Electric-dipole absorption resonating with longitudinal optical phonon-plasmon system and its effect on dispersion relations of interface phonon polariton modes in metal/semiconductor-stripe structures
Electric-dipole absorption resonating with longitudinal optical phonon-plasmon system and its effect on dispersion relations of interface phonon polariton modes in metal/semiconductor-stripe structures
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DOI：
10.1088/1361-6463/aa9918
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发表时间：
2018-01
期刊：
影响因子：
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通讯作者：
Hironori Sakamoto;Eito Takeuchi;Kouki Yoshida;K. Morita;B. Ma;Y. Ishitani
中科院分区：
文献类型：
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作者：
Hironori Sakamoto;Eito Takeuchi;Kouki Yoshida;K. Morita;B. Ma;Y. Ishitani
界面声子极化激元（IPhPs）在纳米结构中不包括金属成分，因为它们具有较低的光发射或吸收损耗和较高的品质因子比表面等离子体激元。在以往的研究中，发现强红外吸收是基于p偏振光与材料的相互作用，共振光子能量高度依赖于结构尺寸和入射角。我们报告的光吸收的金属/半导体（体GaAs和薄膜AlN）的条纹结构在太赫兹到中红外区域的电场的光垂直于条纹，其中s-和p-偏振光被吸收。吸收与纵向光学（LO）声子或LO声子-等离子体激元耦合（LOPC）模式共振，因此与入射角或结构尺寸无关。这种吸收归因于在金属/半导体、异质界面或高电子密度层和凹陷层的界面处的光致极化电荷的电偶极子。介电常数通过这些偶极子的形成而改变。利用我们的改变的介电常数的形式来解释这些样品中的金属/半导体-IPhP和SPhP的实验色散关系是必不可少的。分析表明，SiC衬底上的金属/AlN膜条形结构中的IPhPs高度局限于AlN膜中，而金属/体GaAs结构的介电常数部分受电偶极子的影响。未掺杂样品的电偶极吸收品质因子为42-54，Al/AlN-IPhP样品的电偶极吸收品质因子为62。认为含金属的结构对半导体声子能区的模能选择性并不构成障碍。
Interface phonon polaritons (IPhPs) in nano-structures excluding metal components are thoroughly investigated because they have lower loss in optical emission or absorption and higher quality factors than surface plasmon polaritons. In previous reports, it is found that strong infrared (IR) absorption is based on the interaction of p-polarized light and materials, and the resonance photon energy highly depends on the structure size and angle of incidence. We report the optical absorption by metal/semiconductor (bulk-GaAs and thin film-AlN)-stripe structures in THz to mid-IR region for the electric field of light perpendicular to the stripes, where both of s- and p-polarized light are absorbed. The absorption resonates with longitudinal optical (LO) phonon or LO phonon-plasmon coupling (LOPC) modes, and thus is independent of the angle of incidence or structure size. This absorption is attributed to the electric dipoles by the optically induced polarization charges at the metal/semiconductor, heterointerfaces, or interfaces of high electron density layers and depression ones. The electric permittivity is modified by the formation of these dipoles. It is found to be indispensable to utilize our form of altered permittivity to explain the experimental dispersion relations of metal/semiconductor-IPhP and SPhP in these samples. This analysis reveals that the IPhPs in the stripe structures of metal/AlN-film on a SiC substrate are highly confined in the AlN film, while the permittivity of the structures of metal/bulk-GaAs is partially affected by the electric-dipoles. The quality factors of the electric-dipole absorption are found to be 42–54 for undoped samples, and the value of 62 is obtained for Al/AlN-IPhP. It is thought that metal-contained structures are not obstacles to mode energy selectivity in phonon energy region of semiconductors.