Noise Dynamics in Stimulated Brillouin Scattering
Interactions between light and sound in optical waveguides are of great interest in the photonics and quantum computation communities, due to the potential for information storage and transmission via acoustic and optical pulses. Such interactions are made possible via nonlinear optical processes su...
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| Format: | Dissertation |
| Language: | English |
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ProQuest Dissertations & Theses
01-01-2022
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| Online Access: | Get full text |
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| Summary: | Interactions between light and sound in optical waveguides are of great interest in the photonics and quantum computation communities, due to the potential for information storage and transmission via acoustic and optical pulses. Such interactions are made possible via nonlinear optical processes such as Raman scattering and stimulated Brillouin scattering (SBS). SBS has been used in the past three decades for multiple applications, including optical and acoustic sensing, novel microscopy and endoscopy applications, microwave and optical filtering, and more recently information storage via acoustic waves. However, noise arising from the thermal acoustic background has been shown to also be amplified by the SBS process. Although previous studies have investigated the noise properties of the SBS process in the steady-state regime, our understanding of these processes is still limited. This research intends to fill this gap by developing new mathematical and numerical models that capture these noise dynamics in more detail, and how they impact applications such as opto-acoustic storage. In this Thesis, we extend the theoretical analysis of SBS to short pulses by deriving a set of coupled SBS equations with thermal and laser noise, and investigate the noise properties within the undepleted pump regime. We show that in the case of a constant energy pump field and lossy media, the optical signal-to-noise ratio (OSNR) has a minimum in the region where the interaction time of the pulses matches their transit time in the waveguide. Then, we develop a numerical method for solving the coupled stochastic partial differential equations beyond the undepleted pump approximation. We find that the noise properties of the fields rely on the length of the optical pulses involved as well as on the net SBS gain in the waveguide. Furthermore, for short-pump, low gain regimes, the spontaneous Stokes field is found to be incoherently amplified, thus exhibiting large spatial and temporal fluctuations, whereas for the long-pump, high gain regime the field is amplified coherently, resulting in a smooth field but with large variations in peak power between independent realizations. Similar observations were made for the stimulated scattering case using a Stokes seed. Finally, we perform numerical simulations of Brillouin storage under different modulation schemes, namely amplitude storage and phase storage, and find that phase storage offers longer storage times as a result of phase encoding being more robust to noise than amplitude encoding, in accordance with the additive-white-Gaussian-noise (AWGN) model of discrete communication theory. |
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| ISBN: | 9798383408001 |