Preferred locations in a laser beam for photophoretic trapping of microscopic particles

Michael Ware; Aaron Peatross; Daniel Smalley; Daniel Tveten; Justin B. Peatross

doi:10.1117/12.2596791

3 August 2021 Preferred locations in a laser beam for photophoretic trapping of microscopic particles

Michael Ware, Aaron Peatross, Daniel Smalley, Daniel Tveten, Justin B. Peatross

Proceedings Volume 11798, Optical Trapping and Optical Micromanipulation XVIII; 1179826 (2021) https://doi.org/10.1117/12.2596791
Event: SPIE Nanoscience + Engineering, 2021, San Diego, California, United States

Abstract

Photophoresis can trap opaque microscopic particles in a focused laser beam surrounded by a gas such as air. The particle is heated by the laser, and in turn, interactions with the ambient gas provide a stabilizing force that holds the particle in a specific region of the beam. The particles can stay trapped while the beam ismoved side to side up to 2 m/s, enabling three-dimensional images to be traced out in a display application. Structure in the laser beam is associated with the trapping phenomenon, but the fundamental mechanism for stability of the trap remains mysterious. Particles prefer regions of the beam with diffraction features such as those that arise from spherical aberration. Nevertheless, the ability of near-unidirectional light, albeit light that undergoes focusing and exhibits structure, to provide a restoring force to trapped particles in the direction opposite to beam propagation needs to be explained. Through repeated trials of capturing particles in a well characterized beam, we map out the preferred locations for particle capture and correlate them with diffraction features of the beam. The specific beam locations that host trapped particles, when compared with neighboring regions that do not, can offer insight into the stability mechanism. We analyze the Poynting vector in the vicinity of trapped particles. The flow of light energy can provide important clues into the trapping mechanism.

Conference Presentation

Citation Download Citation

Michael Ware, Aaron Peatross, Daniel Smalley, Daniel Tveten, and Justin B. Peatross "Preferred locations in a laser beam for photophoretic trapping of microscopic particles", Proc. SPIE 11798, Optical Trapping and Optical Micromanipulation XVIII, 1179826 (3 August 2021); https://doi.org/10.1117/12.2596791

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