Spectral compression of femtosecond pulses in photonic crystal fiber with anomalous dispersion

We present a numerical investigation of nonlinear propagation of chirp-free femtosecond pulses at 1550-nm wavelength in a nonlinear photonic crystal fiber (PCF) with anomalous dispersion. The PCF has a second-order dispersion of − 8.67 ×104 fs²/m, third-order dispersion of 2.8×10⁵ fs³/m and nonlinear coefficient of 11 W⁻¹km⁻¹ at 1550 nm. The simulation results show that efficient spectral compression of unchirped ultrashort pulses is induced in PCF when the input pulse parameters satisfy the condition 0.6 ≪ N ≪ 0.7 for the soliton number N. It is found that the compressed spectral width is strongly dependent on the initial peak power and propagation length of the incident pulse. A compression factor up to 7 can be achieved. With the PCF, efficient spectral compression can take place in the wavelength range of 1530 ∼ 1570 nm covering the C-band. This spectral-compression scheme offers much promise for laser spectroscopy, optical information technologies and high-power fiber-laser systems.