Study On Optomechanically Induced Transparency And Fast-slow Control In An Optomechanical System With Multiple Mechanical Resonators

The research of controlling macroscopic mechanical objects in deep quantum regime has aroused interest.It can be used to reveal the principle of photon-phonon interaction in optomechanics and promote experimental research on quantum nanodevices.Generally,in an optomechanical system,people use high quality factor mechanical resonators to couple with optical cavities.And there are various forms of subsystems of optomechan-ical systems,such as Bose-Einstein condensation inside two optical cavities,two fixed mirrors,a micromechanical membrane,a fixed mirror and another movable mirror,two optical cavities,and a photonic crystal system.The optical properties of these systems show that coherent effects in optomechanical systems are similar to those in atoms.This phenomenon similar to electromagnetically induced transparency is known as optome-chanically induced transparency and it can be explained as:quantum interference in the anti-Stokes sideband path and the cavity field photon transition path makes the system no longer absorb weak probe light.In this thesis,we investigate the change in width of transparency windows and the amplification phenomenon of the probe output spectra in an optomechanical system with multiple mechanical resonators.Each mechanical res-onator is driven by an external mechanical driving field and the phases of these external mechanical driving fields are adjustable.First,the various properties of the probe output spectrum in an optomechanical system with multiple mechanical resonators are studied.For example,the absorption of the probe output spectrum and the optomechanically induced transparency behavior.Under the red-detuning regime,when there is a single mechanical resonators in the optomechanical system,only one optomechanically induced transparency window appears in the probe output spectrum.When the number of mechanical resonators in the optomechanical system increases,the number of optomechanically induced transparency windows in the probe output spectrum also increases,and the number of optomechanically induced transparency windows corresponds to the number of mechanical resonators.At the same time,there is a slight difference in the frequency of each mechanical resonators.This paper also studies when there are multiple mechanical resonators with the same frequency in the optomechanical system.In the probe output spectrum,we can easily find that only one optomechanically induced transparency window appears.However,due to the presence of multiple mechanical resonators,the coupling strengths between the mechanical resonators and the optical cavity will be enhanced,which causes the optomechanically induced transparency window width to become wider.The influence of other factors on the probe output spectrum of the system is further studied in this paper,such as the change in the cavity decay rate and the effect of external mechanical driving field on the probe output spectrum.We can clearly observe that as the cavity decay rate increases,the optomechanically induced transparency window in the probe output spectrum gradually narrows.When each mechanical resonator is driven by an external mechanical driving field,the shape of the optomechanically induced transparency window of the probe output spectrum changes significantly.In the following,we study a series of novel phenomena caused by the phases change in the external mechanical driving fields.We take two mechanical resonators in this optomechanical system as an example.When the phase of only one of the mechanical driving fields is changed,an amplification dip appears on one side of the probe output spectrum of the optomechanical system.Meanwhile,when a particular value of the phase is selected,the amplification dip reaches a maximum value.However,the height of the absorption peak on the other side is fixed.This also proves that when the phase of each external mechanical driving field is adjusted separately,the optical properties of the system can be controlled more flexibly.In addition,we continue to study the effect of changes in the phase of the external mechanical driving field on the group delay.When the phase of the first mechanical driving field is kept unchanged,the phase of the other mechanical driving field is changed.The change tendency is:as the phase value of the second mechanical driving field increases,the value of the group delay changes from negative to positive.This means that the fast light effect turns into a slow light effect.When the phase of the first external mechanical driving field is another value,the change tendency is just the opposite.It also better proves that when the phase of the external mechanical driving field is adjusted separately,we can more flexibly control the optical properties of the optomechanical system.