Highly efficient dual-wavelength laser operation of cryo-cooled resonantly (in-band) pumped Ho3+:YVO4 laser.

We have demonstrated a CW, multiwatt, dual-wavelength cryogenically cooled, resonantly (in-band) pumped Ho(3+):YVO(4) laser with nearly quantum-defect-limited performance. The Ho(3+)(2%):YVO(4) gain element, which was maintained at ~80 K and pumped by a Tm-fiber laser at 1966 nm, emitted at wavelengths of either 2053 or 2068 nm, or both at the same time, depending on the outcoupling loss and the pump power. We have achieved laser operation with a maximum slope efficiency of ~92%. This is, to the best of our knowledge, the highest slope efficiency ever demonstrated for any Ho(3+)-doped laser.

Resonantly diode-pumped Ho3+:Y2O3 ceramic 2.1 µm laser.

We report what is believed to be the first laser operation based on Ho3+-doped Y2O3. The Ho3+:Y2O3 ceramic was resonantly diode-pumped at ~1.93 µm to produce up to 2.5 W of continuous wave (CW) output power at ~2.12 µm. The laser had a slope efficiency of ~35% with respect to absorbed power and a beam propagation factor of M2 ~1.1. We have measured the absorption and stimulated emission cross sections of Ho3+:Y2O3 at 77 K and 300 K and present the calculated gain cross section spectrum at 77 K for different excited state inversion levels.

Composite Yb:YAG/SiC-prism thin disk laser.

We report the first demonstration of a Yb:YAG thin disk laser wherein the gain medium is intracavity face-cooled through bonding to an optical quality SiC prism. Due to the particular design of the composite bonded Yb:YAG/SiC-prism gain element, the laser beam impinges on all refractive index interfaces inside the laser cavity at Brewster's angles. The laser beam undergoes total internal reflection (TIR) at the bottom of the Yb(10%):YAG thin disk layer in a V-bounce cavity configuration. Through the use of TIR and Brewster's angles, no optical coatings, either anti-reflective (AR) or highly reflective (HR), are required inside the laser cavity. In this first demonstration, the 936.5-nm diode pumped laser performed with approximately 38% slope efficiency at 12 W of quasi-CW (Q-CW) output power at 1030 nm with a beam quality measured at M(2) = 1.5. This demonstration opens up a viable path toward novel thin disk laser designs with efficient double-sided room-temperature heatsinking via materials with the thermal conductivity of copper on both sides of the disk.