Anisotropy of nonlinear optical absorption of LBO crystals at 355 nm.

The dependence of the nonlinear optical absorption coefficients on the intensity and polarization of pulsed laser radiation at 355 nm was investigated for lithium triborate (LBO) crystals using the piezoelectric resonance laser calorimetry.

Hybrid booster at 1940 nm based on Tm:Lu2O3 ceramics implementing fiber combined signal and pump sources.

A novel concept of a booster amplifier for a pulsed Tm fiber laser at 1940 nm based on Tm:Lu2O3 ceramics and implementing fiber-combined signal and pump was examined. The pumping emission of the ceramics at 1678 nm was obtained from Raman-shifted Er fiber laser radiation. The hybrid fiber-ceramics amplifier with a gain factor of up to 6 dB and a pulse energy of more than 650 µJ with single-mode output was demonstrated.

Low-threshold mode instability in Yb3+-doped few-mode fiber amplifiers.

Spatio-temporal instability of the fundamental mode in Yb(3+)-doped few-mode PM fiber amplifiers with a core diameter of 8.5 µm was registered at 2-30 Watts pump power. Both experimental and theoretical analysis revealed the nonlinear power transformation of the LP(01) fundamental mode into high-order modes. Numerical simulation revealed self-consistent growth of the higher-order mode and traveling electronic index grating accompanying the population grating induced by the mode interference field (due to different polarizability of the excited and unexcited Yb(3+) ions). Experimental results and numerical calculations showed the increase of the instability threshold along with an increase of the signal frequency bandwidth.

Third harmonic frequency generation by type-I critically phase-matched LiB3O5 crystal by means of optically active quartz crystal.

We present a method of third harmonic generation at 355 nm by frequency mixing of fundamental and second harmonic radiation of an ytterbium nanosecond pulsed all-fiber laser in a type-I phase-matched LiB(3)O(5) (LBO) crystal where originally orthogonal polarization planes of the fundamental and second harmonic beams are aligned by an optically active quartz crystal. 8 W of ultraviolet light at 355 nm were achieved with 40% conversion efficiency from 1064 nm radiation. The conversion efficiency obtained in a type-I phase-matched LBO THG crystal was 1.6 times higher than the one achieved in a type-II LBO crystal at similar experimental conditions. In comparison to half-wave plates traditionally used for polarization alignment the optically active quartz crystal has much lower temperature dependence and requires simpler optical alignment.