Fluorescence feedback control of an active Q-switched diode-pumped Nd:YVO4 laser

Cavity-dumped Yb:YAG ceramic in the 20 W, 12 mJ range at 6.7 ns operating from 20 Hz to 5 kHz with fluorescence feedback control

Increasing data acquisition rates in metrology applications based on optical parametric oscillators (OPOs) can accelerate measurement processes. To achieve this, flash-lamp systems with low pulse repetition frequencies of 10-100 Hz used as a pump source for the OPOs could be replaced by diode-pumped solid-state lasers in the kHz range. We demonstrate a 969 nm pumped Yb:YAG ceramic laser yielding 21.6 W output power, 12.5 mJ pulse energy, and excellent beam quality. Fluorescence feedback control, developed from gain dynamics simulations in two operating regimes, allows stable operation at 6.7 ns from 20 to 5000 Hz. Third harmonic generation to 343 nm yields 3.24 W at 2 kHz. The system provides constant pulse duration in a huge repetition rate interval, which is beneficial for pump sources for future metrology devices.

Control of Q-switched mode locking by active feedback

It is demonstrated that Q-switching dynamics in mode-locked lasers can be controlled by use of an active feedback loop. Analytic design rules for the feedback loop are presented. Suppression of Q-switched mode locking in a diode-pumped, passively mode-locked Nd:YVO(4) laser is shown experimentally and numerically.

Influence of the thermal effect on the TEM00 mode output power of a laser-diode side-pumped solid-state laser

A fraction of pump power has been converted to TEM00 mode laser power for a side-pumped solid-state laser by use of a space-dependent rate equation. We investigated the pump-to-mode (TEM00) ratio when scaling laser-diode side-pumped solid-state lasers to high-power levels by including the thermal effect in the space-dependent rate equation. Based on the assumption that Gaussian pump power is the same at any cross section of a laser rod, we resolved the output power with a space-dependent rate equation; temperature distribution in the laser rod was obtained; the optical path difference distribution was derived, and we estimated the diffraction losses that result from thermally induced spherical aberration by use of the Strehl intensity ratio. We determined that thermally induced diffraction losses are strongly dependent on pump power and on the pump-to-mode ratio.