Importance

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Abstract

A method and apparatus for a micromechanical modulator having a reduced-mass multilayer membrane is disclosed. The modulator includes a movable composite membrane suspended over a subtrate. The composite membrane consists of an overlayer and an underlayer. The overlayer is characterized by a thickness that is less than one-quarter of a wavelength of the optical signal being modulated. Under the action of a bias voltage, the movable membrane moves from a quiescent position to a second position closer to the substrate. The modulator is fabricated so that in either the quiescent position or the second position the gap between the composite membrane and the substrate is equal to d=m.lambda./4-n.sub.s s when n.sub.u is about equal to (n.sub.s) .sup.0.5, where m is an even integer, .lambda. is the wavelength of the optical signal being modulated, n.sub.s is the refractive index of the subtrate, n.sub.u is the refractive index of the underlayer, n.sub.o is the refractive index of the overlayer, and s is the thickness of the overlayer. More generally, the gap may be given by d=m.lambda./4-n.sub.s s+(n.sub.u -n.sub.s.sup.0.5) (.lambda./10) sin (4.pi.n.sub.o s/.lambda.).

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First Claim