Optomechanical isolation with tunable center frequency

Abstract

Optomechanical (OM) isolators have the ability to stop the optical field for one direction and to pass the field in the opposite direction. Thus they work as bandstop filter in one direction and bandpass filter in the opposite direction. The maximum isolation happens when the frequency of the field becomes equal to that of the mechanical membrane inside the isolator. This frequency, called the isolation (or center) frequency, however is restricted by the fact that the fundamental frequency of the membrane depends upon its physical parameters (such as mass and length), which are fixed during fabrication of the membrane. We propose a dynamical way of tuning this center frequency, by using a mechanical drive attached to a membrane with quadratic OM coupling in a membrane-in-the-middle setup. This provides a way for future applications where tunable filtering is required.