Compact deep ultraviolet frequency-doubled Tb:LiYF4 lasers at 272 nm

A new laser system has been developed to generate coherent deep ultraviolet (DUV) radiation at 272 nm. The DUV lasers were produced via intra-cavity frequency doubling of the T b 3 + : L i Y F 4 lasers emitting fundamentally at 544 nm. Continuous-wave (cw) and Q -switched operations were performed with a type I phase-matched β − B a B 2 O 4 nonlinear crystal. The cw operation produces 127 mW of averaged DUV output power. Passive Q -switched operation was realized by using C o 2 + : M g A l 2 O 4 saturable absorbers. At an initial transmittance (excluding Fresnel reflections) of 99% at 544 nm, stable pulsed output at 272 nm with maximum single-pulse energy of 7.6 µJ and peak power of 6.1 W was obtained. Furthermore, by employing a smaller initial transmittance of 94.7%, we achieved maximum averaged DUV output power of 277 mW. The statistically averaged single-pulse DUV energy and peak power were estimated to be around 100 µJ and 320 W, respectively, which indicates great potential for this DUV laser system toward high energy and peak power.