The quasi-light-storage (QLS) is a method for the variable and almost distortion free storage of optical data which is based on stimulated Brillouin scattering (SBS). The natural gain bandwidth of SBS limits the storage time of this method to up to 100 ns. We overcome this limit by the superposition of the SBS gain bandwidth with two losses. With this narrowed gain bandwidth, we were able to enhance the storage time for the QLS by 40%.
The quasi-light-storage (QLS) is a method for the variable and almost distortion free storage of optical data which is based on stimulated Brillouin scattering (SBS). The natural gain bandwidth of SBS limits the storage time of this method to up to 100 ns. We overcome this limit by the superposition of the SBS gain bandwidth with two losses. With this narrowed gain bandwidth, we were able to enhance the storage time for the QLS by 40%.
The core elements of optical packet-switched networks rely on optical routers. A key technology for the realization of such components is the variable delay and storage of optical data packets. Optical Memories are used for tasks, such as packet buffering for collision avoidance and synchronization, as well as processing of headers in optical routers. The quasi-light storage (QLS) is a method for the variable and almost distortion free optical data storage, which can be realized within the entire transparency range of optical fibers with standard telecommunication components. QLS is based on the time-frequency-coherence and utilizes stimulated Brillouin scattering (SBS) for filtering the spectrum of the data signal. Due to the natural bandwidth of the SBS, the maximum storage time of the QLS is limited to 100 ns. By reducing the bandwidth, the storage time can be significantly increased. There exist some approaches for reducing the SBS bandwidth. Firstly, the Brillouin gain can be superimposed with two losses and secondly, an aperture in the frequency range can be used. Both methods achieve a SBS bandwidth of about 3 MHz, but have some disadvantages when applied to the QLS. For the superposition method, the overall gain is too low, and for the other method the aperture cannot be separated from the signal. In this paper we show the reduction of the Brillouin gain bandwidth through a feedback system. The sampled signal passes several times through the system, so that the Brillouin gain bandwidth is reduced. This leads to a drastic increase of the QLS storage time. In a first experiment with single pulses, a maximum storage time of 600 ns was achieved, which corresponds to a sixfold increase compared to a normal system QLS.
We investigate the gain bandwidth of stimulated Brillouin scattering (SBS) in multistage systems. As we will show, the bandwidth is reduced significantly by the number of stages, which can increase the distortions in cascaded slow-light systems, for instance. However, other applications, which are limited by the minimum bandwidth achievable with SBS, can benefit from the reduced bandwidth. Since the peak value of the SBS gain spectrum is not reduced by this method, the reduced bandwidth can drastically enhance the performance of many different applications, such as the quasi-light storage (QLS). The minimum bandwidth of 10.3 MHz for a one-stage system was reduced down to 5.8 MHz for three stages. With this reduced bandwidth, we achieved a storage time advancement of the QLS method by 60%.
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.
The manipulation of the group velocity of optical signals (slow and fast light) has many possible applications in telecommunications, sensing, nonlinear optics, and so on. The exploitation of the effect of stimulated Brillouin scattering (SBS) is of special interest for the alteration of the group velocity in optical fibers, since it just requires standard telecom equipment and low-to-moderate optical power. However, each delay in one single, low-gain SBS-based slow-light system is accompanied by a pulse broadening. This is a result of the inherent Kramers–Kronig relations among the gain, the phase change, and the accompanied group velocity. For an ideal flat gain, the phase change is nonideal, and for an ideal phase change the gain curve leads to a broadening. Furthermore, if the gain bandwidth is adapted to the signal by broadening, the delay will be reduced. Thus the signal broadening can be reduced by several methods for one single low-gain slow-light system, but it cannot be zero. Here, we will show how a zero-broadening SBS-based slow light can be achieved with several methods. The basic idea is a reshaping of the original pulse in a second stage by saturation of the SBS system, or by the superposition of two gains. As will be shown, all of these systems show an almost ideal overall gain and phase function over the bandwidth of the pulses. Thus, SBS-based slow light with a delay bandwidth product of 1 bit and zero distortion is possible.
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.