Temporal Dynamics of On-Chip Quasi-Light Storage

Storing and delaying optical signals is key for signal processing and control in many microwave photonics, quantum and classical communication systems. Hence, scientists proposed and demonstrated a multitude of approaches, from slow-light in photonic crystals, ring resonators, to optomechanical and stimulated Brillouin scattering (SBS) based schemes [1]. Yet, a scheme that offers tunable, long delays in a small form factor is still elusive. Quasi-light storage (QLS) is an optical pulse storage method that has been used to achieve long, dynamically adjustable delay times in optical fibres by utilising SBS to spectrally sample a signal with an optical frequency comb [2]. Relying on long lengths of fibre, however, limits Size, Weight, and Power consumption (SWaP) and induces latency much larger than the storage time. Here, we demonstrate QLS on a photonic chip and achieve delay times an order of magnitude larger than the optical chip transit time. We experimentally show that the SBS interaction between the signal and the pump on the chip creates a single acoustic wave that stores the optical pulse information, and we investigate the temporal dynamics of this storage mechanism. We demonstrate that the repeated interaction of the acoustic wave and optical pump pulses reinforces the acoustic wave, and storage times an order of magnitude larger than the intrinsic acoustic lifetime can be achieved.