Abstract

Ultrashort optical pulses in the regime of 10 fs or less are very susceptible to frequency-dependent phase errors as a result of their large bandwidth. We have designed, constructed, and tested devices which provide negative quadratic group delay correction (cubic phase) in a broadband centered about 620 nm. These devices are Gires-Tournois interferometers¹ which we operate exactly on the first resonance, consisting of a single high index layer of TiO₂, 70.1 nm thick, on specifically selected low dispersion broadband high efficiency substrates in S polarization. We have selected two kinds of substrate for their broadband high reflectance and low frequency-dependent group delay errors: single-stack dielectrics, and thin dielectric stacks on metal films. The substrates are critical to the device operation. We measure the frequency dependence of the group delay with 1-fs accuracy using a white-light interferometric technique.² These devices will be useful for ultrashort pulse generation, compression, and measurement applications.

© 1988 Optical Society of America