Continuous-wave and passively mode-locked alexandrite lasers pumped at 532 nm

Abstract

Alexandrite crystal (Cr-ion doped chrysoberyl, Cr3+: BeAl2O4) is an attractive gain medium for producing ultrashort laser pulses. Alexandrite properties are similar to those of the Ti:sapphire crystal, which is the most widely used crystal for creating ultrashort pulses. Therefore, Alexandrite can be a good candidate for development of ultra-short pulse lasers. To date, the generation of femtosecond pulses from an Alexandrite laser has not been reported. The primary aim of this research was to create an ultrashort pulse Alexandrite laser. In the first stage of this research, a continuous- wave Alexandrite laser was designed, built and optimized to provide maximum output power. Also, its laser beam quality and wavelength tuning range using a single plate birefringent filter was measured. In addition, the basic behavior of the laser to determine its thermal lensing was investigated. Furthermore, a dual-wavelength operation using several single plate birefringent filters was demonstrated for the first time. In the second stage of this research, ultrashort pulses of 420 fs and 380 fs duration from a quantum-dot saturable absorber mode-locked Alexandrite laser were obtained for the first time. Finally, a femtosecond Kerr-lens mode-locked Alexandrite laser that produced 170 fs long pulses was created for the first time. These results can lead to the development of efficient ultrafast Alexandrite oscillators and amplifiers that can replace widely used inefficient and costly Ti:sapphire laser systems.