ENGINEERABLE COMPRESSION OF ULTRASHORT PULSES BY USE OF 2ND-HARMONIC GENERATION IN CHIRPED-PERIOD-POLED LITHIUM-NIOBATE

We demonstrate the use of an aperiodic quasi-phase-matching (QPM) grat ing to generate second-harmonic pulses that are stretched or compresse d relative to input pulses at the fundamental frequency. We frequency doubled an externally chirped erbium-doped fiber laser generating 17-p s (FWHM) pulses at 1560 nm to produce near-transform-limited 110-fs (F WHM) pulses at 780 nm by use of a 5-cm-long lithium niobate crystal po led with a QPM grating chirped from an 18.2- to a 19.8-mu m period. (C ) 1997 Optical Society of America.