AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
A New Concept for Single Bioaerosol Particle Material Characterization
MATTHEW BERG, Mississippi State Univeristy
Abstract Number: 194 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract This work will present the development of a new photothermal technique to gather information related to a particle’s composition simultaneously with an image of it. Here, particles flowing in a sample stream are illuminated by a pulsed ultraviolet (UV) laser. This light combines across a detector with the light forward scattered by the particle. The resulting interference pattern constitutes a digital hologram, from which an image of the particle is reconstructed computationally. To obtain composition information, the particle is illuminated by the UV light twice in rapid succession while also being exposed to light from a pulsed infrared (IR) laser. Two holograms are thus formed on the detector. Performing the computational reconstruction on this double-exposed hologram yields an image of the particle superimposed with interference fringes. The fringes originate from any change in the particle’s physical state that occurs between the two UV pulses. Absorption of the IR light by the particle may cause photothermal expansion, and thus register as fringes in the reconstructed image. Since the degree of expansion depends on the light absorbed, the fringes indirectly convey information related to the particle material.