Structuring Light Using Optical Fourier Transform For Particle Tracking and Live Cell Imaging

Abstract

Structured optical fields have had a profound impact in the optical sciences and have led to new discoveries in quantum communications [1], biological imaging [2] and spectroscopy [3]. The Optical Fourier Transformation (OFT) [4] is central to the development of novel structured optical fields [5]. To build structured optical fields using OFTs, a vast range of techniques was invented using modern spatial addressable optoelectronic devices [6]. The goal of this thesis is to study, design and implement novel OFT strategies to structure a variety of optical fields (uniform [7] and scattered [8]) for the purposes of enhancing single particle tracking and live cell imaging. Unlike existing implementation of OFTs that have primarily been restricted to uniform optical fields for light manipulation [9], I further developed OFT strategies to control scattered optical fields from thin layers of live cells [10]. In essence, I manipulated the intensities and phase distribution of scattered optical fields in thin biological samples to enhance an image or an optical signal in real-time. Hence, shaping the OFT through modern spatial addressable optoelectronic tools has heralded many advanced biomedical photonic tools including single molecule tracking [11], optical tweezers [9], fluorescence imaging and microscopy [6, 11-13]. The thesis is broadly separated into 8 chapters. In Chapter 1, I introduced the concept of the OFT as it relates to uniform optical fields used in beam shaping, imaging, and tracking, and further explain the formation of scattered fields of thin biological samples in microscopy imaging. In Chapter 2, I provided the mathematical treatment of OFTs for both coherent and incoherent optical fields, and the experimental considerations. In Chapter 3, I describe the practical implementation of spatial light modulators (SLMs) to modulate the OFT of both uniform and scattered fields. Chapter 4 describes how OFT is used to generate and modulate a coherent structured 2D intensity landscape. Chapter 5 describes the modulation of OFTs in both illumination and detection to enhance high speed single particle tracking in Back Focal Plane Interferometry (BFPI). Chapter 6 outlines a novel tunable widefield contrast using a nematic SLM. Chapter 7 describes a flexible switchable high-resolution highly inclined laminated oblique (HILO), Total Internal Reflection Fluorescence (TIRF) system with multi-spot Fluorescence Recovery After Photobleaching (FRAP) control for tracking intracellular fluorescence recovery The final chapter concludes by discussing the existing limitations of using OFT and future developments.