|Ph.D Student||Douvidzon Mark|
|Department||Department of Nanoscience and Nanotechnology||Supervisor||Professor Tal Carmon|
|Full Thesis text|
The confinement of light and sound enables a variety of light-matter interactions.
Therefore, it is natural to ask if optical devices can also host capillary waves. Capillary waves are similar to those we see when throwing a stone into a puddle. Such capillary waves are prohibited in most microfluidic devices where the liquid is bounded by solid walls. In contrast, we have fabricated two optical devices which are not bounded by any solid: 1) An optical fiber made entirely out of water hanging in air and 2) an ultra-soft micro-resonator submerged in water.
As for the water fiber: It can move in a resonant mode that reassembles the motion
of a guitar string but with restoring forces related to surface tension at the liquid/air
boundary and not to the solid elasticity. In our experiment, light guided through
the water fiber allows optical interrogation of is capillary oscillations. We report its
fundamental oscillations and three higher harmonics. The softness of the water fiber
is a million times higher when compared to what the current solid-based technology
permits, which accordingly improves its deformation by minute forces, such as small
changes in acceleration.
As for the ultra-soft micro-resonator: We use oil in water and reduce its interfacial
tension by another million times in comparison to the already soft water fiber. Our
resonator is in fact so soft, that we are limited by the Brownian motion, which breaks
our device. At this softness we can deform the resonator at will with optical tweezers
while coupling light into it through an optical tapered fiber. We report six asymmetrically deformed optical cavities, the associated mode split, mode mapping and direct light emission.
Additionally, we developed a method to measure the capillary amplitude, resonance
spectrum, and damping of the deformed droplet. Co-confining two important oscillations in nature: capillary and electromagnetic, might allow a new type of devices called Micro-Electro-Capillary-Systems [MECS]. The softness of MECS is a 106 − 1012 times higher when compared to what the current solid-based technology permits. MECS might allow new ways to optically interrogate viscosity and surface tension, as well as their changes caused by introducing an analyte into the system