Optical pulse compression to 8 fs at a 5-kHz repetition rate

Using self-phase modulation in a single-mode optical fiber, single amplified 40-fs optical pulses are compressed to 8-fs duration at a 5-kHz repetition rate. The pulse has a center wavelength at 620 nm, a spectral bandwidth of 70 nm, and a full width half-maximum corresponding to a duration of less than four optical periods. The spectrum of the pulse, after passing through the fiber and some diffraction grating is given as a function of excitation intensity. The measured autocorrelation function of the compressed pulse is shown and the FWHM is 8 fs. The length of the optical fiber is found to be 7 mm which indicates that at intensities above 10 to the 12th W/sq cm in the core of the optical fiber, complicating nonlinear processes in addition to self-phase modulation may be significant.