Enabling quantum optomechanics for phononic crystals and superfluid helium films

Abstract

We are familiar with a macroscopic world that follows the laws of classical physics, whereas the behavior of microscopic particles such as atoms and electrons is described by quantum mechanics. A long-standing question is when, and by what mechanism, quantum systems lose their quantum properties as their size increases. Cavity optomechanics, which exploits the interaction between light and mechanical motion to precisely measure and control mechanical systems, has become an important experimental platform for addressing this question and for exploring a wide range of physical phenomena in microscopic mechanical systems. It has found important applications in macroscopic quantum state preparation, precision measurement, and nonlinear dynamics.

This thesis presents two cavity optomechanics experiments. The first experiment uses light to measure and cool an ultrathin (25 nm) silicon nitride membrane, providing a foundation for future studies of quantum phenomena at macroscopic scales. The second experiment investigates a superfluid helium film condensed on the surface of an optical resonator and explores the complex dynamical behavior that emerges under optical excitation. Together, these two experiments focus on macroscopic quantum phenomena and nonlinear dynamics, illustrating the versatility of cavity optomechanics across different research directions.