Abstract
Femtosecond lasers and optical supercontinua offer wide optical bandwidths but at the same time suffer from low spectral brightness. One solution is to perform external laser spectral compression. Our approach for spectral compression is using a linear ramp dispersion-increasing fiber (DIF), which is reverse processes of adiabatic soliton temporal compression. However, to date, laser spectral compressions have been limited in generating a single output spectrally compressed peak. We demonstrate the generation of spectrally compressed spectrum with dual peaks. Moreover, the relative amplitudes and wavelengths of the two spectral peaks are adjustable through the average power, input pulse chirp condition. The experimental results are compared to simulations and are found in excellent agreements.