טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLevy Re'em
SubjectMicro Optical Resonator Levitating in Air
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Tal Carmon


Abstract

In 2018, Arthur Ashkin won the Nobel Prize for his 1969 discovery of optical tweezers. Ashkin was also the first to observe radiation resonance in droplets [1]. The resonating light in Ashkin's droplet resulted in an upward, counter gravity, motion of the droplet. 

Today, liquid micro resonators are being used to explore a variety of optical effects. They are relatively easy to fabricate and have an exceptionally smooth surface by nature which minimize scattering losses. Moreover, liquid resonators are usually small in size and can host high intensity optical modes featuring optomechnical interaction such as capillary and acoustic effect [2], [3]. The possibility to manipulate liquid resonators is another advantage compared to solid micro resonators. The first micro resonator to be controlled by optical tweezers in aquatic environment was demonstrated in our lab [4].

In this thesis, we present indication of lasing, counter propagating modes induced by Rayleigh scattering, repetitively of resonances, and coupling variation on an optical levitating micro resonator, in air. Optical tweezers were used to trap a silicon oil droplet in air. We excite and monitor optical Whispering Gallery Mode (WGM) in the levitating droplet. The first activation of such micro resonator was first done in our lab as well. Here, we show an upgraded optical tweezer for levitating micro resonators which allow for more stable trapping, longer resonance excitation periods, and deeper optical effects of the levitating resonator.

By upgrading the optical system, we were able to observe and measure counter propagating modes of the resonator and to characterize the behavior of a group of overlapping modes. The droplet resonator we explored feature a  Q-factor and over a million finesse value. The levitating droplet is the most spherical micro resonator shown to-day, so as recorded enhancement to size (Q/V) of micro sphere resonators.

The unique qualities of the levitating micro resonator make it suitable for high precision sensing device. Optical circuits are also a possible application for this kind of resonators.