RESUMO
We report an efficient deep-UV master-oscillator power amplifier (MOPA) laser system at 229â nm that generates 350 ps pulses at 2â MHz repetition rate with an average power of 1.2 W. The use of a polarization-maintaining large mode area neodymium-doped fiber operating on the 4F3/2â4I9/2 transition allows high-power laser emission of up to 28 W near 915â nm in the sub-nanosecond regime with low spectral broadening. Two nonlinear frequency conversion stages (LBO + BBO crystals) in a single-pass configuration directly convert the IR laser emission to deep UV. This laser demonstrates the great potential of Nd3+-doped fiber lasers to produce high-power deep-UV emission.
RESUMO
We present the first frequency-quadrupled linearly-polarized Q-switched neodymium-doped fiber laser generating > 500â mW average power at 226â nm. For this purpose, an amplified Q-switched oscillator using novel large-mode-area (LMA) fibers and generating up to 24 W average power (15â kW peak power) at 905â nm was developed. Two nonlinear frequency conversion stages using a LBO crystal for SHG and a BBO crystal for FHG generate respectively up to 4.9 W average power in the deep blue at 452â nm and a maximum of 510â mW average power in the deep ultra-violet (DUV) at 226â nm. Performance limitations and further improvements are discussed.