Spatio-temporal ultrafast pulse shaping at the femtosecond-nanometer scale.

Optical pulse shaping is a fundamental tool for coherent control of the light-matter interaction. While such control enables the measurement of ultrafast temporal dynamics, simultaneous spatiotemporal control is required for studying non-local ultrafast charge dynamics at the nanoscale. However, obtaining accurate spatial control at a sub-wavelength resolution with conventional optical elements poses significant difficulty.

Adiabatic four-wave mixing frequency conversion.

We introduce the concept of adiabatic four-wave mixing (AFMW) frequency conversion in cubic nonlinear media through an analogy to dynamics in quantum two-level systems. Rapid adiabatic passage in four-wave mixing enables coherent near-100% photon number down-conversion or up-conversion over a bandwidth much larger than ordinary phase-matching bandwidths, overcoming the normal efficiency-bandwidth trade-off. We develop numerical methods to simulate AFWM pulse propagation in silicon photonics and fiber platforms as examples.

Pulse shaping of broadband adiabatic SHG from a Ti-sapphire oscillator.

We experimentally demonstrate an efficient broadband second-harmonic generation (SHG) process with a tunable mode-locked Ti:sapphire oscillator. We have achieved a robust broadband and efficient flat conversion of more than 35 nm wavelength by designing an adiabatic aperiodically poled potassium titanyl phosphate crystal. Moreover, we have shown that with such efficient flat conversion, we can shape and control broadband second-harmonic pulses.