在醫療、工業、通訊、國防、環境等各種領域上，波長位於2微米到5微米的中紅外波段雷射扮演著重要的角色，眾多系統皆以此做為光源基礎才得以建立。本研究為基於腔內光參振盪的技術，結合雷射與非線性系統的共振腔，開發出可連續調變波長之中紅外雷射光源。研究內容主要分為四個部份：
第一部分為開發出具有小型、低啟動閾值特性之中紅外光雷射，此雷射在120mW的808奈米雷射二極體下即可被驅動，在540mW的輸入下可在3470奈米輸出39mW，整體體積僅有852421.5 mm3，可手持及透過電池驅動。第二部份為在第一部份的基礎上，將輸出能量提升到230mW，並實現了2700~3600奈米的波長調變輸出，其調整範圍大於900奈米。第三部份進一步的架設出具有單縱模輸出特性的中紅外雷射，並達成了>20GHz的波長連續調變範圍，此調變與頻率特性為在腔內光參振盪結構下的首次達成。
最後一部份為將中紅外光雷射與光聲光譜系統結合，進行了相關的氣體檢測應用實驗，實驗內容包含了低濃度如CH4、HCL、CO等氣體的檢測、CH4及其同位素的量測與分辨，確定了開發的雷射系統在應用層面上的適用性與其價值。

Coherent mid-infrared (MIR) laser sources, typically ranging from 2m to 5m, is an attractive research topic due to its variety of application need, such as breath analysis, industry process control, clinic treatment, free space communications, military purpose and the environmental biogas detection. As a result, there's a growing demand to have the mid-infrared laser source compact, low cost and easy handling. Furthermore, for some special request, such as the precision spectroscopy, the MIR laser even needs to be operated in the single longitudinal mode with the capability of the mode-hop free tuning.
In this thesis, we proposed and experimentally demonstrated a MIR laser system which contains the features of compact and low threshold based on the intracavity singly resonant optical parametric oscillation (ICSRO) technique. The system can be pumped by a 120mW 808nm laser diode and is small enough to be handheld. We have also extend this ICSRO structure to achieve >900nm tuning range in MIR under single longitudinal mode operation, and >20GHz mode-hop free tuning has been demonstrated under the synchronization of the etalon incident angle and the cavity length. Finally, a photoacoustic spectroscopy system has been built to demonstrate the application use for our MIR laser source, several gas in the sub ppm level concentration has been successfully detected, and CH4 isotope which the absorption spectrum has narrow linewidth with large peak spacing has also been clearly detected by the mode-hop free tuning function of our MIR laser.

Chapter 1 Introduction 1
Chapter 2 CW MIR Lser 6
2.1 Quantum cascade laser diode 6
2.2 Solid state laser 8
2.3 Nonlinear wavelength converters 12
Chapter 3 Theory of ICSRO 20
3.1 Laser oscillation 20
3.2 Singly resonant OPO 27
3.3 Intracavity singly resonant OPO 33
3.4 Single longitudinal mode operation 37
3.5 Mode-hop free tuning 39
Chapter 4 Design of ICSRO system 41
4.1 Cavity structure and the mode matching 41
4.2 Structure of the periodical poled lithium niobate 43
4.3 Achievement of the single longitudinal mode operation 46
4.4 Wavelength tuning mechanisms 50
Chapter 5 Experiment result of ICSROs 55
5.1 Compact and low threshold 55
5.2 Broadband and wide tuning 58
5.3 Single longitudinal mode operation 60
5.4 Mode-hop free tuning 61
Chapter 6 Application to gas sensing 65
6.1 Photoacoustic spectroscopy 65
6.2 Low concentration measurement 67
6.3 CH4 isotope measurement 69
Chapter 7 Conclusion and future perspective 72
Reference 74

[1] C. Wang and P. Sahay, "Breath analysis using laser spectroscopic techniques: breath biomarkers, spectral fingerprints, and detection limits," Sensors 9, 8230-8262 (2009).

[2] S. Schilt, L. Thevenaz, M. Niklès, L. Emmenegger, C. Hüglin, " Ammonia monitoring at trace level using photoacoustic spectroscopy," Spectrochim, Acta A 60, 3259-3268 (2004).

[3] R. Hibst, U. Keller, "Experimental studies of the application of the Er:YAG laser on dental hard substances, I. Measurements of the ablation rate," Lasers Surg Med 9, 338-344 (1989).

[4] D. M. Bubb, J. S. Horwitz, R. A. McGill, D. B. Chrisey, M. R. Papantonakis, R. F. Haglund, Jr., and B. Toftmann, “Resonant infrared pulsed-laser deposition of a sorbent chemoselective polymer,” Appl. Phys. Lett. 79, 2847-2849 (2001).

[5] R. Martini and E. A. Whittaker, “Quantum cascade laser-based free space optical communications,” J. Opt. Fiber. Commun. Rep. 2, 279-292 (2005).

[6] A. Sijan, “Development of military lasers for optical countermeasures in the Mid-IR,” Proc. SPIE 7483, 748304 (2009).

[7] T. Harashima, J. Kinoshita, Y. Kimura, A. Brugnera, F. Zanin, J. D. Peccora, K. Matsumoto, "Morphological comparative study on ablation of dental hard tissues at cavity preparation by Er:YAG and Er,Cr:YSGG lasers," Photomed Laser Surg. 23, 52-55 (2005)

[8] T. Popmintchev, M. C. Chen, D. Popmintchev, P. Arpin, S. Brown, S. Alisauskas, G. Andriukaitis, T. Balciunas, O. D. Mucke, A. Pugzlys, A. Baltuska, B. Shim, S. E. Schrauth, A. Gaeta, C. Hernandez-Garcia, L. Plaja, A. Becker, A. Jaron-Becker, M. M. Murnane, and H. C. Kapteyn," Bright Coherent Ultrahigh Harmonics in the keV X-ray Regime from Mid-Infrared Femtosecond Lasers," Science 336, 1287 (2012).


[9] F. K. Tittel, D. Richter, and A. Fried, “Mid-infrared laser applications in spectroscopy” in Solid-State Mid-Infrared Laser Sources, Topics in Appl. Phys. 89, I. T. Sorokina, K. L. Vodopyanov (eds) (Spinger-Verlag, Berlin, 2003), pp. 445-516

[10] L. Dong, Y. Yu, C. Li, S. So, and F. K. Tittel, “Ppb-level formaldehyde detection using a CW room-temperature interband cascade laser and a miniature dense pattern multipass gas cell,” Opt. Express 23, 19821–19830 (2015).

[11] J. Nwaboh, S. Persijn, K. Heinrich, M. Sowa, and O. Werhahn, "QCLAS and CRDS based CO quantification as aimed at in breath measurements," Int. J. Spectros., 2012, 894841 (2012).

[12] W. Ye, C. Zheng, F. K. Tittel, N. P. Sanchez, A. K. Gluszek, A. J. Hudzikowski, M. Lou, L. Dong, R. J. Griffin, "A compact mid-infrared dual-gas CH4/C2H6 sensor using a single interband cascade laser and custom electronics,’’ Proc. SPIE 10111, Quantum Sensing and Nano Electronics and Photonics XIV, 1011134, January 27, (2017)

[13] H. Waechter and M. W. Sigrist, “Mid-infrared laser spectroscopic determination of isotope ratios of N2O at trace levels using wavelength modulation and balanced path length detection,” Appl. Phys. B 87, 539-546 (2007).

[14] C. Gmachl, F. Capasso, D. L. Sivco, and Q. Y. Cho, “Recent progress in quantum cascade lasers and applications,” Rep. Prog. Phys. 64, 1533-1601 (2001).

[15] A. Sennaroglu, U. Demirbas, N. Vermeulen, H. Ottevaere, and H. Thienpont, “Continuous-wave broadly tunable Cr2+:ZnSe laser pumped by a thulium fiber laser,” Opt. Commun. 268, 115-120 (2006).

[16] D. Richter, A. Fried, B. Wert, J. G. Walega, and F. K. Tittel, “Development of a tunable mid-IR difference frequency laser source for highly sensitive airborne trace gas detection,” Appl. Phys. B. 75, 281-288 (2002).

[17] L. E. Myers, G. D. Miller, R. C. Eckardt, M. M. Fejer, and R. L. Byer, “Quasi-phase-matched 1.064 micron-pumped optical parametric oscillator in bulk periodically poled LiNbO3”, Opt. Lett. 20, 52-54 (1995).

[18] M. Ebrahimzadeh, G. A. Turnbull, T. J. Edwards, D. J. M. Stothard, I. D. Lindsday, M. H. Dunn, "Intracavity continuous-wave singly resonant optical parametric oscillators," J. Opt. Soc. Am. B 16, 1499-1511 (1999).

[19] J. Y. Lai, C. W. Hsu, E. C. Liu, Y. C. Chen, D. Y. Wu, M. H. Chou, and S. D. Yang, “A 3.5 μm continuous wave laser pointer,” Conference on Lasers & Electro Optics, San Jose, California, USA, June 5-10, 2016.

[20] J. Y. Lai, H. T. Guo, Y. C. Chen, C. W. Hsu, D. Y. Wu, M. H. Chou, and S. D. Yang, "Single-frequency Mod-hop Free Tunable 3μm Laser Pumped by a 2W Diode for Isotopic Gas Sensing," Conference on Lasers & Electro Optics, San Jose, California, USA, May 13-18, 2018.

[21] R. F. Kazarinov and R. A. Suris, “Possibility of the amplification of electromagnetic waves in a semiconductor with a superlattice,” Sov. Phys. Semicond. 5, 707–709 (1971).

[22] J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, A. Y. Cho, Quantum cascade laser, Science 264, 553-556 (1994).

[23] P. Figueiredo, M. Suttinger, R. Go, E. Tsvid, C. K. N. Patel, and A. Lyakh, “Progress in high-power continuous wave quantum cascade lasers,” Appl. Opt. 56, H15-H23 (2017).

[24] M. S. Vitiello, G. Scalari, B. Williams, and P. De Natale, " Quantum cascade lasers: 20 years of challenges," Opt. Express 23, 5167 (2015).

[25] M. Razeghi, W. Zhou, S. Slivken, Q. Y. Lu, D. Wu, and R. McClintock, “Recent progress of quantum cascade laser research from 3 to 12 μm at the Center for Quantum Devices,” Appl. Opt. 56, H30–H44 (2017).

[26] J. M. Wolf, S. Riedi, M. J. Süess, M. Beck, and J. Faist, "3.36 µm single-mode quantum cascade laser with a dissipation below 250 mW," Opt. Express 24, 662-671 (2016)

[27] J. Faist, C. Gmachl, F. Capasso, C. Sirtori, D. L. Sivco, J. N. Baillargeon, and A. Y. Cho “Distributed feedback quantum cascade lasers,” Appl. Phys. Lett. 70, 2670-2672 (1997).

[28] R. Maulini, M. Beck, J. Faist, and E. Gini, “Broadband tuning of external cavity bound-to-continuum quantum cascade lasers,” Appl. Phys. Lett. 84, 1659 (2004).

[29] R. Centeno, D. Marchenko, J. Mandon, S. M. Cristescu, G. Wulterkens, and F. J. M. Harren, “High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection,” Appl. Phys. Lett. 105, 261907 (2014).

[30] G. Wysocki, R. F. Curl, F. K. Tittel, R. Maulini, J. M. Bulliard, and J. Faist, “Widely tunable mode-hop free external cavity quantum cascade laser for high resolution spectroscopic applications,” Appl. Phys. B 81, 769-777 (2005).

[31] L. D. DeLoach, R. H. Page, G. D. Wilke, S. A. Payne, and W. F. Krupke, “Transition metal-doped zinc chalcogenides: Spectroscopy and laser demonstration of a new class of gain media,” IEEE J. Quantum Electron 32, 885-895 (1996).

[32] S. Mirov, V. Fedorov, D. Martyshkin, I. Moskalev, M. Mirov, and S. Vasilyev, “Progress in mid-IR lasers based on Cr and Fe doped II-VI chalcogenides,” IEEE J. Sel. Top. Quantum Electron. 21, 1601719 (2015).

[33] E. Sorokin, I. T. Sorokina, M. S. Mirov, V. V. Fedorov, I. S. Moskalev, and S. B. Mirov, “Ultrabroad continuous-wave tuning of ceramic Cr:ZnSe and Cr:ZnS lasers,” Advanced Solid State Photonics, San Diego, CA, USA 2010, San Diego, USA, January 31- February 3 (2010).

[34] S. Vasilyev, I. Moskalev, M. Mirov, V. Smolski, S. Mirov, and V. Gapontsev, “Recent breakthroughs in solidstate mid-IR laser technology,” Laser Tech. J., 13, 1-5 (2016).

[35] P. Canarelli, Z. Benko, R. F. Curl, and F. K. Tittel, “Continuous-wave infrared laser spectrometer based on difference frequency generation in AgGaS2 for high-resolution spectroscopy,” J. Opt. Soc. Am. B 9, 197-202 (1992).

[36] S. Guha, J. O. Barnes, and L. P. Gonzalez, " Multiwatt-level continuous-wave midwave infrared generation using difference frequency mixing in periodically poled MgO-doped lithium niobate,", Opt. Lett. 39, 5018 (2014).

[37] U. Bader, T. Mattern, T. Bauer, J. Bartschke, M. Rahm, A. Borsutzky, and R. Wallenstein, "Pulsed nanosecond optical parametric generator based on periodically poled lithium niobate," Opt. Commun. 217, 375-380 (2003).

[38] L. E. Myers, R. C. Eckardt, M. M. Fejer, R. L. Byer, and W. R. Bosenberg, " Multigrating quasi-phase-matched optical parametric oscillator in periodically poled LiNbO3," Opt. Lett. 21, 591 (1996).

[39] F. G. Colville, M. J. Padgett, and M. H. Dunn, " Continuous‐wave, dual‐cavity, doubly resonant, optical parametric oscillator," Appl. Phys. Lett. 64, 1490 (1994).

[40] R. Al-Tahtamouni, K. Bencheikh, R. Storz, K. Schneider, M. Lang, J. Mlynek, and S. Schiller, “Long-term stable operation and absolute frequency stabilization of a doubly resonant parametric oscillator,” Appl. Phys. B 66, 733-39 (1998).

[41] J. U. F¨urst, D. V. Strekalov, D. Elser, M. Lassen, U. L. Andersen, C. Marquardt, and G. Leuchs, " Low-threshold Optical Parametric Oscillations in a Whispering Gallery Mode Resonator," Phys. Rev. Lett. 104, 153901 (2010).

[42] G. A. Turnbull, D. McGloin, I. D. Lindsay, M. Ebrahimzadeh, M. H. Dunn: Extended mode-hop-free tuning using a dual-cavity, pump-enhanced optical parametric oscillator," Opt. Lett. 25, 341–343 (2000).

[43] M. Ebrahimzadeh, G. A. Turnbull, T. J. Edwards, D. J. M. Stothard, I. D. Lindsday, M. H. Dunn, "Intracavity continuous-wave singly resonant optical parametric oscillators," J. Opt. Soc. Am. B 16, 1499-1511 (1999).

[44] W. K. Chang, Y. H. Chen, H. H. Chang, J. W. Chang, C. Y. Chen, Y. Y. Lin, Y. C. Huang, and S. T. Lin, "Two-dimensional PPLN for simultaneous laser Q-switching and optical parametric oscillation in a Nd:YVO4 laser," Opt. Express 19, 23643-23651 (2011).

[45] T. H. Maiman, “Stimulated optical radiation in ruby,” Nature 187, 493 (1960).

[46] J. J. Zayhowski, “The effects of spatial hole burning and energy diffusion on the single-mode operation of standing-wave lasers,” IEEE J. Quantum Electron. 26, 2052-2057 (1990).

[47] M. Vainio, J. Peltola, S. Persijn, F. J. M. Harren, and L. Halonen, " Singly resonant cw OPO with simple wavelength tuning," Opt. Express 16, 11141 (2008).

[48] O. Gayer, Z. Sacks, E. Galun, and A. Arie, "Temperature and wavelength dependent refractive index equations for MgO-doped congruent and stoichiometric LiNbO3," Appl. Phys. B 91, 343 (2008).

[49] J. Breguet,J. P. Pellaux, and N. Gisin, "Photoacoustic detection of trace gases with an optical microphone," Sensors Actuators A 1, 29-35 (1995).

[50] A.A. Kosterev, F.K. Tittel, D. Serebryakov, A.L. Malinovsky, I. Morozov, " Applications of Quartz Tuning Forks in Spectroscopic Gas Sensing," Rev. Sci. Instrum. 76, 1 (2005).

[51] V. Koskinen, J. Fonsen, K. Roth, J. Kauppinen, " Cantilever enhanced photoacoustic detection of carbon dioxide using a tunable diode laser source," Appl. Phys. B 86, 451 (2007).