Abstract

We have designed and demonstrated two wide bandwidth frequency doublers capable of instantaneous second harmonic generation over the entire 100 nm cavity optics bandwidth of a passively mode locked Ti:Al₂O₃ laser with no loss of conversion efficiency. Instantaneous phase matching over a large bandwidth is achieved passively by the use of dispersive optics prior to focussing the fundamental in the nonlinear crystal. Our first design, utilizing a prism pair geometry to achieve phase matching, has demonstrated constant conversion efficiency over a 100 nm bandwidth. The theoretical conversion bandwidth extends across the entire Ti:Al₂O₃ gain bandwidth. This frequency doubler exhibits net negative group velocity dispersion that significantly broadens sub-100-fs pulses. Our second design, based on a prism-lens combination for the dispersive optics, exhibits a similarly broad bandwidth that also theoretically spans the entire laser bandwidth. This design, however, has demonstrated no pulse broadening because of negative group velocity dispersion for input pulses as short as 90 fs. This type of dispersive frequency doubler may have widespread uses in broadly tunable pulsed sources such as free electron lasers.

© 1992 Optical Society of America