Amplification and frequency quadrupling of picosecond long duration burst-mode laser

• Flat-top macro-pulse envelope is obtained by accurately delaying time between front edges of macro-pulses and pump pulses. • To improve nonlinear conversion efficiency and beam quality of 266 nm laser, elliptically focused 532 nm spot is shaped. By employing two laser diodes (LDs) dual-end pulse-pumped a Nd:YVO 4 crystal amplification, LiB 3 O 5 (LBO) crystal frequency doubling and β-BaB 2 O 4 (BBO) crystal frequency quadrupling, a 266 nm picosecond burst-mode laser is observed. The macro-pulse width of 16 μs and the macro-pulse repetition rate of 550 Hz are realized by using the electro-optic modulator (EOM) to pick up micro-pulses output from a 1064 nm laser source with pulse width of 18 ps and frequency repetition of 178 MHz. By actually delaying the time between front edges of macro-pulses and pump pulses, flat-top amplified macro-pulse envelope is obtained. The amplified macro-pulse has the micro-pulse energy of 787 nJ at the optimal delay time of 49.5 μs, corresponding beam quality of M x 2 = 1.30, M y 2 =1.29. The frequency doubling burst-mode laser is obtained with the micro-pulse energy of 531 nJ, corresponding to beam quality of M x 2 = 1.15, M y 2 =1.18. The conversion efficiency from 1064 nm to 532 nm is 67%. Elliptically focused 532 nm beam is used to match the narrow longitudinal acceptance angle of type-Ⅰ BBO crystal. The 266 nm micro-pulses have the pulse energy of 135 nJ. The conversion efficiency from 532 nm to 266 nm is 25%, and the total conversion efficiency from 1064 nm to 266 nm is 17%. The beam quality of the 266 nm burst-mode laser is M x 2 = 1.15 and M y 2 = 1.25.