The aim of this work is to develop tunable Alexandrite lasers, particularly focusing on generating notable Q-switched pulses and frequency-doubling with high energy and a widely tunable wavelength range for a variety of applications.

Diode-pumped continuous-wave (CW) Alexandrite lasers are presented, with various laser cavity designs and pump arrangements. Lasers with high power, high slope efficiency, a wide tuning range, and good beam quality are achieved with single- and dual-end pumping from fibre-delivered and free-space diode modules. Side-pumped Alexandrite lasers are demonstrated with laser cavities of linear and bounce geometry, and single-pass and double-pass pump arrangements.

Diode-pumped electro-optic (EO) and acousto-optic (AO) Q-switched Alexandrite lasers are investigated. The first ever AO Q-switched diode-pumped Alexandrite laser with a broad tuning range from 719 to 787 nm is presented, achieving remarkable high pulse energy of 2.6 mJ, short pulse duration of 75 ns, and high pulse peak power of 35 kW. This development is of great interest in numerous fields, such as laser medicine, lidar systems, and photoacoustic imaging.

Second harmonic generation (SHG) based on the EO and AO Q-switched Alexandrite lasers is produced, offering UV pulses with high pulse energy of 0.66 mJ, high conversion efficiency of 32.9\%, and broad tunability from 361 to 391 nm. The widely tunable frequency-doubled UV has great potential in multiple applications including biomedical analyses and laser-based lidar systems.