Investigation of Noise Processes in Nanophotonic Waveguides

Stimulated Brillouin Scattering (SBS) is a nonlinear process that results from the interaction between optical waves and acoustic vibrations in a transparent medium, and is driven by a number of physical processes including photoelasticity and electrostriction [1, 2].

Although the mechanisms and principles of operation for SBS are well-understood, there is still a lack in understanding of the noise processes that take place in nanophotonic waveguides. Earlier analyses such as that by Boyd et al. have shown that thermal fluctuations play a crucial role in the noise dynamics of SBS. More recent investigations by Rakich et al. [4, 5] have shown that noise mechanisms in SBS also play a crucial role in power transmission and signal stability in forward Brillouin interactions. The purpose of this research is to develop a general framework of noise dynamics in nanophotonic waveguides, by utilising techniques such as stochastic differential equation analysis and Fokker-Planck and Kolmogorov equations, to develop analytical and numerical models for the effective simulation of such dynamics. This framework will then be used as a standard procedure for computing the mean and variance of these processes, which will encapsulate all the important aspects of the noise and its influence in the Brillouin interactions. It is expected that these investigations will lead to a deeper understanding of the dynamical noise transfer between photons and phonons in waveguides, and to more accurate mathematical models for improving experimental design and analysis.

References:

[1] Wolff, C., Steel, M.J., Eggleton, B.J. and Poulton, C.G., 2015. Stimulated Brillouin scattering in integrated photonic waveguides: Forces, scattering mechanisms, and coupled-mode analysis. Physical Review A, 92(1), p.013836.

[2] Sipe, J.E. and Steel, M.J., 2016. A Hamiltonian treatment of stimulated Brillouin scattering in nanoscale integrated waveguides. New Journal of Physics, 18(4), p.045004.

[3] Boyd, R.W., Rza̧ewski, K. and Narum, P., 1990. Noise initiation of stimulated Brillouin scattering. Physical Review A, 42(9), p.5514.

[4] Kharel, P., Behunin, R.O., Renninger, W.H. and Rakich, P.T., 2016. Noise and dynamics in forward Brillouin interactions. Physical Review A, 93(6), p.063806.

[5] Behunin, R., Otterstrom, N.T., Rakich, P.T., Gundavarapu, S. and Blumenthal, D.J., 2018. Fundamental noise dynamics in cascaded-order Brillouin lasers. arXiv preprint arXiv:1802.03894.