Continuous-Wave and Passive Q-Switching Laser Performance of Yb:YCa O(BO )

We have conducted an investigation into the continuous-wave (CW) and passive Q-switching laser performance of the Yb:YCa₄O(BO₃)₃ (Yb:YCOB) crystal, aiming to evaluate its capability of power or energy scaling in compact end-pumped lasers. Efficient CW laser operation was realized with output coupling changed over a wide range from 0.4% to 60%. Operating in CW mode in the long-wavelength sideband around 1085 nm, the Z-cut Yb:YCOB laser produced an output power of 10.7 W with an optical-to-optical efficiency of 56%; in CW operation of the Y-cut Yb:YCOB laser oscillating in the main emission band, an output power of 17.0 W was reached, with optical-to-optical and slope efficiencies being respectively 62% and 78% (with respect to incident pump power). In passive Q-switching regime, the X-cut crystal proved to be the most advantageous in generating high average power and high pulse energy. With a Cr⁴⁺:YAG crystal plate serving as saturable absorber whose initial transmission was T₀ = 97.5%, and with an output coupling of T = 20%, an average output of 10.72 W was generated at a pulse repetition rate of 26.3 kHz, the resulting pulse duration was 22.3 ns. While under Q-switching operational conditions of T₀ = 90.0% and T = 40%, a maximum average output power of 4.13 W could be reached at a rather low repetition rate of 3.23 kHz, yielding a pulse energy that was as high as 1.28 mJ, the resulting pulse duration and peak power being 5.0 ns and 256 kW, respectively.