Efficient wavelength-tunable deep-diced ridge waveguide lasers in bulk Yb3+:CaF2 crystal

Abstract Channel (ridge) waveguides are produced in bulk 4.5 at.% Yb3+:CaF2 crystals by “deep” diamond saw dicing. They possess a rectangular profile with high aspect ratio (a width of 10–50 μm and a depth of 200 μm) and good verticality. The r.m.s. surface roughness of the diced side walls is only 0.5 nm. The waveguide propagation losses are as low as 0.13 ± 0.05 dB/cm at ~1 μm (for the 40 μm wide waveguide and TM-polarization) and they slightly increase for narrower structures. A continuous-wave Yb3+:CaF2 waveguide laser generated a maximum output power of 723 mW at 1029–1051 nm with a slope efficiency η of 76.0% (vs. the absorbed pump power), a laser threshold of 165 mW, and slightly multimode laser output (M2x = 1.05, M2y = 1.3). The waveguides exhibited lower propagation losses and better laser performance for TM polarized pump (as compared to TE polarized one). The laser emission was partially polarized. The waveguide laser allowed for continuous wavelength tuning between 1009 and 1072 nm (tuning range: 63 nm). The developed waveguides are promising for compact and integrated mode-locked sources at ~1 μm.