Dynamical ultrafast all-optical switching of planar GaAs/AlAs photonic microcavities

TL;DR

This paper demonstrates ultrafast all-optical switching in GaAs/AlAs microcavities, achieving rapid resonance shifts through free carrier excitation, with potential for tenfold speed improvements via sample optimization.

Contribution

The study introduces a method for ultrafast optical switching of microcavities using free carrier excitation and provides insights into the dynamic behavior of the refractive index changes.

Findings

Achieved up to 0.8% refractive index change

Resonance shifted by 3.3 linewidths within a few picoseconds

Switching-off decay time around 50 ps

Abstract

The authors study the ultrafast switching-on and -off of planar GaAs/AlAs microcavities. Up to 0.8% refractive index changes are achieved by optically exciting free carriers at 1720 nm and a pulse energy of 1.8 micro Joules. The cavity resonance is dynamically tracked by measuring reflectivity versus time delay with tunable laser pulses, and is found to shift by as much as 3.3 linewidths within a few picoseconds. The switching-off occurs with a decay time of around 50 ps. The authors derive the dynamic behavior of the carrier density and of the complex refractive index. They propose that the inferred 10 GHz switching rate may be tenfold improved by optimized sample growth.