33 W continuous-wave single-frequency green laser by frequency doubling of a single-mode YDFA

Abstract

A high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier (YDFA) is developed. A linearly polarized single-mode fiber amplifier produces a 60 W infrared laser at 1064 nm with a 103 W incident diode pump laser at 976 nm, corresponding to an optical conversion efficiency of 58%. An external bow-tie enhancement cavity incorporating a noncritically phase-matched lithium triborate crystal is employed for second-harmonic generation. A 33.2 W laser at 532 nm is obtained with a 45 W incident 1064 nm fundamental laser, corresponding to a conversion efficiency of 74%.OCIS Continuous-wave (CW) green lasers have many scientific and industrial applications, including laser display [1,2] , pumping of Ti-sapphire and dye lasers [3] , semiconductor mask inspection [4] , the generation of CW UV radiation by second-harmonic generation (SHG) [5] , etc. Due to the lack of solid state gain medium that can directly lase at the green spectral range, the standard method for generating a green laser is nonlinear frequency conversion. Periodically poled lithium niobate/tantalite (LiNbO 3 ∕LiTaO 3 ) or potassium titanyl phosphate (KTP) can be used to efficiently produce visible sources by a single-pass SHG of near-infrared lasers, which have a high effective nonlinear coefficient d eff . But, they are prone to damage when the incident fundamental power is higher than multiple tens of watts [6][7][8][9] . For high power applications, the use of nonlinear crystals with a higher tolerance to optical power is necessary. Lithium triborate (LBO) is an excellent nonlinear crystal with a high damage threshold, which, however, has a smaller d eff . Intracavity frequency doubling is commonly used in solid state lasers to improve the SHG efficiency by increasing the fundamental power incident on the nonlinear crystal. However, the thermal effects in the laser medium limit the output power and the optical beam quality [10,11]

10 W low-noise green laser generation by the single-pass frequency doubling of a single-frequency fiber amplifier

“…Several technologies are striving to achieve these goals. The second-harmonic generation (SHG) of diode-pumped solid-state lasers [8], optically pumped semiconductor lasers [9], and fiber lasers [10] can produce a high-power green laser output. Compared to the other technologies, fiber lasers are compact, cost-effective, and have excellent power scalability.…”

High efficiency frequency doubling with a passive enhancement cavity

“…The active control can work well with a proper design. Nevertheless, it adds complexity to the laser systems [13][14][15].…”