Supercontinuum Generation in Silica Fibers by Amplified Nanosecond Laser Diode Pulses

Supercontinuum (SC) with a continuous spectrum from ~0.8-3 mum is generated in a standard single-mode fiber followed by high-nonlinearity fiber. The SC is pumped by 2-ns laser diode (LD) pulses amplified in a multistage fiber amplifier, and the two octave spanning continuum is achieved by optimizing a two-stage process that separates pulse breakup and soliton formation from spectral broadening. We also demonstrate scalability of the average power in the continuum from 27 mW to 5.3 W by increasing the pulse repetition rate from 5 kHz to 1 MHz, while maintaining comparable peak power. We attribute the generated SC spectrum to the ensemble average of multiple solitons and the superposition of their corresponding spectra. The hypothesis is confirmed through simulation results obtained by solving the generalized nonlinear Schrodinger equation (NLSE). Similar SC spectra can also be obtained by using both femtosecond and nanosecond pump pulses. Furthermore, by tailoring the input pulse shape, we propose and simulate the generation of the entire SC spectrum in one single soliton under quasi-continuous-wave (CW) pulse pumping scheme.