Gigahertz-bandwidth optical memory in Pr3+:Y2SiO5

Abstract

We experimentally study a broadband implementation of the atomic frequency comb (AFC) rephasing protocol with a cryogenically cooled Pr3+:Y2SiO5 crystal. To allow for storage of broadband pulses, we explore a novel regime where the input photonic bandwidth closely matches the inhomogeneous broadening of the material (∼ 5 GHz), thereby significantly exceeding the hyperfine ground and excited state splitting (∼ 10MHz). Through an investigation of different AFC preparation parameters, we measure a maximum efficiency of 10% after a rephasing time of 12.5 ns. With a suboptimal AFC, we witness up to 12 rephased temporal modes.