High-energy Alexandrite picosecond laser using the self-injection technique

High-energy ultrashort pulse lasers have been developed in a variety of applications such as medical treatment, defense, semiconductor and manufacturing. In terms of aesthetic dermatology, Alexandrite (Cr³⁺:BeAl₂O₄) lasers have an attractive and useful wavelength band (700 nm to approximately 800 nm). Therefore, Alexandrite lasers with shorter pulses and higher energy are required in the medical device market. Since alexandrite medium has a low energy gain at room temperature, it is not easy to make a flash-pumped picosecond alexandrite laser that produces sufficiently high output energy. To generate high-power picosecond laser pulses, we used self-injection and ultra short pulse generation techniques including Q-switching, mode-locking and cavity dumping. We have developed picosecond 755 nm alexandrite laser which can be operated at pulse width in the range from 600 to 2000 ps. A maximum average output energy of 400 mJ was achieved in the picosecond regime.