Watt-level ultrafast laser inscribed thulium waveguide lasers

• DOI: 10.1016/j.pquantelec.2020.100266
• Publication Date: 2020-05-24T15:26:13Z
• Authors: Esrom Kifle; Pavel Loiko; Carolina Romero; Javier Rodríguez ...; Magdalena Aguiló; Francesc Díaz; Patrice Camy; Uwe Griebner; Valentin Petrov; Xavier Mateos
• Keywords: [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics]; 0103 physical sciences; [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]; 530; 01 natural sciences; 7. Clean energy; 620

Spanish Government, MINECO (MAT2016-75716-C2-1-R (AEI/FEDER,UE), FIS2017-87970-R); Junta de Castilla y León (SA287P18); Generalitat de Catalunya (2017SGR755).<br/>We report on the first watt-level ultrafast laser inscribed Thulium waveguide (WG) lasers. Depressed-index buried channel WGs with a circular cladding (type III) are produced in monoclinic Tm3+:KLu(WO4)2 crystals. Laser operation is achieved under conventional (3H6 → 3H4) and in-band (3H6 → 3F4) pumping. In the former case, employing a Raman fiber laser emitting at 1679 ​nm as pump, the continuous-wave Tm channel WG laser generated 1.37 ​W ​at 1915–1923 ​nm with a record-high slope efficiency of 82.7% (with respect to the absorbed pump power), a threshold of only 17 ​mW and a spatially single-mode output with linear polarization. The WG propagation losses were 0.2 ​± ​0.3 ​dB/cm. Passive Q-switching of Tm channel WG lasers is achieved using Cr2+:ZnS and Cr2+:ZnSe saturable absorbers. With Cr2+:ZnS, record-short pulses of 2.6 ns/6.9 ​μJ ​at a repetition rate of 8.0 ​kHz were generated. The developed WGs are promising for compact GHz mode-locked lasers at ~2 ​μm.<br/>