| dc.description.abstract | The breadth of applications of optical tweezers in life sciences is so large, that it
merited Arthur Ashkin a Nobel prize in 2018. Although optical levitation in air
was invented first, it has not managed to be so widely adopted as optical tweezers. Here, I present 4 different applications to showcase the versatility of optical
levitation.
First, I show the forces acting on a particle through the construction of a fully
manipulable damped driven harmonic oscillator. The transition from the over- to
under-damped regimes is clearly recognizable and a big harmonic resonance can
be observed by eye.
Second, to measure the particle’s displacement in the previous experiment,
we focused the scattered light with a lens. Here, I noticed an intriguing spider
pattern that we fully explain by analyzing the spherical aberration of the lens. This
resulted in a clear visualization and measurement of optical aberrations.
Third, once we were free of aberrations, we were able to measure minute
movements of the particle. This allowed us to create a modern version of the Millikan experiment where we add individual electrons to a single levitated droplet
and observe the quantization of the electron by eye.
Fourth, as the droplets evaporated we found a fascinating pattern in the scattering intensity. This turned out to be a directional Mie scattering spectrum with
over 100 evolving Fano resonances arranged in a comb structure. We intuitively
describe this spectrum through a quantum mechanical analogy to a spherical well
potential. This converts our experiment into a “toy atom” where we see quantized
angular momentum, ground and excited states, and tunneling.
Through these 4 different applications, I provide an overview of optical levitation and its wide applicability | en_US |
