LED-side-pumped Nd: YAG laser with >20% optical efficiency and the demonstration of an efficient passively Q-switched LED-pumped solid-state laser

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.