optical resonator biochemical sensors[J], 26, 1032-1041(2009).

[38] Miller S A, Griffith A G, Yu M J et al. Low-loss air-clad suspended silicon platform for mid-infrared photonics[C]∥2016 Conference on Lasers and Electro-Optics (CLEO). June 5-10, 2016, San Jose, CA, USA., 1-2(2016).

[39] Chen Y, Lin H T, Hu J J et al. Heterogeneously integrated silicon photonics for the mid-infrared and spectroscopic sensing[J]. ACS Nano, 8, 6955-6961(2014).

[40] Hu J J. Ultra-sensitive chemical vapor detection using micro-cavity photothermal spectroscopy[J]. Optics Express, 18, 22174-22186(2010).

[41] Vigreux-Bercovici C, Bonhomme E, Pradel A et al. Transmission measurement at 10.6 μm of Te2As3Se5 rib waveguides on As2S3 substrate[J]. Applied Physics Letters, 90, 011110(2007).

[42] Xia X, Chen Q, Tsay C et al. Low-loss chalcogenide waveguides on lithium niobate for the mid-infrared[J]. Optics Letters, 35, 3228-3230(2010).

[43] Haas J, Artmann P, Mizaikoff B. Mid-infrared GaAs/AlGaAs micro-ring resonators characterized via thermal tuning[J]. RSC Advances, 9, 8594-8599(2019).

[44] Boeck R, Shi W, Chrostowski L et al. FSR-eliminated vernier racetrack resonators using grating-assisted couplers[J]. IEEE Photonics Journal, 5, 2202511(2013).

[45] Boeck R, Jaeger N A, Rouger N et al. Series-coupled silicon racetrack resonators and the Vernier effect: theory and measurement[J]. Optics Express, 18, 25151-25157(2010).

[46] Hoste J W, Soetaert P, Bienstman P. Improving the detection limit of conformational analysis by utilizing a dual polarization Vernier cascade[J]. Optics Express, 24, 67-81(2016).

[47] Notte M L, Troia B, Muciaccia T et al. Recent advances in gas and chemical detection by Vernier effect-based photonic sensors[J]. Sensors (Basel, Switzerland), 14, 4831-4855(2014).

[48] Ho C P, Zhao Z, Li Q et al. Mid-infrared tunable Vernier filter on a germanium-on-insulator photonic platform[J]. Optics Letters, 44, 2779-2782(2019).

[49] Troia B, Khokhar A Z, Nedeljkovic M et al. Design procedure and fabrication of reproducible silicon vernier devices for high-performance refractive index sensing[J]. Sensors (Basel, Switzerland), 15, 13548-13567(2015).

[50] Passaro V M N, de Tullio C, Troia B et al. Recent advances in integrated photonic sensors[J]. Sensors (Basel, Switzerland), 12, 15558-15598(2012).

[51] Passaro V M N, Troia B, De Leonardis F. A generalized approach for design of photonic gas sensors based on Vernier-effect in mid-IR[J]. Sensors and Actuators B: Chemical, 168, 402-420(2012).

[52] Troia B, Khokhar A Z, Nedeljkovic M et al. Cascade-coupled racetrack resonators based on the Vernier effect in the mid-infrared[J]. Optics Express, 22, 23990-24003(2014).

[53] Schliesser A, Picqué N, Hänsch T W. Mid-infrared frequency combs[J]. Nature Photonics, 6, 440-449(2012).

[54] Leindecker N, Marandi A, Byer R L et al. Broadband degenerate OPO for mid-infrared frequency comb generation[J]. Optics Express, 19, 6296-6302(2011).

[55] Vodopyanov K L, Sorokin E, Sorokina I T et al. Mid-IR frequency comb source spanning 4.4-5.4 μm based on subharmonic GaAs optical parametric oscillator[J]. Optics Letters, 36, 2275-2277(2011).

[56] Leindecker N, Marandi A, Byer R L et al. Octave-spanning ultrafast OPO with 2.6-6.1 μm instantaneous bandwidth pumped by femtosecond Tm-fiber laser[J]. Optics Express, 20, 7046-7053(2012).

[57] Adler F, Cossel K C, Thorpe M J et al. Phase-stabilized, 1.5 W frequency comb at 2.8-4.8 μm[J]. Optics Letters, 34, 1330-1332(2009).

[58] Jin Y W, Cristescu S M. Harren F J M, et al. Two-crystal mid-infrared optical parametric oscillator for absorption and dispersion dual-comb spectroscopy[J]. Optics Letters, 39, 3270-3273(2014).

[59] Keilmann F, Amarie S. Mid-infrared frequency comb spanning an octave based on an Er fiber laser and difference-frequency generation[J]. Journal of Infrared, Millimeter, and Terahertz Waves, 33, 479-484(2012).

[60] Cruz F C, Maser D L, Johnson T et al. Mid-infrared optical frequency combs based on difference frequency generation for molecular spectroscopy[J]. Optics Express, 23, 26814-26824(2015).

[61] Ruehl A, Gambetta A, Hartl I et al. Widely-tunable mid-infrared frequency comb source based on difference frequency generation[J]. Optics Letters, 37, 2232-2234(2012).

[62] Hugi A, Villares G, Blaser S et al. Mid-infrared frequency comb based on a quantum cascade laser[J]. Nature, 492, 229-233(2012).

[63] Vasilyev S, Mirov M, Gapontsev V. Kerr-lens mode-locked femtosecond polycrystalline Cr 2+: ZnS and Cr 2+: ZnSe lasers[J]. Optics Express, 22, 5118-5123(2014).

[64] Sorokin E, Sorokina I T, Mandon J et al. Sensitive multiplex spectroscopy in the molecular fingerprint 2.4 μm region with a Cr 2+∶ZnSe femtosecond laser[J]. Optics Express, 15, 16540-16545(2007).

[65] Luke K, Okawachi Y. Lamont M R E, et al. Broadband mid-infrared frequency comb generation in a Si3N4 microresonator[J]. Optics Letters, 40, 4823-4826(2015).

[66] He M F, Chen K X, Hu Z F. Kerr optical frequency comb based on micro-ring resonator with thermal effect[J]. Laser & Optoelectronics Progress, 55, 091901(2018).

[67] Wang C Y, Herr T. Del'Haye P, et al. Mid-infrared optical frequency combs at 2.5 μm based on crystalline microresonators[J]. Nature Communications, 4, 1345(2013).

[68] Yu M J, Okawachi Y, Griffith A G et al. Mode-locked mid-infrared frequency combs in a silicon microresonator[J]. Optica, 3, 854-860(2016).

[69] Del'Haye P, Schliesser A, Arcizet O et al. Optical frequency comb generation from a monolithic microresonator[J]. Nature, 450, 1214-1217(2007).

[70] Zhang L, Agarwal A M, Kimerling L C et al. Nonlinear Group IV photonics based on silicon and germanium: from near-infrared to mid-infrared[J]. Nanophotonics, 3, 247-268(2014).

[71] Chembo Y K, Menyuk C R. Spatiotemporal Lugiato-Lefever formalism for Kerr-comb generation in whispering-gallery-mode resonators[J]. Physical Review A, 87, 053852(2013).

[72] Kippenberg T J, Spillane S M, Vahala K J. Kerr-nonlinearity optical parametric oscillation in an ultrahigh-Q toroid microcavity[J]. Physical Review Letters, 93, 083904(2004).

[73] Wang Y W, Zhang M M, Xia L et al. Progress in dispersion control of micro-ring resonator-based optical frequency comb generation[J]. Laser & Optoelectronics Progress, 51, 060001(2014).

[74] Coen S, Erkintalo M. Universal scaling laws of Kerr frequency combs[J]. Optics Letters, 38, 1790-1792(2013).