Microchip Nd:YAG laser for safe laser applications

Abstract

For many applications, like micromanufacturing, remote sensing, data storage, etc. a microchip Nd:YAG laser is suitable. From the measurement of the laser radiation transmission through the eye tissue is evident that the injury probability of the retina is higher for the case of 1064 nm instead of 1338 nm. The main reason for that is the radiation water absorption. The Q-switched diode pumped (at 808 nm) microchip laser emitting radiation at wavelength 1338 nm was designed and realized. This laser was based on diffusion bonded crystal (diameter 5 mm) which combines in one piece the laser active part (Nd:YAG, 4 mm long) and saturable absorber (V:YAG, 0.7 mm, T₀ = 85%). The microchip resonator mirrors were deposited directly on the bonded crystal surfaces, output coupler reflexivity was 90%. The constructed "alignment-free" Q-switched microchip laser was tested under pulsed, and CW diode pumping. In both cases, the generated pulse energy, pulse length, emission wavelength, polarization, and laser beam profile were measured. The energy up to 18.6 &mgr;J in 1.7 ns long pulses was reached at the wavelength 1338 nm. TEM₀₀ laser mode was linearly polarized. The interaction of the radiation from the near- and mid-infrared region with the eye tissue was investigated and as conclusion the microchip with the wavelength 1338 nm was chosen as a good compromise between the eye safe 1.5 &mgr;m radiation and commonly, in the application used, 1.06 &mgr;m radiation.