Passively Q-switched 8.5-ns Pr3+:YLF laser at 640 nm

Abstract

We report on short pulse generation from a passively Q-switched Pr3+:LiYF4 laser operating at 640 nm. By reducing the cavity length and utilizing Co:MgAl2O4 as the saturable absorber, we obtain the shortest pulse durations from any Q-switched Pr3+ laser. Under pumping with a frequency-doubled optically pumped semiconductor laser at a wavelength of 479.05 nm we realized (8.5 ± 1) ns long pulses at a repetition rate of 0.78 MHz from a 7.5 mm long cavity at an average output power of 1.0 W. In that case, the laser pulse energy and duration were 1.3 µJ and 8.5 ns, respectively. The highest pulse energy amounts to 1.8 µJ at a pulse peak power of 0.19 kW in 9.2 ns pulses at a repetition rate of 0.48 MHz.

Few-ns, kW peak power Q-switched pulses from orange and red Pr:YLF lasers

“…Compared to the first report utilizing a V-shaped longer resonator, 11) we reduced the pulse duration and increased the peak power for the 640 and 607 nm lasers by orders of magnitude and for the 523 nm operation the pulse duration was decreased by a factor of two. Compared to our recent work with a similar compact resonator configuration, 13) we further reduced the pulse duration by a factor of more than three and increased the peak power by more than a factor of five at 640 nm. Compared to the report of 20 W-direct diode pumping with a longer V-shaped resonator, 12) our miniaturized resonator reached an order of magnitude shorter pulses, and thus comparable (640 nm) or even higher (607 nm) peak power levels.…”

“…Various materials have been investigated as saturable absorbers (SAs) for Pr 3+ -based lasers. 9,10) Among these, we previously demonstrated the Co 2+ -doped spinel crystal (Co 2+ :MgAl 2 O 4 ) to be an outstanding SA for passively Q-switched visible Pr 3+ :LiYF 4 (Pr:YLF) lasers, [11][12][13] yielding a simple approach for pulsed visible and UV sources demanded for materials processing, 14) lithography, 15) and wafer inspection. 16) UV lasers enable non-thermal processing by direct chemical bond breaking in the processed materials.…”

“…12) More recently, we achieved the first sub 10 ns pulses at 1 W of average power at 0.78 MHz repetition rate and a peak power of 0.14 kW. 13) Here, we investigate the influence of the SA parameters on the Q-switching performance of Pr:YLF lasers operated in the visible in order to achieve even higher peak powers. We obtained 1.1 kW of peak power in pulses as short as 2.4 ns at 640 nm, while at 607 nm in the orange we obtain a peak power as high as 1.2 kW in 5.3 ns pulses under pumping with only 5 W from a frequency-doubled optically-pumped semiconductor laser (2ω-OPSL).…”

“…The resonator shorter than 1 cm reduced the resonator round trip time and thus pulse duration in all experiments. Compared to previous work, 13) we minimized any air spacing between optical elements, maintaining only the necessary room for independent alignment of each component. We used a 5 mm long and 5 mm diameter a-cut cylindrical Pr 3+ (0.6 at%):YLF crystal (Optogama UAB).…”

Blue LD-pumped electro-optically Q-switched Pr:YLF visible laser with kilowatt-level peak power

“…Recently, Kränkel et al report a passively Q-switched Pr:YLF laser at 640 nm by used Co:MALO as an SA. In their work, the pulse energy of 1.3 μJ and the pulse width of 8.5 ns were realized from a 7.5 mm long cavity [15]. However, the passively Q-switched technique has a disadvantage in the uncontrolled pulse repetition rates and poor pulse instabilities.…”