A tunable filter having a resonator with a resonant frequency dependent upon a variable gap is provided. The variable gap may be controllably altered by use of an actuator. The resonator is a high Q resonator that may be formed by a ring resonator, microsphere, microdisc, or other high Q optical structures. Actuation is preferably achieved through an electrostatic actuator that moves a dielectric plate relative to the resonator in response to measured values of gap and temperature.