We present an enhanced technique for dispersion-free pulse shortening, which exploits the interplay of different third-order nonlinear effects in a waveguide structure. When exceeding a certain value of the pulse energy coupled into the waveguide, the typical oscillations of self-phase modulation (SPM)-broadened spectra vanish during pulse propagation. Such smoothed spectra ensure a high pulse quality of the spectrally filtered and, therefore, temporally shortened pulses independently of the filtering position. A reduction of the pulse duration from 138 to 24 ps has been achieved while preserving a high temporal quality. To the best of our knowledge, the nonlinear smoothing of SPM-broadened spectra is used in the context of dispersion-free pulse duration reduction for the first time.
© 2014 Optical Society of America
Original Manuscript: October 11, 2013
Manuscript Accepted: December 4, 2013
Published: January 23, 2014
R. Lehneis, C. Jauregui, A. Steinmetz, J. Limpert, and A. Tünnermann, "Smoothed spectra for enhanced dispersion-free pulse duration reduction of passively Q-switched microchip lasers," Opt. Lett. 39, 505-508 (2014)