LIGHT FIELD MANIPULATION VIA ENGINEERED MICROSPHERE FOR OPTICAL NANO-IMAGING

Abstract

An optical microsphere nanoscope is a method that can significantly enhance the observation power of conventional optical microscopes. However, the microsphere still faces restrictions including limited focal length and depth, restricted working plane, and relatively low imaging contrast. In this thesis, three ways of engineered microsphere schemes are proposed to improve on these aspects. Firstly, a negative axicon microsphere is developed to generate a significantly elongated (six-fold) focused region of light. Secondly, Fresnel zone microsphere is introduced to achieve wavelength-dependent switching of states between spatially continuous and discrete focusing of light. The third topic is by placing a pinhole at the conjugate image plane of the virtual image of the sample, unwanted background noise is spatially filtered out, and the imaging contrast is enhanced. The proposed engineered microsphere schemes can enhance the functionalities of this micro-optical platform and may pave the way for an easy-to-use and generalized nano-imaging system.