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arXiv 1506.01720physics.optics
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表面受限共振受激布里渊散射中的巨增益增强

Giant Gain Enhancement in Surface-Confined Resonant Stimulated Brillouin Scattering

Nathan Dostart, Seunghwi Kim, Gaurav Bahl

摘要:

受激布里渊散射(SBS)主要由体材料性质定义的概念已被最近对纳米波导的研究所推翻。现在可以理解,在这种高度受限的波导中出现的辐射压力和电致伸缩的边界力可以对布里渊增益做出显著贡献。在这里,这个概念被扩展到显示,增益增强不需要纳米级或亚波长的功能,但通常出现在光场和声场同时限制在自由表面或材料界面附近。这种情况经常发生在回音壁谐振器(WGR)中,使得增益增强比以前认为的更容易实现。为了说明这一概念,第一个全矢量的分析模型SBS在WGR的开发,包括光学边界力,和SBS增益在常见的二氧化硅WGR的几何形状计算评估。这些结果预测,增益$10^4$倍以上的标量理论的预测可能会出现在WGR,甚至在100微米的尺寸范围。此外,梯形横截面微盘可以表现出非常大的SBS增益,接近$10^2$ m $^{-1}$ W $^{-1}$。在包括谐振放大的情况下,可以实现数量级为$10^{12}$ m $^{-1}$ W $^{-1}$的极端增益,其比线性波导系统中的最高预测增益大$10^8$倍。

英文摘要:

The notion that Stimulated Brillouin Scattering (SBS) is primarily defined by bulk material properties has been overturned by recent work on nanoscale waveguides. It is now understood that boundary forces of radiation pressure and electrostriction appearing in such highly confined waveguides can make a significant contribution to the Brillouin gain. Here, this concept is extended to show that gain enhancement does not require nanoscale or subwavelength features, but generally appears where optical and acoustic fields are simultaneously confined near a free surface or material interface. This situation routinely occurs in whispering gallery resonators (WGRs), making gain enhancements much more accessible than previously thought. To illustrate this concept, the first full-vectorial analytic model for SBS in WGRs is developed, including optical boundary forces, and the SBS gain in common silica WGR geometries is computationally evaluated. These results predict that gains $10^4$ times greater than the predictions of scalar theory may appear in WGRs even in the 100 um size range. Further, trapezoidal cross-section microdisks can exhibit very large SBS gains approaching $10^2$ m$^{-1}$W$^{-1}$. With resonant amplification included, extreme gains on the order of $10^{12}$ m$^{-1}$W$^{-1}$ may be realized, which is $10^8$ times greater than the highest predicted gains in linear waveguide systems.

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