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Alexandrite laser in Q-switched single longitudinal mode operation pumped by a fiber-coupled diode module

: Munk, A.; Jungbluth, B.; Strotkamp, M.; Hoffmann, D.; Poprawe, R.; Höffner, J.


Clarkson, W. Andrew (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Solid State Lasers XXVIII. Technology and Devices : 5-7 February 2019, San Francisco, California, United States
Bellingham, WA: SPIE, 2019 (Proceedings of SPIE 10896)
ISBN: 978-1-5106-2434-4
ISBN: 978-1-5106-2435-1
Art. 1089610, 9 S.
Conference "Solid State Lasers - Technology and Devices" <28, 2019, San Francisco/Calif.>
Industrial Laser, Laser Source and Laser Applications Conference (LASE) <2019, San Francisco/Calif.>
Bundesministerium fur Wirtschaft und Energie BMWi (Deutschland)
FKZ 50RP1605
Fraunhofer ILT ()

In this work a diode-pumped Q-switched Alexandrite laser operating in single longitudinal mode (SLM) at the potassium resonance line is presented. The self-developed laser diode pump device is fiber-coupled ( = 400μm, NA=0.22) and delivers a pump energy of 18 mJ at 636 nm with a pulse duration of 120 μs and a repetition rate of 500 Hz. Pump light not absorbed in single-pass through the 7 mm long crystal is recollimated, polarization adjusted and refocused into the crystal. The Alexandrite laser yields a pulse energy of 1.7 mJ at a repetition rate of 500 Hz with a high pulse-to-pulse stability of 0.2 % (rms) and a beam quality of M2 < 1.1 in both spatial directions. The output beam is round and stigmatic without further beam shaping. The electro-optical efficiency of the laser system is 2 % which is approximately two magnitudes higher than of comparable flashlamp-pumped Alexandrite laser systems. By seeding the resonator with a SLM diode laser and actively stabilizing the cavity length, SLM-operation at the resonance line of potassium at 769.898 nm with a linewidth of approximately 10 MHz is achieved. Thereby the laser fulfills all the requirements for a resonance-lidar system. The investigations presented in this publication show the feasibility for pumping a complex ring resonator with a fibercoupled pump module in the red spectral region. This presents an important step to compact lidar systems for autonomous measurements under rough environmental conditions.