表面電漿共振影響下的鋁奈米薄膜同調聲學振動

Generation and Detection of Coherent Acoustic Vibration in Aluminum Thin Film using Surface Plasmon Resonance Approach

顧坤挪(Kunal Kumar)

指導教授 ： 孫啟光

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202100890

摘要

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關鍵字

表面電漿 ； 鋁奈米薄膜 ； 聲學振動

並列摘要

Recently SPPs has attracted many attentions. Since the resonant frequency of SPPs highly depends on the medium’s dielectric constant, SPPs are very sensitive to the surrounding environment. SPR based techniques are very surface sensitive and detect little changes in the refractive index and changes in a layer thickness of 1 nm and much less to be detected. In this study, a time-resolved pump-probe reflection method is integrated with a surface plasmon resonance (SPR) technique in Kretschmann configuration for exploring the ultrafast light-induced processes in a thin Aluminum metal film. Acoustic vibrations are generated in the Aluminum film on a prism. They are detected in the time domain through reflectivity modulation for probe pulses that satisfy the Surface Plasmon Resonance condition. We propose and demonstrate Aluminum’s (Al) films high potential as plasmonics material and its advantages over other noble metals. Basic understanding for the optical excitation of surface plasmon and prism coupling using the total internal reflection is discussed. The generation and detection of acoustic vibration in Al thin film is done by using the SPR approach, combining the Kretschmann geometry configuration with the time-resolved femtosecond pump-probe experiment. In 20 nm sample, we observe an interesting result in terms of time delay, when light incident angle is close to surface resonance angle the time delay is very small it is because of different sensing region of probe light. So it’s all about two probing mechanism and the dominating behavior. Clear acoustic oscillations are observed in our experimental results. Our fitting model shows that the lattice expansion accompany with fast heating of the lattice (due to anharmonicity of the lattice potential) contribute to the generation of acoustic vibration in Al film resulting in cosine like oscillation.

並列關鍵字

Generation ； Detection ； Acoustic Vibration ； Aluminum thin film

參考文獻

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