AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Optical Configurations for Photophoretic Trap of Single Airborne Particles in Air
ZHIYONG GONG, Yong-Le Pan, Chuji Wang, Mississippi State University
Abstract Number: 381 Working Group: Single Aerosol Particle Studies - Techniques and Instrumentation
Abstract Optical trapping has become an emerging tool in single aerosol study. Different from optical tweezers, which employs a tightly focused beam to trap non-absorbing particles, photophoretic trapping is able to trap a variety of light absorbing particles due to the strong photophoretic force (PPF) induced by the differences in the surface temperature and accommodation coefficient of the particle. There are plenty of complicated trapping schemes based on PPF available for aerosol research. We demonstrate six different types of simple schemes to explore the full potential of diversity of the photophoretic trapping. Their 21 variants are constructed by varying instrumental parameters, e.g., laser source, power, beam shape, and focusing optics. The trapping performance and quality of those trapping schemes are evaluated in terms of four key aspects: simplicity, robustness, flexibility, and efficiency. Among the six types of schemes, some of which have been reported before; but a new, simple single-beam scheme using the confocal design is introduced, in which one trapping beam is converted to two virtually counter-propagating beams. This new and versatile trapping scheme has the leveraged advantages of the single-beam traps and the robustness of the counter-propagating beam traps. The new trapping scheme is further integrated into the cavity ringdown spectroscopy technique to show application of the photophoretic trapping. The detailed design, construction, and evaluation of the six types of trapping schemes and their 21 variants may offer researchers of interest a freedom of choice in their own applications of optical trapping.