[1] Tonouchi M. Cutting-edge terahertz technology[J]. Nature Photonics, 1, 97-105(2007).

[2] Köhler R, Tredicucci A, Beltram F et al. Terahertz semiconductor-heterostructure laser[J]. Nature, 417, 156-159(2002).

[3] Williams B S. Terahertz quantum-cascade lasers[J]. Nature Photonics, 1, 517-525(2007).

[4] Kazarinov R F, Henry C H. Second-order distributed feedback lasers with mode selection provided by first-order radiation losses[J]. IEEE Journal of Quantum Electronics, 21, 144-150(1985). http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1072627

[5] Shams-Zadeh-Amiri A M, Hong J, Li X et al. . Second- and higher order resonant gratings with gain or loss-Part I: Green’s function analysis[J]. IEEE Journal of Quantum Electronics, 36, 1421-1430(2000). http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=892562

[6] Shams-Zadeh-Amiri A M, Hong J, Li X et al. . Second- and higher order resonant gratings with gain or loss-Part II: Designing complex-coupled DFB lasers with second-order gratings[J]. IEEE Journal of Quantum Electronics, 36, 1431-1437(2000). http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=892563

[7] Glinski J, Makino T. Yield analysis of second-order DSM DFB lasers and implications for design[J]. IEEE Journal of Quantum Electronics, 23, 849-859(1987). http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1073441

[8] Ye S J, Qin L, Qi X D et al. Emission characteristics of second-order distributed feedback semiconductor lasers[J]. Chinese Journal of Lasers, 37, 2371-2375(2010).

[9] Schultz C M, Crump P, Wenzel H et al. Narrow vertical far-field 975-nm broad-area DFB lasers for wide temperature range operation[J]. IEEE Photonics Technology Letters, 21, 593-595(2009). http://ieeexplore.ieee.org/document/4783066/

[10] Shi J X, Qin L, Ye S J et al. A 927 nm distributed feedback laser with surface second-order metal grating[J]. Journal of Optoelectronics·Laser, 22, 1488-1491(2011).

[11] Wang Q, Guo J J, Chen W et al. Widely tunable distributed feedback semiconductor lasers with constant power and narrow linewidth[J]. Chinese Journal of Lasers, 44, 0101004(2017).

[12] Mahler L, Köhler R, Tredicucci A et al. Single-mode operation of terahertz quantum cascade lasers with distributed feedback resonators[J]. Applied Physics Letters, 84, 5446-5448(2004). http://scitation.aip.org/content/aip/journal/apl/84/26/10.1063/1.1767957

[13] Demichel O, Mahler L, Losco T et al. Surface plasmon photonic structures in terahertz quantum cascade lasers[J]. Optics Express, 14, 5335-5345(2006). http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-12-5335

[14] Kumar S, Williams B S, Qin Q et al. Surface-emitting distributed feedback terahertz quantum-cascade lasers in metal-metal waveguides[J]. Optics Express, 15, 113-128(2007). http://www.ncbi.nlm.nih.gov/pubmed/19532227

[15] Wang T, Liu J Q, Liu F Q et al. Tri-channel single-mode terahertz quantum cascade laser[J]. Optics Letters, 39, 6612-6615(2014). http://www.opticsinfobase.org/ol/upcoming_pdf.cfm?id=222738

[16] Li Y, Wang J, Yang N et al. The output power and beam divergence behaviors of tapered terahertz quantum cascade lasers[J]. Optics Express, 21, 15998-16006(2013). http://www.ncbi.nlm.nih.gov/pubmed/23842386

[17] Pan Z C[M]. A course in method of mathematical physics, 591-596(1993).

[18] Wang J, Wu W D, Zhang X L et al. Analysis of terahertz quantum cascade laser beam[J]. Chinese Journal of Computational Physics, 29, 127-132(2012).

[19] Bai Y F, Fan J, Zou Y G et al. Fabrication of gratings used in 976 nm distributed feedback lasers based on laser interference lithography[J]. Laser & Optoelectronics Progress, 54, 120501(2017).