Design and Implementation of an Optical Cavity Locking Controller Test Bed System

This paper describes a new optical cavity controller test bed system for implementing modern quantum control techniques, with an emphasis on the control of optical cavities. One such quantum control task is the frequency locking of an optical cavity. Locking an optical cavity refers to the process of matching the input laser frequency to the cavity's resonant frequency. Any deviation in the two frequencies, characterized in terms of the detuning, is undesirable. The test bed comprises an input laser, a three-mirror ring cavity, the associated optics, and a dSPACE digital signal processing system. The detuning in the system is measured in the form of an error signal, which is fed to a controller. The controller provides a suitable control input to a piezoelectric actuator mounted on one of the mirrors, altering the resonant frequency of the cavity to achieve zero detuning. The dynamics of the cavity and the piezoelectric actuator are modeled using system identification methods, an integral linear quadratic Gaussian controller is designed and implemented in dSPACE, and experimental results are presented.