Compositionally tuned 0.94-μm lasers: a comparative laser material study and demonstration of 100-mJ Q-switched lasing at 0.946 and 0.9441 μm

A new and innovative composite laser material Nd:YAG_xYSAG_1-x has been developed with several objectives in mind; tunability, efficiency, and minimization of the deleterious effects of amplified spontaneous emission (ASE) in Q-switched operation. Wavelength tuning to the requisite wavelength 0.9441 μm was achieved by using the technique referred to as compositional tuning; that is, using nonstoichiometric laser materials to shift the wavelength for precise tuning. Laser efficiency was achieved by studying the physics of 0.94-μm transitions in nonstoichiometric materials; i.e., by examining the effects of the host on the linewidth and cross section of of 0.94 μm neodymium (Nd) transitions, ASE was minimized by choosing materials with a small ratio of 1.06- to 0.94-μm peak cross sections. A comparative study of six different Nd-doped mixed garnet laser material systems was performed to meet the objectives above. Within these six material systems, over 20 laser materials were spectroscopically analyzed. The optimal laser material was found to be Nd:YAG_xYSAG_1-x, which has been demonstrated to lase at the preselected wavelength of 0.9441 μm, an important wavelength for remote sensing of water vapor. Operating this laser on the ⁴F_3/2→⁴I_9/2 transition in Nd:YAG_0.18YSAG_0.82 at 0.9441 μm, has produced for the first time over 100 mT in the Q-switched mode. This represents one of the few lasers that have been designed to operate at a specific, user-preselected wavelength