Pulse capture without carrier absorption in dynamic Q photonic crystal nanocavities

We develop a gallium arsenide (GaAs) photonic crystal nanocavity device capable of capturing and releasing a pulse of light by dynamic control of the Q factor through free carrier photoexcitation. Unlike silicon-based devices where the performance of this dynamic optical control is limited by absorption from free carriers with nanosecond-order lifetimes, the short carrier lifetime (∼ 7 ps) of our equivalent GaAs devices enables dynamic control with negligible absorption losses. We capture a 4 ps optical pulse by briefly cycling the Q factor from 40,000 to 7900 and back just as the light couples to the nanocavity and confirm that the captured energy can be subsequently released on demand by a second injection of free carriers. Demonstrating dynamic control with negligible loss in a GaAs nanophotonic device also opens the door to dynamic control of cavity quantum electrodynamics with potential application towards quantum information processing.