Atomic, Molecular and Optical Physics Seminar: Jinyong Ma, Australian National University, “Photothermal nonlinearity in optical cavities and optomechanical systems”

Event time: 
Wednesday, March 11, 2020 - 3:00pm to 4:00pm
Sloane Physics Laboratory (SPL), Room 56 See map
217 Prospect Street
New Haven, CT 06511
Event description: 

The nonlinear interaction between photothermal effects and optical cavities may have significant impacts on cavity-based applications. In the first part of this talk, I’ll present two novel effects we uncovered in a monolithic optical cavity strongly coupled to the photothermal effects. We propose and experimentally demonstrate an optically controllable transparency effect in an optical cavity strongly coupled to photothermal effects. We term this phenomenon “photothermally induced transparency” (PTIT). Because of the relatively slow thermal response, we observe the bandwidth of the PTIT to be 15.9 Hz, which theoretically suggests a group velocity of as low as 5 m/s. The second effect discovered is the optical modification of photothermal relaxation rate; that is, the intracavity optical field alters the natural photothermal relaxation rate as a function of cavity detuning.

The second part of the talk will be focused on the investigation of the nonlinear dynamics caused by photothermal interactions in an optomechanical system designed for optical levitation. A small free-standing mirror expected to be optically levitated acts as the top reflector of a vertical optical cavity, designed as a testbed for a cavity tripod optical levitation setup. We observe rich system dynamics inclusive of high-order sideband generation, optical bistability, parametric amplification, and optical spring effect. To counteract the system instability, we insert a laser window with Brewster’s angle inside the levitation cavity. The refractive index change of the window produced by photothermal heating tends to compensate for the change in effective cavity length caused by the thermal expansion of the levitation mirror. The result shows the way towards the stabilization of the optical levitation.
Host: Jack Harris