标题： 布里渊共振展宽由于纳米尺度波导中的结构变化 显示英文标题

标题： Brillouin resonance broadening due to structural variations in nanoscale waveguides

摘要： 我们研究了结构变化（即缓慢变化的几何像差和内部应变场）对纳米尺度波导中受激布里渊散射（SBS）共振宽度和形状的影响。 我们发现，它们通过两种不同的机制导致共振的均匀展宽：首先，声学频率通过机械非线性直接受到影响；其次，光学波数通过光-机非线性受到影响，从而通过相位匹配条件导致额外的声学频率偏移。 我们发现，这种第二种机制与光-机耦合成正比，因此与SBS增益本身相关。 在同模前向SBS中，这种机制不存在，而在反向散射中则起着重要作用。 在反向SBS中，超过由制造公差定义的阈值后，增加光-声重叠将不再产生预期的总体斯托克斯放大的二次增长。 最后，我们通过一个数值例子说明，在反向SBS和跨模前向SBS中，两种符号相反的展宽机制的存在也开辟了补偿几何引起的展宽的可能性。 我们的结果可以推广到其他微米和纳米结构波导几何结构，如光子晶体光纤。 显示英文摘要

摘要： We study the impact of structural variations (that is slowly varying geometry aberrations and internal strain fields) on the width and shape of the stimulated Brillouin scattering (SBS) resonance in nanoscale waveguides. We find that they lead to an homogeneous resonance broadening through two distinct mechanisms: firstly, the acoustic frequency is directly influenced via mechanical nonlinearities; secondly, the optical wave numbers are influenced via the opto-mechanical nonlinearity leading to an additional acoustic frequency shift via the phase-matching condition. We find that this second mechanism is proportional to the opto-mechanical coupling and, hence, related to the SBS-gain itself. It is absent in intra-mode forward SBS, while it plays a significant role in backward scattering. In backward SBS increasing the opto-acoustic overlap beyond a threshold defined by the fabrication tolerances will therefore no longer yield the expected quadratic increase in overall Stokes amplification. Finally, we illustrate in a numerical example that in backward SBS and inter-mode forward SBS the existence of two broadening mechanisms with opposite sign also opens the possibility to compensate the effect of geometry-induced broadening. Our results can be transferred to other micro- and nano-structured waveguide geometries such as photonic crystal fibres.