Novel optical micromanipulation techniques and applications of violet diode lasers

In this thesis, optical micro-manipulation experiments are described using laser sources spanning the wavelength region 1064 nm to 410 nm. Optical guiding is studied at near infrared wavelengths (780 nm) for comparison of a Gaussian and Bessel beam. The Bessel beam offers good transverse confinement. Extended guiding distances with the Bessel beam are shown with an enhancement factor of 3 over the Gaussian beam. Optical binding is observed in counter-propagating Gaussian beams using infrared light (at 780 nm and 1064 nm). In this geometry, the light-matter interaction induces particles to arrange themselves within a one-dimensional, regularly spaced particle array. A theoretical model is discussed to provide insight into the experimental data. Optical tweezing is performed using newly available short (violet) wavelength laser sources. The optical tweezers' trapping efficiencies were compared with a more traditional infrared source for tweezing. In addition, the violet lasers were used for biological spectroscopy, performing excitation of dyed chromosomes, and green fluorescent protein within cells. Finally, a violet microlensed diode laser at 413 nm is used with a microlensed diode at 662 nm for generating ultraviolet light in a non-linear sum frequency arrangement. This allows spectroscopy of atomic mercury at 254 nm to be performed

A dual beam photonic crystal fiber trap for microscopic particles

The dual beam counterpropagating optical trap has found increased use in studies such as optical stretching, optical binding, Raman spectroscopy, and the trapping of high index particles. In this letter we demonstrate the use of photonic crystal fiber to realize a long range dual beam trap that may support multiple wavelengths simultaneously. We develop a dual wavelength conveyor belt for trapped particles and realize the first ever dual beam white light (supercontinuum) trap. This low coherence light trap permits long range longitudinal optical binding of microparticles in the trap with no deleterious interference effects. (C) 2008 American Institute of Physics.</p

Selection and characterization of aerosol particle size using a bessel beam optical trap for single particle analysis

Bessel beams were used to create a counter-propagating optical trap for capturing and manipulating aerosol particles. Aerosol droplets were characterized through measurement of the elastic scattered light at three wavelengths; the trapping wavelength of 532 nm was used in conjunction with two probe beams at 405 nm and 633 nm to reduce the uncertainty in estimating droplet radii of 1 mu m or less. Control of the aerosol size distribution sampled by the counter-propagating trap was demonstrated by varying the trapping beam core diameters and intensities. Smaller droplet sizes were preferentially selected with a 1.7 mu m core diameter compared to cores of 2.7 mu m and 4.5 mu m. Further, an increase in core intensity was shown to broaden the range in droplet sizes that were optically trapped. The possibility of using such an approach to isolate and analyze the properties of single accumulation mode aerosol particles is discussed.</p