Control of near-infrared supercontinuum bandwidth by adjusting pump pulse duration

M Andreana,A Labruyère,P Leproux,D Giannone,A Tonello,Y Hernandez,S Hilaire,G Huss,V Couderc,S Wabnitz,A Bertrand,C Duterte,A Cserteg

doi:10.1364/oe.20.010750

Abstract

We experimentally and numerically investigated the impact of input pump pulse duration on the near-infrared bandwidth of supercontinuum generation in a photonic crystal fiber. We continuously stretched the temporal duration of the input pump laser (centered at 1030 nm) pulses from 500 fs up to 10 ps, while keeping fixed the pump peak power. We observed that the long-wavelength edge of the supercontinuum spectrum is increased by 200 nm as the pump pulse duration grows from 500 fs to 10 ps. We provide a quantitative fit of the experimental results by means of numerical simulations. Moreover, we have explained the observed spectral broadening enhancement induced by pump pulse energy by developing an approximate yet fully analytical model for soliton energy exchange through a series of collisions in the presence of stimulated Raman scattering.

Highlights

Optical supercontinuum (SC) generation is the nonlinear phenomenon whereby the spectrum of an intense pump beam, either pulsed or continuous wave (CW), is dramatically widened into a palette of wavelengths upon propagation in a nonlinear dispersive medium such as an optical fiber
Let us first describe our experimental study of the input pump pulse duration dependence of the SC spectral broadening
As a nonlinear medium for SC generation, we employed a sample of 8 m long photonic crystal fiber (PCF) with 5μm core diameter, 3μm hole-to-hole pitch and 0.5 air filling fraction

Summary

Introduction

Optical supercontinuum (SC) generation is the nonlinear phenomenon whereby the spectrum of an intense pump beam, either pulsed or continuous wave (CW), is dramatically widened into a palette of wavelengths upon propagation in a nonlinear dispersive medium such as an optical fiber. Since the early demonstrations of optical SC generation, it has been clear that the pump pulse duration plays a key role in determining the mechanism of nonlinear spectral broadening [1, 2]. When using relatively short pump pulses, one obtains high peak power and high repetition rate SC sources. A suitable combination of the pump pulse duration and group-velocity dispersion permits to select a specific nonlinear mechanism for activating frequency generation and spectral broadening in optical fibers With sub-ps pump pulses, even in the early stages of propagation one obtains multiple soliton fission and soliton self-frequency shift (SSFS) owing to Raman scattering. Whereas for relatively long (i.e., ns or sub-ns) pulses or CW, SC generation is first initiated by modulational instability (MI), followed by the formation and fission of a periodic soliton train [7]

Results

Discussion

Conclusion