Abstract
The unique dispersive and nonlinear properties of air-silica microstructure fibers lead to supercontinuum generation at modest pulse energies. We report the results of a comprehensive experimental and numerical study of the initial stages of supercontinuum generation. The influence of initial peak power on the development of a Raman soliton is quantified. The role of dispersion on the spectral development within this pre-supercontinuum regime is determined by varying the excitation wavelength near the zero dispersion point. Good agreement is obtained between the experiments and simulations, which reveal that intrapulse Raman scattering and anti-Stokes generation occur for low power and short propagation distance.
Highlights
The large effective nonlinearity and near-visible zero group-velocity-dispersion (GVD) wavelength make air-silica microstructure fibers (ASMF) an ideal system for investigating and exploiting optical nonlinearities in fused-silica
This study provides an understanding of the fundamental nonlinear processes that dominate the spectral evolution in the low power (P0
The precise excitation center wavelength is of importance for supercontinuum generation since four-wave mixing (FWM) components may be phase matched for λ0 ≈ λZGVD
Summary
The large effective nonlinearity and near-visible zero group-velocity-dispersion (GVD) wavelength make air-silica microstructure fibers (ASMF) an ideal system for investigating and exploiting optical nonlinearities in fused-silica. The role of each distinct nonlinear effect during supercontinuum generation may be strongly dependent on the excitation pulse properties and the fiber dispersion. Quantifying this dependence is required if the generated supercontinuum is to be exploited. To this end, we have performed an experimental and numerical investigation of ultrashort pulse propagation in ASMF as a function of input peak power, P0, and excitation center wavelength, λ0. Where z is the direction along the fiber length, α is the absorption coefficient, βm is the mth dispersion coefficient, γ is the effective nonlinearity, ω0 is the pulse center frequency, fR is the relative strength of the Raman contribution and E(z,t) is the pulse complex temporal envelope. The simulation temporal and spectral resolution was typically δt=0.85 fs and δλ=0.31 nm respectively
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