Ceramic broadband materials for HAPP Lasers at HiLASE

Development of high average and peak power (HAPP) lasers requires laser materials with broad emission bands along with good thermo-mechanical and thermo-optical properties.

Yb doped YAG shows excellent properties at cryogenic temperature which make them attractive material for such lasers. Nevertheless, at cryogenic temperature Yb:YAG exhibit very narrow bandwidth which limits the pulse width of Gaussian transform-limited pulses to pico-second. To address this limitation, we have introduced some disorder in the regular lattice to achieve inhomogeneous broadening in the emission spectra. Yb:Y3(Al1-yGay)5O12 ceramic pellets of Yb:YAG admixed with different concentrations of Gd3+ and Ga3+ were prepared by high temperature solid-state reaction. Cubic nature of YAG is maintained even in admixed samples and is confirmed by the XRD patterns. Cryogenic emission spectra at 100K showed a significant broadening at the prominent emission peak at 1030 nm for Ga3+ admixed Yb:YAG samples whereas the broadening is weaker in Gd3+ admixed Yb:YAG. Such a broadening is necessary for sub picosecond pulse lasers operating at cryogenic temperature. Future work will be focused on studying the effect of higher concentrations (50 to 60%) of gallium and also addition of other cations such as scandium at cryogenic temperature.