Coherent Optical Property Of Toroidal Micro-cavity Optomechanical System And Its Application In Mass Sensing

The interaction between light and matter is always an important field in physics. Related breakthrough and innovation are emerging in an endless stream theoretically and experimentally. The research dimension is used to be of millimeter or centimeter, but with the development of nanotechnology, a variety of devices in nanoscale have been prepared in experiment such as quantum dot(QD), metal nanoparticles, semiconductor nanowires and micro-optical cavity, which make it possible to investigate the interaction between light and matter in nanoscale.Another important area in optics is the optomechanical system. The optomechanical systems in nanoscale, such as QD-nanomechanical resonator coupling system, DNA-QD coupling system and QD-spin coupling system, are proposed in succession. Nowadays, The cavity optomechanical system becomes a focus field due to its ultra high quality factor, ultra lightness, Ultra high frequency vibration and especially its convenient preparation process. In this article, we mainly investigate the whispering gallery mode(WGM) cavity optomechanical system. Basing on the optical pump-probe technique, we propose an all-optical mass sensing means with the WGM cavity optomechanical system.In Chapter One, we briefly introduce the concept and the history of optomechanical system. Next, we highlights the optical property of cavity optomechanical system. Through modulating the frequency and the power of the pump laser, optomechanically induced transparency and optical signal absorption and amplification can be obtained in cavity optomechanical systems driven by pump filed. Using this phenomenon, we can measure the frequency of mechanical resonator and use cavity optomechanical system as a mass sensor.In Chapter Two, we theoretically investigate the optical response of a cavity optomechanical system via the nonlinear coupling between optical and mechanical resonators, which is expected to be strong. Our results show that the nonlinear coupling will significantly influence the optical bistability. We compare the transmission spectrum of linear coupling with that of nonlinear coupling up to the second order and observe a shift between the transmission peak, which indicates the energy-level modification induced by the nonlinear coupling. Based on this nonlinear optomechanical phenomenon, we propose a theoretical method to determine the mechanical frequency and the second-order coupling constant.This means will eliminate the influence caused by the first-order coupling,which enables much easier detection of second-order coupling constant.In Chapter Three, we propose two mass sensing scheme basing on single WGM cavity and double-cavity systems, respectively. Classically,nanoparticles which are added to the surface of the WGM cavity will induce a frequency shift of the mechanical resonator. We can obtain the mass of the nanoparticles by measuring this shift in WGM cavities. Comparing these two different systems, we find that the detection sensitivity is raised when an optical cavity is coupled to the WGM cavity, which would make the cavity optomechanical system achieve better application performance.In Chapter Four, it is the main conclusions and prospect.