100-FEMTOSECOND 100-NANOMETER NEAR-FIELD PROBE

Cross-correlation by upconversion has been used to measure pulse width s below 100 fs emitted from an aluminum-coated fiber near-field tip of the variety reported by Betzig et al. [Science 251 (1991) 1468]. The pulses are 0.8 mu m center-wavelength with 76 MHz repetition rate gene rated by a Ti:sapphire mode-locked laser. The size of the probe is est imated at 100 nm by SEM micrographs and previous experience with simil ar probes used in our continuous wave NSOM systems. We measure average tip output powers of similar to 1 nW for average input powers of simi lar to 500 mu W.