Double tungstate lasers: From bulk toward on-chip integrated waveguide devices

It has been recognized that the monoclinic double tungstates $KY{(WO_4)}_2$, $KGd{(WO_4)}_2$, and $KLu{(WO_4)}_2$ possess a high potential as rare-earth-ion-doped solid-state laser materials, partly due to the high absorption and emission cross sections of rare-earth ions when doped into these materials. Besides, their high refractive indexes make these materials potentially suitable for applications that require optical gain and high power in integrated optics, with rather high integration density. We review the recent advances in the field of bulk lasers in these materials and present our work toward the demonstration of waveguide lasers and their integration with other optical structures on a chip.