We propose a potentially practical scheme to precisely measure the charge number of small charged objects by using optomechanically induced transparency (OMIT) in optomechanical systems. In contrast to conventional measurements based on noise backaction on optomechanical systems, our scheme presents an alternative way to detect the charge number exactly, by monitoring small deformation of the mechanical resonator sensitive to the charge number of nearby charged object. The relationship between the charge number and the OMIT window width is investigated and the feasibility of the scheme is justified by numerical simulation with currently available experimental values.

A tunable double optomechanically induced transparency (OMIT) with a squeezed field is investigated in a system consisting of an optomechanical cavity coupled to a charged nanomechanical resonator via Coulomb interaction. Such a double OMIT can be achieved by adjusting the strength of the Coulomb interaction, and observed even with a single-photon squeezed field at finite temperature. Since it is robust against the cavity decay, but very sensitive to some parameters, such as the environmental temperature, the model under our consideration can be applied as a quantum thermometer for precision measurement of the environmental temperature within the reach of current techniques.

The optomechanics can generate fantastic effects of optics due to appropriate mechanical control.Here we theoretically study effects of slow and fast lights in a single-sided optomechanical cavity with an external force. The force-induced transparency of slow/fast light and the force-dependent conversion between the slow and fast lights are resulted from effects of the rotating-wave approximation (RWA) and the anti-RWA, which can be controlled by properly modifying the effective cavity frequency due to the external force. These force-induced phenomena can be applied to control of the light group velocity and detection of the force variation, which are feasible using current laboratory techniques.