介電質微米球透鏡之超解析成像機制研究

Abstract

傳統光學顯微鏡被普及運用在物理、化學、生物等眾多領域，然而其解析度受到Abbe繞射極限限制約為入射光波長的一半(Resolution = λ/2)。現今有許多學者在研究克服繞射極限的技術，例如近場掃描式光學顯微鏡、螢光顯微法或者負折射率超穎材料製造的hyperlens等等。然而耗時的影像擷取，螢光短暫的生命週期以及複雜精密的製程卻成為在應用上的致命傷。近年來，許多實驗證實介電質微米級小球可以以簡單方便的方法在可見光波段解析繞射極限下的樣本。在我們的研究中，研究了微米球成像的條件，幾何的形狀或者測試以不同折射率的浸泡液體與小球，以不同方法嘗試製作可以方便轉移的微米球陣列透鏡，其最佳解析度可以達到λ/7.5，且能提供較廣的視野範圍與廣角度的成像。另外我們也設計實驗並排除消逝波或whispering gallery modes為介電質微米球超解析成像的機制。

The resolution of conventional microscope is restricted to about λ/2 by the Abbe diffraction limit. There are some approaches to overcome the diffraction limit nowadays, e.g. near-field scanning optical microscopy, fluorescent microscopy, and negative index materials. However, these techniques suffer by slow scanning speeds, short-lifetime of fluorescent dyes, and sophisticated fabrication processes. Recently, it has been shown that dielectric microspheres can bring the sub-wavelength information to far-field, achieving super-resolution using a white-light source. Here, we demonstrate that partially-immersed dielectric microspheres are capable of offering broadband, large field-of-view, and wide-angle super-resolution (at least λ/7.5) images. We also exclude evanescent waves and the effects of resonant whispering gallery modes to be the mechanism of super-resolution. Importantly, we show that microspheres of different materials can easily reach super-resolution for a large range of diameters without complicated fabrication.