透過二維光子晶體來監控二維奈米級的位置變化

Abstract

在本論文中，我們提出一套簡易及低成本的干涉系統，藉著由偵測二維六角型光子晶體玻璃基板來即時監控二維之奈米等級位移量。這個即時監控二維奈米等級位移量的方法，是將波長為633-nm的氦氖雷射光源正向入射一個二維六角型光子晶體玻璃基板來產生遠場繞射光束。基板在作二維移動時，六道繞射光束的光場相位會隨著光子晶體玻璃基板的位移向量來作線性變動。當我們取兩道一階繞射光束與零階光束在兩個正交平面上形成二維的干涉圖形，利用CCD讀取並作訊號處理來量得移動前後之相位差，即可推算出裝置基板之移動平台的位移量，其量測二維位移量之準確度可到達奈米等級。最小可測量的位置變化量會與作為繞涉光柵的光子晶體之週期大小有關，而我們所用的二維光子晶體週期約為1.28μm，最小可量測的位置變化量可到20nm。

In this thesis, simultaneous two-dimensional nanometric-scale position monitoring is achieved in a simple and cost-effective interferometric setup by real-time probing a two-dimensional hexagonal photonic crystal glass substrate. To real-time monitor the two-dimensional translational movement in nanometric-scale, an optical imaging system is built by probing a hexagonal photonic crystal glass (HPCG) with a 633-nm He-Ne laser beam. The translation movements in both directions are recorded in the phases of the fields of the diffracted six spots in a linear relation. By carefully aligning the two first-order spots and the zero-order spot to form chessboard-like interference pattern on the CCD camera, the individual nanometric-scale movement information can be determined by the phase change of the chessboard-like interference pattern before and after moving. In principle it can attain the nanometric-scale accuracy of position reading in both orthogonal moving directions. The minimum detectable translational movement is dependent on the period of the probed photonic crystal (1.28μm in this study) and can be down to 20nm as demonstrated in the present work.