Broadband (0.6-1.8-microm) subnanosecond pulse emission using an ultra-low-loss single-mode fiber

A fiber Raman laser generating a subnanosecond pulse in the extremely broad spectral region between 0.6 and 1.8 microm has been developed using an ultra-low-loss single-mode fiber as the generating medium, pumped by a high-power mode-locked and Q-switched Nd:YAG laser at lambda = 1.06 microm. The fiber length dependence of the Raman emission is investigated by varying the generating fiber length from several meters to ~1 km. As a result, pulses with 3-dB widths <0.4 nsec are obtained in the 1.0-1.7-microm spectral region by using an ~200-m long generating fiber with a pump peak power of 0.4 kW. Timing jitter occurring in the displayed pulse train on an oscilloscope is reduced to +/-0.02 nsec with the newly constructed delay system.