應用於可見光波段的砷化鎵超穎表面

Abstract

近年來，隨著3D感測器的應用範圍擴展到手機等攜帶式裝置的應用上，傳統3D感測器體積大的問題需要得到解決。傳統3D感測器是由許多透鏡組合而成，因此體積上較大也較笨重，如果使用的是超穎表面，將可以大大的縮小體積，對於整合進攜帶式裝置也較方便。因此本論文將利用超穎表面解決傳統光學元件體積大、重量重，功能較單一的缺點，並開發特殊的渦漩結構光，未來可應用在3D感測上。 本實驗為利用優化結構之砷化鎵奈米柱，並結合幾何相位分佈設計法(Pancharatnam-Berry Phase)，開發出直徑分別為100微米以及50微米的砷化鎵超穎表面。砷化鎵奈米柱尺寸優化，為使用CST光學模擬系統進行數值模擬。在製程上，為了達到高深寬比的砷化鎵奈米柱，使用了感應耦合式電漿蝕刻(ICP-RIE)進行電漿蝕刻，該機台是一種能夠實現高深寬比的乾式蝕刻機台，我們在蝕刻參數上進行優化。並透過電子顯微鏡進行檢測，確保砷化鎵奈米柱的尺寸符合我們的設計。最後，在光學量測上，進行光強度的分析，以及使用馬赫-曾德爾干涉儀(Mach–Zehnder Interferometer)進行光干涉的量測。

In recent years, with the expansion of the 3D sensing applications to portable devices such as mobile phones, the issue of the large size of traditional 3D sensors needs to be addressed. Traditional 3D sensors are composed of multiple lenses, making them bulky and heavy. By utilizing metasurfaces, the feature sizes of devices can be significantly reduced, making integration into portable devices more convenient. Therefore, this work aims to utilize metasurfaces to address the drawbacks of large size, heavy weight, and limited functionality in traditional optical components, and to develop specialized vortex-structured light that can be applied in future 3D sensing applications. This study focuses on utilizing optimized gallium arsenide (GaAs) nanofins together with the Pancharatnam-Berry Phase design principle to develop metasurfaces with diameters of 100 and 50 µm, respectively. The optimization of GaAs nanofin dimensions was carried out using the CST software for numerical simulations. In the fabrication process, in order to achieve high-aspect-ratio GaAs nanofins, inductively coupled plasma reactive ion etching (ICP-RIE) was employed for plasma etching. ICP-RIE is capable of achieving high-aspect ratios in dry etching, and we optimized the etching parameters. Verification of the GaAs nanofin dimensions was conducted through scanning electron microscope (SEM) to ensure they matched our design. Finally, in terms of optical measurements, an analysis of light intensity was conducted, and a Mach–Zehnder Interferometer was used to measure optical interference.