Characterization of Femtosecond Light Pulses Coupled to Hollow-Pyramid Near-Field Probes: Localization in Space and Time

We perform the in situ characterization, by second-order optical autocorrelation, of femtosecond pulses transmitted by near-field optical probes. We demonstrate that transmission through hollow pyramid probes with diameter down to 65 nm has negligible effects on the duration of pulses as short as 30 fs. We also show that such probes allow obtaining, at their output, sufficient peak power to perform nonlinear optical experiments in the near field on such a space and time scale.