Short-pulse Opto-acoustic Storage

Abstract:
Using the principle of storing optical information in acoustic waves, we experimentally study the storage of pulses down to 150 ps whose bandwidth lies well beyond the Brillouin linewidth. A time-delay of 100 pulse-widths is achieved.

All-optical storage concepts for light that preserve coherence and bandwidth of optical signals have attracted much attention, as they are a highly desired goal for communication networks. Ideally, a possible solution works at room temperature and is compatible with state-of-the-art networks. Stimulated Brillouin scattering (SBS) can be harnessed for storing optical data in acoustic waves [1] enabling coherent storage in amplitude and phase and a broad bandwidth in planar waveguides without the need of a resonant structure [2].

In this work, we aim at extending the bandwidth and delay-bandwidth product of opto-acoustic storage. We demonstrate experimentally the storage of optical pulses with different pulse-width down to 150 ps. We study the retrieval of the pulse linewidth, pulse shape and amplitude states encoded on the signal.

The concept of opto-acoustic light storage is based on the effect of SBS and allows for the transfer of information from optical pulses to traveling acoustic phonons that propagate at a five orders of magnitude lower speed [1,2]. External control light pulses define position and storage time and allow for the deliberate control of the flow of the information, allowing for even cascading this process [3].

SBS-induced slow-light drew a lot of attention as it fulfills the requirements of being a coherent, broad-bandwidth storage concept at room temperature. However, they face challenges to achieve longer delays and were mostly limited to a delay of one or two pulse widths [4]. Here, we demonstrate the storage of an optical pulse for 100 pulse widths using the Brillouin-based memory (Fig. 1a). The giant Brillouin gain of the highly nonlinear waveguides enables the storage of short pulses with a pulse width of 150 ps for up to 15 ns (Fig. 1a). The bandwidth of the pulses exceeds the Brillouin linewidth by two orders of magnitude. We also show the retrieval of non-Gaussian pulse shapes, conserving their bandwidth (Fig. 1b) and study the decay of the retrieved data pulse depending on the pulse width (e.g. for a 280ps-long pulse in Fig. 1c).

Fig. 1. Experimental results: a) Storage of a 150ps-long data pulse for up to 15 ns; inset: undepleted and retrieved data after 2 ns. b) Retrieval of a double pulse with different amplitude difference. c) Decay of retrieved data of a 280ps-long pulse.

References:

[1] Z. Zhu, et al., Science 318, 1748–50 (2007).
[2] M. Merklein, et al., Nature Communications 8, 574 (2017).
[3] B. Stiller, et al., Optics Letters, 43 (18), 4321-4324 (2018).
[4] L. Thévenaz, Nature Photonics 8, 474-481 (2008).