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

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 mu m and a depth of 200 mu m) 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 similar to 1 mu m (for the 40 mu m 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 eta of 76.0% (vs. the absorbed pump power), a laser threshold of 165 mW, and slightly multimode laser output (M-x(2) = 1.05, M-y(2) = 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 similar to 1 mu m.

Automated summary

Channel waveguides with high aspect ratio are produced in Yb3+:CaF2 crystals by deep diamond saw dicing, exhibiting good verticality and low propagation losses. A Yb3+:CaF2 waveguide laser shows high slope efficiency, low laser threshold, slightly multimode laser output, and continuous wavelength tuning between 1009 and 1072 nm. The developed waveguides have potential for compact and integrated mode-locked sources at around 1 µm.