“…Moreover, like in most Yb 3+ -doped laser hosts, additional advantages are low quantum defects, relatively high doping concentrations without significant lifetime quenching, and readily available high-brightness pumping diode lasers for end pumping. As a result, efficient microcavity cw lasers [1], tunable lasers [2,3], and mode-locked lasers have been realized in monoclinic and tetragonal double tungstates [4,5]. Furthermore, the monoclinic double tungstates such as KY͑WO 4 ͒ 2 , KGd͑WO 4 ͒ 2 (KGW), and KLu͑WO 4 ͒ 2 have highly anisotropic optical, mechanical, and thermal properties [6,7].…”