Abstract

Two-photon-excited fluorescence (TPEF) was one of the first original techniques to measure the duration of ultrashort laser pulses.¹ In the following the TPEF was pushed to the side by the more efficient method of second-harmonic generation in a nonlinear crystal, where the additional advantage is the background-free correlation detection in noncollinear SHG geometry. Recently, with the appearance of femtosecond chirped-pulse regenerative amplifiers providing pulse energies well above 100 microjoule at 100-fs duration the TPEF may become again a competitive pulse duration measuring technique. At pulse intensities over 1-10 GW/cm² the two-photon-excited fluorescence can be strong enough for easy detection with a conventional CCD camera. In contrast to the second-harmonic generation, the TPEF has no restrictions on spatial wave matching and much less restrictions on wavelength tuning.

© 1996 Optical Society of America