矽奈米天線陣列設計與製作之窄頻高吸收元件

Abstract

高折射率材料所製作的奈米結構，由於可以利用入射電磁波產生電偶極(ED)與磁偶極(MD)，而可以提供一個控制散射訊號，並達到窄頻高吸收峰的機會。本論文提出，利用非晶矽奈米天線陣列可以實現近紅外光高吸收的元件，這個高吸收元件是利用調整陣列的週期來激發晶格共振，控制電偶極與磁偶極使兩者重合，來抑制背向與前向散射。此外，利用非晶矽奈米天線陣列所產生的吸收比起非晶矽薄膜高了三倍，在光學頻譜上可達到接近90%的吸收，且這個高吸收的特性並非只是由於材料本身的損耗，而是主要產生自電偶極與磁偶極的交互共振所造成的侷域電場以及吸收增強。

High-refractive-index nanostructures support optically induced electric (ED) and magnetic (MD) dipole modes which offer opportunities to control the scattering and achieve the narrowband absorption. In this work, the high absorptance device is proposed and realized by using amorphous silicon nanoantenna arrays (a-Si NA arrays) which suppress backward and forward scattering with engineered structures and particular periods. The overlaps of ED and MD resonances by designing an array with a specific period and exciting lattice resonances is experimentally demonstrated. The absorptance of a-Si NAs which is 3-fold increase in comparison to unpatterned silicon films. The nonradiating a-Si NA arrays can achieve ~ 90% in absorptance, and the high absorptance resonance is observed not only due to the intrinsic loss of material but by overlapping the ED and MD resonances.