Study Of Mass Sensing In Optomechanical Systems

As one of the basic nature of physical objects,the precision measurement of mass is very important for the fundamental of physics.At the same time,the same thirst to microscopic objects become stronger along with people exploring the micro world.Nanomechanical oscillator has developed to be a very useful platform for its miniaturization and high frequency of vibration.The theory and experiments of mass sensing based on nanomechanical systems have attracted a lot of attentions for their exciting achievement.However,object to be measured by electricmechanical systems would be heated by the electric current,which limits its application in biological field.Optomechanical systems,coupling mechanical oscillator with optical mode by radiations,can operated in all-optical way to avoid electric heat.The relation between the mass and frequency of mechanical oscillator is also the key for mass sensing in optomechanical systems.Optomechanical systems manipulate the mechanical oscillator by light,which can borrow the nonlinear optical response.But this kind of all-optical way would come to a limit induced by the linewidth of mechanical oscillator.We propose a few schemes of mass sensing to break through this limit,which is also based on the optomechanical systems.Our proposes have great potentials in mass sensing and techniques relied on the precision measurement of frequency of mechanical oscillator.Our study can be specifically divided into three parts:1.We propose a method of enlarging a minute mechanical frequency shift to enhance the sensitivity of mass sensor.This enhancement would rely on the quantum criticality which can realized in optomechanical systems.The normal mode induced by this quantum criticality is very sensitive to small mechanical frequency shift.Detection of normal mode can be simply implemented by a weak coherent drive.Since the improvement is enormous,frequency shift of mechanical oscillator smaller than the linewidth,i.e,1 Hz,can be resolved by our propose.2.We improve the sensitivity of mass sensor by replacing the weak coherent drive by quantum light.The quantum light here means a weak light with strong second-order coherence,which is very sensitive to small change of nonlinearity induced by small mass change.The quantum criticality is not only induce a sensitive normal mode but also a strong nonlinearity connecting the mass change.Comparing with the weak coherent light source,the quantum light can make a signal in the strong decay of cavity.Our simulation operate in the experimental parameters,and we believe this propose would provide a new path to mass sensor.3.We study the application of high-order sidebands in optomechanical systems to enhance the resolution of mass sensor.The idea is a very simple generalization of the all-optical way in optomechanical systems.The order of sidebands is higher,the performance of mass sensor would be better.To make progress with this goal,we focus on the generation of high-order sidebands when the system is under two-color driving.For examples,the resolution would be the linewidth of mechanical oscillator when the all-optical way is considered.However,the resolution can be improve to be a twentieth of the linewidth,when we adopt 20-order sidebands to make a detection.This propose work on the similar principle with the all-optical way but in the higher order sidebands.Our study might inspire the application in both high-order sidebands and mass sensor.In conclusion,we propose some new methods to improve the resolution of mass sensor based on the optomechanical systems.Our study range from quantum to classical domain.The application of quantum criticality and quantum light would inspire the technique in mass sensor.