Birgit Stiller, Kevin Jaksch, Johannes Piotrowski, Moritz Merklein, Mikołaj K. Schmidt, Khu T. Vu, Pan Ma, Steve Madden, Michael J. Steel, Christopher G. Poulton, Benjamin J. Eggleton
Abstract Signal processing based on stimulated Brillouin scattering (SBS) is limited by the narrow linewidth of the optoacoustic response, which confines many Brillouin applications to continuous wave signals or optical pulses longer than several nanoseconds. In this work, we experimentally demonstrate Brillouin interactions at the 150 ps time scale and a delay for a record 15 ns which corresponds to a delay of 100 pulse widths. This breakthrough experimental result was enabled by the high local gain of the chalcogenide waveguides as the optoacoustic interaction length reduces with pulse width. We successfully transfer 150ps-long pulses to traveling acoustic waves within a Brillouin-based memory setup. The information encoded in the optical pulses is stored for 15 ns in the acoustic field. We show the retrieval of eight amplitude levels, multiple consecutive pulses and low distortion in pulse shape. The extension of Brillouin-based storage to the ultra-short pulse regime is an important step for the realisation of practical Brillouin-based delay lines and other optical processing applications.
Abstract Signal processing based on stimulated Brillouin scattering (SBS) is limited by the narrow linewidth of the optoacoustic response, which confines many Brillouin applications to continuous wave signals or optical pulses longer than several nanoseconds. In this work, we experimentally demonstrate Brillouin interactions at the 150 ps time scale and a delay for a record 15 ns which corresponds to a delay of 100 pulse widths. This breakthrough experimental result was enabled by the high local gain of the chalcogenide waveguides as the optoacoustic interaction length reduces with pulse width. We successfully transfer 150ps-long pulses to traveling acoustic waves within a Brillouin-based memory setup. The information encoded in the optical pulses is stored for 15 ns in the acoustic field. We show the retrieval of eight amplitude levels, multiple consecutive pulses and low distortion in pulse shape. The extension of Brillouin-based storage to the ultra-short pulse regime is an important step for the realisation of practical Brillouin-based delay lines and other optical processing applications.
Signal processing based on stimulated Brillouin scattering (SBS) is limited by the narrow linewidth of the optoacoustic response, which confines many Brillouin applications to continuous wave signals or optical pulses longer than several nanoseconds. In this work, we experimentally demonstrate Brillouin interactions at the 150 ps time scale and a delay for a record 15 ns which corresponds to a delay of 100 pulse widths. This breakthrough experimental result was enabled by the high local gain of the chalcogenide waveguides as the optoacoustic interaction length reduces with pulse width. We successfully transfer 150ps-long pulses to traveling acoustic waves within a Brillouin-based memory setup. The information encoded in the optical pulses is stored for 15 ns in the acoustic field. We show the retrieval of eight amplitude levels, multiple consecutive pulses and low distortion in pulse shape. The extension of Brillouin-based storage to the ultra-short pulse regime is an important step for the realisation of practical Brillouin-based delay lines and other optical processing applications.
Efficient and extended light storage mechanisms are pivotal in photonics, particularly in optical communications, microwave photonics, and quantum networks, as they offer a direct route to circumvent electrical conversion losses and surmount bandwidth constraints. Stimulated Brillouin Scattering (SBS) is an established method to store optical information by transferring it to the acoustic domain, but current on-chip SBS efforts have limited bandwidth or storage time due to the phonon lifetime of several nanoseconds. An alternate approach known as quasi-light storage (QLS), which involves the creation of delayed replicas of optical data pulses via SBS in conjunction with a frequency comb, has been proposed to lift the storage time constraint; however, its realization has been confined to lengthy optical fibers, constraining integration with on-chip optical elements and form factors. Here, we present an experimental demonstration of QLS on a photonic chip leveraging the large SBS gain of chalcogenide glass, achieving delays of up to 500 ns for 1 ns long signal pulses, surpassing typical Brillouin storage processes' acoustic lifetime by more than an order of magnitude and waveguide transit time by two orders of magnitude. We experimentally and numerically investigate the dynamics of on-chip QLS and reveal that the interplay between the acoustic wave that stores the optical signal and subsequent optical pump pulses leads to a reshaping of the acoustic field. Our demonstrations illustrate the potential for achieving ultra-long storage times of individual pulses by several hundred pulse widths, marking a significant stride toward advancing the field of all-optical storage and delay mechanisms.
Abstract Storing or delaying optical signals is of key interest for fundamental research and applications in radar, microwave signal processing, quantum information as well as optical communication systems. Delay systems based on stimulated Brillouin scattering (SBS), a coherent interaction between optical and acoustic waves can be implemented in optical fiber or chip-scale platforms, operate at room temperature and can be fully controlled via the optical pump wave. In this article, we review delay and storage techniques based on SBS. We present SBS slow-light, fiber delay lines based on Brillouin dynamic gratings, Brillouin quasi-light storage and Brillouin-based light storage via photon-phonon conversion and compare their performance. In this process, we also include an overview of different platforms used for Brillouin light storage and delay schemes, such as optical fiber, planar soft-glass waveguides, and silica fiber-tip resonators.
Optical and acoustic waves can interact over the nonlinear effect of stimulated Brillouin scattering (SBS), which is a coherent process. By using traveling acoustic waves, we recently showed proof-of-principle experiments of Brillouin-based light storage. The particularity of Brillouin-based light storage is the strict phase-matching condition. This allows for different features: simultaneous storage at multiple wavelengths, cascaded storage at different spatial positions, and nonreciprocal storage with a GHz bandwidth. However, the delay time of this technique has so far been limited to the acoustic lifetime of about 10 ns. In this talk, I will discuss our recent results on coherent photon-phonon interaction. One focus will be on a proof-of-principle experiments on how to reinforce acoustic phonons. This enables us to overcome the obstacle of the limited acoustic lifetime by optically reinforcing the acoustic wave.
Storing and delaying optical information is of crucial importance for optical communications, signal processing and in the quantum domain. A plethora of techniques for optical storage have been shown which aim to maintain as much as possible the advantages of optics, such as e.g. the coherence, the bandwidth and capacity. In particular the interaction of optical waves with mechanical motion offers a solution to buffer optical information [1-4]. It was shown that one can use acoustic waves to store and delay optical signals coherently via the effect of stimulated Brillouin scattering (SBS) [3,4]. This allows for simultaneous storage at multiple wavelengths [5], cascaded storage at different spatial positions [6], and nonreciprocal storage with a GHz bandwidth [7]. However, the delay time of this technique is so far limited to the acoustic lifetime of about 10 ns.
The importance of optical signal processing techniques is growing rapidly in recent years due to the exponentially increasing demand for bandwidth, capacity and power efficiency in communications and computing. However, due to their bosonic nature photons do not interact with each other, unless there is a nonlinear medium mediating the interaction. One of the strongest nonlinear effects is the interaction of light waves, photons, with sound-waves, acoustic phonons, which is known as stimulated Brillouin scattering (SBS). This thesis experimentally investigates SBS in photonic chips. It is shown in this thesis that the fundamental interaction strength between light and sound waves can be tailored by using one-dimensional photonic bandgap structures, completely suppressing the effect or alternatively enhancing the interaction to form phase-locked Brillouin frequency combs. It was shown furthermore that efficiently generating SBS on-chip enables the generation of stable RF signals that are widely tunable in frequency. Finally, it is shown in this thesis that SBS enables the storage of light signals on a chip, one of the holy grails of all-optical signal processing. Delaying optical signals is of key importance in optical networks to enable synchronization, buffering, and rerouting. SBS enables large delays by resonantly transferring an optical signal to an acoustic wave, that travels five orders of magnitude slower and retrieving it after a certain storage time. It is demonstrated in this thesis that a Brillouin-based memory (BBM) technique allows storing amplitude and phase of optical data pulses and operate at multiple wavelengths with minimal cross-talk. Replenishing of the acoustic wave to overcome storage time limitations imposed by the lifetime of the acoustic wave as well as non-reciprocal light storage is also shown.