Study of optical trapping and optical phase conjugation microscopy

Optical traps offer an unprecedented means to manipulate samples on a microscopic scale. This dissertation studies optical traps integrated with various optical systems, including fluorescence detection and optical phase conjugation microscopy to explore the rich possibilities offered by optical trapping in biology.; A scanning optical laser trap with fluorescence excitation and emission capability has been implemented in a flow cytometric geometry to study microparticle confinement and off-axis fluorescence detection in laminar flow streams. Particle escape velocity, trapping efficiency, and fluorescence intensity are measured for 2 {dollar}mu{dollar}m diameter dye-tagged latex microspheres in laminar flow rates of up to 10 mm/s. Experimental results are compared with theoretical estimation of flow velocity and fluorescence intensity and found to be in agreement. The stability of trapping and fluorescence detection in flow streams are also discussed.; In another experiment, optical trapping is combined with optical phase conjugation microscopy for simultaneous trapping and image processing functions. The first experimental implementation of a self-aligned dual-beam trap using optical phase conjugation is demonstrated. Transverse trapping efficiency is measured in this new configuration. Ray optics approach is used to calculate the axial trapping efficiency for a phase conjugate trap and the results are compared with that of a single beam gradient trap, as well as that of the conventional counter-propagating two beam trap. It is found that the trapping efficiency of a phase conjugate trap is comparable to that of the single-beam trap, with slight improvement.; We demonstrated simultaneous trapping and image processing capabilities in the wavelength of 514.5nm, at which phase conjugation process is efficient, but biological samples suffer damages due to strong absorption. Near infrared (NIR) wavelength is a better choice. Optical phase conjugation process in NIR is studied and the dependence of the reflectivity and rise time of phase conjugation on parameters including incident angles, positions and beam power is presented. Features of phase conjugate image processing combined with micromanipulation capability provided by optical tweezers are potentially useful for the study of biological organisms. However, the efficiency of phase conjugation process in NIR wavelength needs to be significantly improved.