Power-scaled CW Alexandrite lasers

We present several strategies for increasing the output laser power of near-diffraction limited continuous-wave Alexandrite lasers pumped by fibre-coupled red laser diodes. Laser mode size control using a convex mirror with the varying thermal lens is shown to be an efficient method for generating record levels of output power from a diode-pumped Alexandrite laser. 8.6 W is obtained with M²<1.1 M 2 < 1.1 and an optical efficiency of 27%. 735–790 nm wavelength tuning is demonstrated with > 2.5\,W > 2.5 W and a record dual-wavelength output power of 4.2 W. In a ring-cavity geometry, 5.1 W is obtained with M²<1.1 M 2 < 1.1 showing promising potential for multi-watt single-longitudinal-mode operation. Detailed laser cavity modelling including thermal lens analysis is also provided.