Femtosecond autocorrelation of CW-modelocked pulses from 416-630 nm using a GaN laser diode

Summary form only given. Sensitive second-order optical autocorrelation measurements of CW-modelocked ultrashort pulses have been demonstrated at a number of wavelengths in the near- and mid-IR using the two-photon response of semiconductor devices but the spectral region which had until now remained difficult to access using two-photon measurement techniques was the visible, principally because of the lack of suitable detectors in which the two-photon response dominated the residual linear response at wavelengths above the bandgap wavelength. Improvements in the quality of GaN semiconductors have resulted recently in the successful fabrication of laser diodes from this material which are now available on a commercial basis. Using one such laser diode with a nominal emission wavelength of 393 nm (Nichia NLHV500) we have found a strong two-photon response across a range of visible wavelengths which has enabled sensitive measurement of intensity and interferometric second-order autocorrelations.