7 March 2019 12-ps megawatt peak power pulses out of a single laser oscillator with nonlinear pulse compression
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Abstract
We present a passively Q-switched Nd3+:YAG/Cr4+:YAG laser with subsequent nonlinear pulse compression. This miniature laser combines both the high pulse energy of several tens of micro Joules and the short pulse duration of <20 ps without any amplification. It is therefore readily usable for many ultrafast applications including micro machining and medical applications. With these parameters, the laser shows a new level of compactness in comparison to other sub-100 picosecond laser sources. We utilize a Nd3+:YAG and a Cr4+:YAG crystal in a flat-Brewster, Brewsterflat configuration, respectively, positioned closely and the Brewster faces adjacent to each other. Pumped with approx. 6W from a fiber-coupled, 808 nm laser diode, the miniature, passively Q-switched laser oscillator delivers a pulse energy of 54 μJ with a pulse width of 339 ps and a repetition rate of 8.5 kHz. These pulses are subsequently coupled into a 20 μm core dia. large mode area PM fiber. Following a fiber propagation of 1.65 m the pulses are spectrally broadened by about a factor 40 due to self-phase modulation. Thereafter the nearly linearly chirped laser pulses are compressed by a chirped volume Bragg grating (CVBG). The optimized laser output pulses have a pulse width of 11.8 ps and a pulse energy of 20 μJ. We measured the polarized (PER<20dB) beam quality to be close to the diffraction limit with an M2≈1.5. A 13 hours continuous, stable laser operation has indicated a good long term stability and reliability.
Conference Presentation
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Hagen Kohl, Gabor Kulcsar, Daniel Kopf, and Bernd Braun "12-ps megawatt peak power pulses out of a single laser oscillator with nonlinear pulse compression", Proc. SPIE 10896, Solid State Lasers XXVIII: Technology and Devices, 108960K (7 March 2019); doi: 10.1117/12.2509978; https://doi.org/10.1117/12.2509978
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