[1] [1] Xu Xiafei, Lu Yanhua, Zhang Lei, et al. Technical study of 8.7 W continuous wave single frequency green laser based on extra-cavity frequency doubling［J］. Chinese J Lasers, 2016, 43(11): 1101010.

[2] [2] Yang Jianming, Tan Huiming, Tian Yubing, et al. All-solid-state doubly resonant intracavity sum-frequency 578 nm yellow laser with KTP type Ⅱ phase matching［J］. Chinese J Lasers, 2016, 43(10): 1001010.

[3] [3] Liu H, Hu J, Liu K, et al. High power room temperature 1014.8 nm Yb fiber amplifier and frequency quadrupling to 253.7 nm for laser cooling of mercury atoms［J］. Optics Express, 2013, 21(25): 30958-30963.

[4] [4] Scheid M, Markert F, Walz J, et al. 750 mW continuous-wave solid-state deep ultraviolet laser source at the 253.7 nm transition in mercury［J］. Optics Letters, 2007, 32(8): 955-957.

[5] [5] Fujii T, Kumagai H, Midorikawa K, et al. Development of a high-power deep-ultraviolet continuous-wave coherent light source for laser cooling of silicon atoms［J］. Optics Letters, 2000, 25(19): 1457-1459.

[6] [6] Porsev S G, Derevianko A. Hyperfine quenching of the metastable 3P0,2 states in divalent atoms［J］. Physical Review A, 2004, 69(4): 042506.

[7] [7] Almog G, Scholz M, Weber W, et al. A simplified scheme for generating narrow-band mid-ultraviolet laser radiation［J］. Review Scientific Instruments, 2015, 86(3): 033110.

[8] [8] Paul J, Kaneda Y, Wang T L, et al. Doppler-free spectroscopy of mercury at 253.7 nm using a high-power, frequency-quadrupled, optically pumped external-cavity semiconductor laser［J］. Optics Letters, 2011, 36(1): 61-63.

[9] [9] Steinborn R, Koglbauer A, Bachor P, et al. A continuous wave 10 W cryogenic fiber amplifier at 1015 nm and frequency quadrupling to 254 nm［J］. Optics Express, 2013, 21(19): 22693-22698.

[10] [10] Petersen M, Chicireanu R, Dawkins S T, et al. Doppler-free spectroscopy of the 1S0-3P0 optical clock transition in laser-cooled fermionic isotopes of neutral mercury［J］. Physical Review Letters, 2008, 101(18): 183004.

[11] [11] Hachisu H, Miyagishi K, Porsev S G, et al. Trapping of neutral mercury atoms and prospects for optical lattice clocks［J］. Physical Review Letters, 2008, 100(5): 053001.

[12] [12] Hansch T W, Couillaud B. Laser frequency stabilization by polarization spectroscopy of a reflecting reference cavity［J］. Optics Communications, 1980, 35(3): 441-444.

[13] [13] Boyd G D, Kleinman D A. Parametric interaction of focused Gaussian light beams［J］. Journal of Applied PhysIcs, 1968, 39(8): 3597-3639.

[14] [14] Vainio M, Bernard J E, Marmet L. Cavity-enhanced optical frequency doubler based on transmission-mode Hnsch-Couillaud locking［J］. Applied Physics B, 2011, 104(4): 897-908.

[15] [15] Polzik E S, Kimble H J. Frequency doubling with KNbO3 in an external cavity［J］. Optics Letters, 1991, 16(18): 1400-1402.

[16] [16] Kozlovsky W J, Nabors C D, Byer R L. Efficient second harmonic generation of a diode-laser-pumped CW Nd∶YAG laser using monolithic MgO∶LiNbO3 external resonant cavities［J］. IEEE Journal of Quantum Electronics, 1988, 24(6): 913-919.

[17] [17] Freegarde T, Zimmermann C. On the design of enhancement cavities for second harmonic generation［J］. Optics Communications, 2001, 199(5/6): 435-446.

[18] [18] Dong Tingting. Experimental research of the fourth harmonic 265.6 nm CW lasers［D］. Shanghai: East China Normal University, 2013.