Tunable fabry-perot filters and lasers with reduced frequency noise

Abstract

A tunable optical cavity constructed from a fixed mirror and a movable mirror. The fixed mirror is attached to a substrate having a first electrically conducting surface. A support member having the moveable mirror supported thereon and having a second electrically conducting surface, is suspended above the substrate. A circuit applies an electrical potential between the first and second electrically conducting surfaces thereby adjusting the distance between the fixed and movable mirrors. The fixed mirror and the moveable mirror are positioned such that the mirrors form the opposite ends of the optical cavity. The distance between the fixed mirror and the moveable mirror is a function of the applied electrical potential. The support member has physical dimensions that are chosen such that the amplitude of thermally induced vibrations in the support member are less than 0.01 percent of the wavelength of the resonating light. The support member is preferably a thin film membrane having the moveable mirror attached thereto and having openings communicating between the top and bottom surfaces of the membrane. The openings are located so as to reduce the vibration amplitude of the moveable mirror at any mechanical resonances of the membrane. The openings occupy less than 90% of the surface area of the membrane.