The prospects of monoclinic Yb:KLu(WO4)2 crystal for multi-watt microchip lasers

The concept of Yb-doped double tungstate microchip lasers is verified and scaled to the multi-watt power level. The active element is a 2.6 mm-thick Yb:KLuW crystal cut along the Ng optical indicatrix axis. Maximum continuous-wave output power of 4.4 W is extracted at 1049 nm with a slope efficiency of 65% and an optical-to-optical efficiency of 44% with respect to the absorbed pump power. The laser emission is linearly polarized and the intensity profile is characterized by a near-circular TEM00 mode with Mx,y < 1.1. Due to low intracavity losses of the microchip laser, laser operation at wavelengths as long as 1063 nm is achieved. The mechanism of the thermal mode stabilization in the microchip cavity is confirmed. At very low resonator losses polarization-switching between E || Nm and Np oscillating states is observed and explained on the basis of spectroscopic and thermal lens characteristics. 2014 Optical Society of America OCIS codes: (140.3380) Laser materials; (140.6810) Thermal effects; (140.3480) Lasers, diodepumped. References and links 1. J. J. Zayhowski and A. Mooradian, “Single-frequency microchip Nd lasers,” Opt. Lett. 14, 24–26 (1989). 2. J. J. Zayhowski and C. Dill III, “Diode-pumped passively Q-switched picosecond microchip lasers,” Opt. Lett. 19, 1427-1429 (1994) 3. T. Taira, A. Mukai, Y. Nozawa, and T. Kobayashi, “Single-mode oscillation of laser-diode-pumped Nd:YVO4 microchip lasers,” Opt. Lett. 16, 1955-1957 (1991). 4. V. Petrov, M. C. Pujol, X. Mateos, O. Silvestre, S. Rivier, M. Aguiló, R. M. Solé, J. Liu, U. Griebner, and F. Díaz, “Growth and properties of KLu(WO4)2, and novel ytterbium and thulium lasers based on this monoclinic crystalline host,” Laser & Photon. Rev. 1, 179–212 (2007). 5. M. Pollnau, Y. E. Romanyuk, F. Gardillou, C. N. Borca, U. Griebner, S. Rivier, and V. Petrov, “Double tungstate lasers: from bulk toward on-chip integrated waveguide devices,” IEEE J. Select. Topics Quantum Electron. 13, 661–671 (2007). 6. X. Mateos, R. Sole, Jna. Gavalda, M. Aguilo, J. Massons, F. Diaz, V. Petrov, and U. Griebner, “Crystal growth, spectroscopic studies and laser operation of Yb-doped potassium lutetium tungstate,” Opt. Mat. 28, 519–523