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Wigner transform approach to dynamic-variable partially coherent laser beam characterization

Jabczyński J., Gontar P., Gorajek Ł.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2020

Vol. 68, nr 1

141--146

1) Background: the modeling, characterization, transformation and propagation of high-power CW laser beams in optical (including fiberoptic) trains and in the atmosphere have become hot topics in laser science and engineering in the past few years. Single-mode output is mandatory for high-power CW laser applications in the military field. Moreover, an unstationary, dynamic operation regime is typical. Recognized devices and procedures for laser-beam diagnostics could not be directly applied because of dynamic behavior and untypical non-Gaussian profiles. 2) Methods: the Wigner transform approach was proposed to characterize dynamically variable high-power CW laser beams with significant deterministic aberrations. Wavefront-sensing measurements by means of the Shack-Hartmann method and decomposition into an orthogonal Zernike basis were applied. 3) Results: deterministic aberration as a result of unstationary thermal-optic effects depending on the averaged power of the laser output was found. Beam quality determined via the Wigner approach was changed in the same way as the measurements of the beam diameter in the far field. 4) Conclusions: such an aberration component seems to be the main factor causing degradation in beam quality and in brightness of high-power CW laser beams.

High repetition rate, tunable, Q-switched diode pumped Tm:YLF laser

Gorajek Ł., Jabczyński J. K., Żendzian W., Kwiatkowski J., Jelinkova H., Sulc J., Nemec M.

Opto-Electronics Review

2009

Vol. 17, No. 4

309-317

The aim of work was to characterize a simple oscillator consisted of Tm:YLF crystal end-pumped by a fiber coupled diode laser and active Q-switch with tunability option. About 7 W with near 35% slope efficiency was demonstrated in a free-running mode. The divergence angle was about 4.3 mrad and estimated parameter M² < 1.3. Continuous tuning by means of Lyot's filter, consisted of 2 quartz plates in the range of 1879.0-1939.4 nm with less than 1-nm linewidth, was achieved. For the best case (10-ms pump pulse duration, 42-A pump current corresponding to 266 mJ of pump energy) , the Q-switched energy was 10.5 mJ with pulse duration of 22 ns corresponding to near 0.5 MW peak power. The 2.5 W of average power with 12.6-kW peak power and 2000-Hz repetition rate was demonstrated for cw pumping regime.