Green picosecond narrow-linewidth tapered fiber laser system

We present a single-mode narrow band linear-polarized picosecond green fiber source delivered up to 146.4 kW of peak power. The laser architecture is composed of frequency-doubled all-fiber MOPA system operating at 1064 nm. The commercially available gain-switched semiconductor laser diode was used as a seed source delivered 77 ps pulses with the repetition rate between 100 kHz - 80 MHz. Two stages of pre-amplifiers based on the single-mode Yb-doped fibers were designed to amplify microwatt pulsed signal up to milliwatt level. A high-power amplification cascade comprised a double-clad polarization-maintaining tapered Yb3+-doped fiber as a gain medium. The frequency doubling was realized in a single-pass scheme with LBO crystal. The MOPA design with the active tapered fiber enabled to amplify effectively a narrowband picosecond IR radiation with relatively small spectral broadening. We obtained stable laser radiation with 77 ps pulses at repetition rate of 1 MHz, 290 pm spectral bandwidth with a central wavelength of 532 nm, the average power of 12 W corresponding to 12 μJ of pulse energy and 146.4 kW of peak power. The overall efficiency of secondharmonic generation reached 37 % in a single pass scheme. The obtained results showed advantages of the MOPA system based on a tapered amplifier in comparison with already published picosecond green laser systems exploited standard amplifiers based on cylindrical fixed-core fibers. The single-mode green laser with high peak power and narrow line are in high demand for a wide range of Raman spectroscopy applications.