The proper design of optical nanoscale devises, such as Fabry-Perot interferometers used for polariton construction, relies on scientists and engineers understanding the fundamental physical properties of metallic coatings. While properties such as the extinction coefficient, refractive index, and skin depth are well understood and have been modeled for many metals, acoustic phonon vibrations within metallic films at nanoscale thicknesses have only recently become a topic of discussion within the optical community. This is largely because the observance of acoustic phonon vibrations in thin films is relegated to having an impact on ultrafast transient spectroscopy, which has only become a major research tool over the past few decades. Through this manuscript the optical properties of aluminum thin films is discussed. It is determined that the period of the phonon vibration has a linear relationship to film thickness. A formalism relating phonon period to film thickness via the speed of sound is introduced, and it is shown to closely match with the well-stablished Debye equation used to model phonon vibrations.

中文翻译：

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纳米级铝涂层中的基本声学振动。


光学纳米级设计的正确设计，例如用于极化激元构建的法布里-珀罗干涉仪，依赖于科学家和工程师对金属涂层基本物理特性的了解。虽然消光系数、折射率和集肤深度等特性已经得到很好的理解，并且已经为许多金属建模，但纳米级厚度金属薄膜内的声子振动直到最近才成为光学界讨论的话题。这主要是因为对薄膜中声子振动的观察被降级为对超快瞬态光谱的影响，而超快瞬态光谱只是在过去几十年中才成为一种主要的研究工具。通过这份手稿，讨论了铝薄膜的光学特性。确定声子振动的周期与薄膜厚度呈线性关系。介绍了一种通过声速将声子周期与薄膜厚度联系起来的形式主义，并且表明它与用于模拟声子振动的成熟德拜方程非常吻合。