ABSTRACT
An efficient LED pumping module is explored for the demonstration of energy scaling of passively Q-switched output to millijoule high-pulse-energy level. For the free-running operation at fundamental wavelength, the highest optical conversion efficiency of 23.7% is reached. By using a Cr4+:YAG crystal as the saturable absorber, the passively Q-switched output energy is up to 14.5 mJ in a compact setup. The laser resonator is further optimized to shorten the output pulse width and to obtain better mode quality. The pulse width of the Q-switched emission is as short as 25 ns, and the peak power is up to 0.7 MW. With such a highly efficient configuration, the extracavity second-harmonic generation at 532 nm can be achieved with 4.5 mJ pulse energy.
ABSTRACT
A LED-array-pumped Nd:YAG laser with optical conversion efficiency up to 20.2% is demonstrated by direct side-pumping without a coupling lens. The 810-nm LED array with a full-width-half-maximum of 30 nm and an area fill factor of 50% is designed to attain high spectral absorption efficiency with a pump density of 151.8 W/cm2. Furthermore, higher than 45% overall coupling efficiency is achieved by placing the LED array as close as possible to the side of the gain medium for overcoming the large pumped divergence. More importantly, by using the efficient pump scheme, the demonstration of a passively Q-switched LED-pumped laser is successfully realized with a pulsed energy of 1.42 mJ.