We describe the generation of second harmonic light (525 nm) from femtosecond near-infrared (NIR, 1050 nm) pulses from three nanoparticle films: gold nanospheres, hexagonal nanodisks of covellite (CuS), and a bilayer comprising covellite and gold films. Enhanced second-harmonic generation (SHG), fourth order in the NIR pump intensity, arises from coupling of plasmon resonance modes of CuS and Au. Above 6 GW/cm2, the enhanced SHG from the bilayer film is much larger than the incoherent sum of SHG from the Au and CuS films separately, and the SHG efficiency of the bilayer (Au:CuS) films is nine times larger than that of BBO per unit thickness.
A key challenge to widespread implementation of silicon photonics is achieving optical switching at ultrafast speed and ultralow power using on-chip silicon modulators. Here we report experiments demonstrating that the ultrafast photo-induced phase transition in VO2 can be harnessed for all-optical in the telecommunications band when small VO2 volumes are integrated within a silicon waveguide. "On"-to-"off" switching speeds in this in-line modulator are less than 1 ps, thus consistent with Tbps speeds, and switching energies near threshold are less than 500 fJ for modulation depths near 6 dB. Early results showing significant reductions in switching energies in hybrid VO2:Si ring resonators will also be presented.
All-optical modulators are likely to play an important role in future chip-scale information processing systems. In this
work, through simulations, we investigate the potential of a recently reported vanadium dioxide (VO2) embedded silicon
waveguide structure for ultrafast all-optical signal modulation. With a VO2 length of only 200 nm, finite-differencetime-
domain simulations suggest broadband (200 nm) operation with a modulation greater than 12 dB and an insertion
loss of less than 3 dB. Predicted performance metrics, including modulation speed, modulation depth, optical bandwidth,
insertion loss, device footprint, and energy consumption of the proposed Si-VO2 all-optical modulator are benchmarked
against those of current state-of-the-art all-optical modulators with in-plane optical excitation.