Visible supercontinuum generation in photonic crystal fiber using various harmonics of subnanosecond Q-switched laser

Abstract

We report results of supercontinuum generation in highly nonlinear polarization maintaining photonic crystal fiber (PCF) using the first or second harmonics of a subnanosecond passively Q-switched Nd:YAG microlaser. The Nd:YAG microlaser generated 50 μ J energy 300 ps duration pulses at 1064 nm with a kilohertz repetition rate. We demonstrated that we can expand the supercontinuum spectrum to cover the whole visible range and beyond using either first or second harmonics of our pump laser in the case of such pump pulse durations. In the case of a first-harmonic pump ( λ p = 1064 nm ), the supercontinuum extended from 400 to 1300 nm and in the case of a second-harmonic pump ( λ p = 532 nm ), it extended from 400 to 900 nm. In addition, we compared the supercontinuum evolution and dependence on pump pulse energy in both cases. We also performed numerical simulations of supercontinuum generation in PCF using an improved approach. The generalized nonlinear Schrodinger equation was modified so that numerical simulations would yield greater accuracy in the case of longer (300 ps) pulses. The simulated supercontinuum spectra display the same qualitative features as that measured in the experiment.