Observation of strongly enhanced ultrashort pulses in 3-D metallic funnel-waveguide

Abstract

For strong field enhancement of ultrashort light pulses, a 3-D metallic funnel-waveguide is analyzed using the finite-difference time-domain (FDTD) method. Then the maximum intensity enhancement actually developed by the funnel-waveguide upon the injection of femtosecond laser pulses is observed using two-photon luminescence (TPL) microscopy. In addition, the ultrafast dephasing profile of the localized field at the hot spot of the funnel-waveguide is verified through the interferometric autocorrelation of the TPL signal. Finally it is concluded the funnel-waveguide is an effective 3-D nanostructure that is capable of boosting the peak pulse intensity of stronger than 80 TWcm(-2) by an enhancement factor of 20 dB without significant degradation of the ultrafast spatiotemporal characteristics of the original pulses.

Spectral Difference Interferometry for the Characterization of Optical Media

“…Our proposed scheme requires only minimal numerical processing to extract the desired parameters, in contrast to fringe‐based white light or sweeping arm interferometry, but does, however, require four optical power measurements to generate one measurement of the relative phase between the two tones. The fast swept laser approach aims to overcome environmental error by performing a measurement over time scales faster than fluctuations in the environment.…”

“…This is usually achieved by maintaining the paths of both the probe and reference arms at similar lengths and isolating the system from mechanical vibrations to the greatest extent possible. The former places practical limitations upon the maximum length of device which can be measured using such schemes, whilst the latter complicates implementation and presents challenges in harsh environments. Sagnac‐interferometers largely bypass such coherency challenges; provided that the transit time of the light is short compared to the time period of mechanical vibrations to which the interferometer is subject, light travelling in both directions will essentially pass through the medium in the same state and hence see the same optical path length.…”