TY - GEN A1 - Gutsche, Philipp A1 - Wolff, Christian A1 - Mirnaziry, Sayyed R. A1 - Poulton, Christopher G. T1 - Coupled-Mode Equations for Stimulated Brillouin Scattering T2 - CUDOS 14th Annual Workshop 2015 Handbook N2 - Stimulated Brillouin Scattering (SBS) is a third-order nonlinear optical effect which originates from the interplay of acoustics and optics. Recently, SBS has been harnessed in nano-photonic waveguides for applications such as narrow-linewidth lasers and Brillouin dynamic gratings [1]. Since the timescales of both phenomena differ significantly, coupled-mode equations derived from a slowly varying envelope approximation are well suited for numerical investigations of SBS [2]. We use the Relaxation Method (RM) [3] to study the optical power transfer and spatially resolved power distributions in long waveguides in the steady state limit. Y1 - 2015 ER - TY - JOUR A1 - Wolff, Christian A1 - Gutsche, Philipp A1 - Steel, Michael J. A1 - Eggleton, Benjamin J. A1 - Poulton, Christopher G. T1 - Power limits and a figure of merit for stimulated Brillouin scattering in the presence of third and fifth order loss JF - Opt. Express N2 - We derive a set of design guidelines and a figure of merit to aid the engineering process of on-chip waveguides for strong Stimulated Brillouin Scattering (SBS). To this end, we examine the impact of several types of loss on the total amplification of the Stokes wave that can be achieved via SBS. We account for linear loss and nonlinear loss of third order (two-photon absorption, 2PA) and fifth order, most notably 2PA-induced free carrier absorption (FCA). From this, we derive an upper bound for the output power of continuous-wave Brillouin-lasers and show that the optimal operating conditions and maximal realisable Stokes amplification of any given waveguide structure are determined by a dimensionless parameter ℱ involving the SBS-gain and all loss parameters. We provide simple expressions for optimal pump power, waveguide length and realisable amplification and demonstrate their utility in two example systems. Notably, we find that 2PA-induced FCA is a serious limitation to SBS in silicon and germanium for wavelengths shorter than 2200nm and 3600nm, respectively. In contrast, three-photon absorption is of no practical significance. Y1 - 2015 U6 - https://doi.org/10.1364/OE.23.026628 VL - 23 IS - 20 SP - 26628 EP - 26638 ER - TY - JOUR A1 - Wolff, Christian A1 - Gutsche, Philipp A1 - Steel, Michael J. A1 - Eggleton, Benjamin J. A1 - Poulton, Christopher G. T1 - Impact of nonlinear loss on stimulated Brillouin scattering JF - J. Opt. Soc. Am. B N2 - We study the impact of two-photon absorption (2PA) and fifth-order nonlinear loss such as 2PA-induced free-carrier absorption in semiconductors on the performance of stimulated Brillouin scattering devices. We formulate the equations of motion including effective loss coefficients, whose explicit expressions are provided for numerical evaluation in any waveguide geometry. We find that 2PA results in a monotonic, algebraic relationship between amplification, waveguide length, and pump power, whereas fifth-order losses lead to a nonmonotonic relationship. We define a figure of merit for materials and waveguide designs in the presence of fifth-order losses. From this, we determine the optimal waveguide length for the case of 2PA alone and upper bounds for the total Stokes amplification for the case of 2PA as well as fifth-order losses. The analysis is performed analytically using a small-signal approximation and is compared to numerical solutions of the full nonlinear modal equations. Y1 - 2015 U6 - https://doi.org/10.1364/JOSAB.32.001968 VL - 32 IS - 9 SP - 1968 EP - 1978 ER -