Researchers compress fiber-generated continuum to produce shortest femtosecond pulses

Researchers compress fiber-generated continuum to produce shortest femtosecond pulses

Douwe A. Wiersma and associates from the Ultrafast Laser and Spectroscopy Laboratory at the University of Groningen in the Netherlands have generated 5-fs pulses from a Ti:sapphire laser, reportedly breaking the 6-fs record set in 1987 by scientists at AT&T Bell Laboratories. Compression of a white-light continuum, generated by launching 13-fs pulses from a cavity-dumped Ti:sapphire laser into a short piece of single-mode polarization-preserving fiber, in a conventional grating-prism compressor shortened the pulses to 4.9 fs. A novel prism-chirped mirror compressor produced pulses of 5.5 fs. Wiersma suggests that pulses of 4 fs may be feasible with custom-designed chirped mirrors. With a pulse energy of about 6 nJ at u¥to a 1-MH¥repetition rate, the 5-fs pulses are suitable for a variety of ultrafast optical experiments on condensed phase systems. Wiersma acknowledges that ultrashort-pulse generation based on pulse-chirping in a fused-silica fiber is possible only for pulse energies of ~50 nJ. Higher-intensity ultrashort pulses may possibly be achieved by pulse chirping in a hollow fiber (see Laser Focus World, Sept. 1996, p. 15).