CW Laser Operation of ${\hbox {KLu}}_{0.945}{\hbox {Tm}}_{0.055}({\hbox {WO}}_{4})_{2}{\hbox {–KLu}}({\hbox {WO}}_{4})_{2}$ Epilayers Near 2 $\mu{\hbox {m}}$

Thin epilayers of monoclinic ${\hbox {KLu}}({\hbox {WO}}_{4})_{2}$ doped with thulium are grown by liquid phase epitaxy on undoped ${\hbox {KLu}}({\hbox {WO}}_{4})_{2}$ substrates. The epitaxial composites are optically characterized and implemented in a cavity, longitudinally pumped (normal to the layer) by a Ti:sapphire laser. Tunable (1894–2039 nm) continuous-wave laser operation is achieved with maximum slope efficiency as high as 64% with respect to the absorbed pump power at 802 nm. The output power is limited by the crystal absorption.