High Efficient LD End-pumped QCW 355 nm Laser

A laser diode( LD) end pumped acousto-optic Q-switched Nd∶ YVO4solid state 355 nm ultraviolet laser is reported by using intra-cavity double frequency and extra-cavity sum frequency technique. Nd∶ YVO4crystal bonded by YVO4in its both sides is end-pumped by LD,and typeⅠ phase matched LiB3O5( LBO) as the second harmonic generation crystal is placed in the cavity. 1 064 nm and 532 nm dual wavelength output from the cavity are coupled into the type Ⅱ phase matched LBO crystal through an achromatic lens. High efficiency,good beam quality and high repetition rate 355 nm ultraviolet laser is obtained by sum frequency mixing back and forth. The 4. 2 W 355 nm laser is obtained at the pump power of 28. 6 W and the repetition frequency of 20 kHz,with the pulse width as short as 20. 6 ns. The optical to optical conversion efficiency is about 14. 7%. The beam quality factor Mx 2and My 2of 355 nm ultraviolet laser are 1. 29 and 1. 23,respectively.