Q-switched laser

The high-repetition-rate Q-switching performance of the miniaturized LN Pockels cell  (www.wisoptic.com) was experimentally researched. At first, we studied the output performance of the Continuous Wave (CW) laser without any inserting elements. With an OC transmission of 20%, the optimized output power was achieved. Figure (a) below shows the output power as a function of the absorbed pumped power. At a pump power of 1.41 W, the maximum output power of 352 mW was obtained with a conversion efficiency of 25% and a threshold power of 0.6 W. When the miniaturized LN PC was inserted into the cavity, the threshold power increased and the output decrease slightly. By applying a high voltage pulse to the LN PC, a Q-switched laser is obtained. It should be noted that the applied voltage is only 280 V, which is much less than the quarter-wave voltage. This is because the hold-off state can be achieved as long as the cavity loss is slightly greater than the gain, so the full 90° round trip polarization rotation is usually unnecessary at low gain levels, which means that the full quarter-wave voltage may not always be required in the pulse-off regime. The dependence of the average output power on the pump power at various repetition rate is shown in figure (b) below. The output power increases both with the increase of the pump power and repetition rate. At a repetition rate of 15 kHz, the maximum output power was measured to be 230 mW with a pump power of 1.41 W, corresponding to a dynamic-static ratio of 65.3%. The output energy was stable with a variation of 6.3%. A plot of the output energy versus the repetition rate at a pump power of 1.41 W is presented in figure (c) below. The energy is almost invariable under 5 kHz, but decreased rapidly with the increase of the repetition rate above 5 kHz. A similar changing tendency can be found in literature. The results are consistent with the theoretical analysis.

 The performance of CW and Q-switched pulsed lasers