Mechanical Resonator Cooling In Cavity Optomechanical System

It has always been a dream of physics that a single particle can be measured and then obtain its inner states.Fortunately,laser cooling technology makes the dream come true.Laser cooling technology can quickly cool the single particle to the ground state,which is the wished quiet particle.When measuring such quiet particle,we can gain the information of the inner states with high precision.The deep knowledge we know about the particle can greatly promote the development of the fundamental physics.Furthermore,the laser cooling technology has already been widely used in the field of high precision measurement.The thesis mainly studied the cooling problem about nano-mechanical resonator in the cavity optomechanical system.Nano-mechanical resonator has both properties of classical and quantum theory,which is an important issue of studying the relation of classical and quantum theory.With the development of the nano-technology,the nano-mechanical resonator,which has very high sensitivity,can be made and applied to high precision measurement.We are able to cool the nano-mechanical resonator to its mechanical ground state,however,it has much high request about the dissipation rate of cavity.To overcome this problem,we investigate the ground state cooling scheme assisted by an atomic ensemble,there is no request of cavity's dissipation rate and we can obtain the lower cooling limit just by change related coupling strength in our scheme.We have verified that the cooling rate can be increased by strengthen the pump laser when the cavity-mechanical resonator coupling is week,and we also have discussed the cases when the cavity-mechanical resonator coupling is strong.