Optical levitation and Mie Fano combs

Abstract

The smallest component of light, the photon, carries a small amount of momentum. When matter refracts, reflects, or absorbs light, some of this momentum is transferred to it, meaning that light can push or even pull matter. This fact was used by Arthur Ashkin in his invention of optical levitation and optical tweezers, which merited him a Nobel prize in 2018. The range of applications of optical tweezers is huge, ranging from trapping cells and organelles to creating quantum-limited sensors.

This thesis expands the applications of optical levitation through 6 new experiments using a vertical, single-beam trap and a horizontal, 2-beam counter-propagating trap. With the vertical trap, I created a fully-manipulable damped driven harmonic oscillator and visualized the spherical aberration of a lens. I also re-created the 116-year-old Millikan experiment with a single oil droplet, where single electrons can be observed by eye and measured with a school ruler.

Then, with the counter-propagating trap, I studied the Mie scattering of evaporating water droplets, showing the existence of a comb structure made up of Fano resonances. I used this to propose a new pedagogical example to teach quantum mechanics, and to explore the effects of strong irradiative heating on evaporating droplets, where I find a turnover in the evaporation rate of droplets.

The wide range of topics covered in this thesis shows the huge versatility of optical levitation as a research tool. It also provides an intuitive understanding of the structure of the resonances in Mie scattering and showcases how this spectrum can be applied to other fields such as droplet evaporation and physics education research.