Patent ID: 7049004

Claim:
A multi-cavity thin-film interference filter comprising a sequence of alternating layers of amorphous silicon and a dielectric material deposited one on top of the other to form a tunable bandpass filter, said dielectric material being selected from the group consisting of silicon dioxide and silicon nitride, said sequence of alternating layers forming coupled Fabry-Perot cavity structures including at least a first Fabry-Perot cavity structure and a second Fabry-Perot cavity structure, each of said first and second Fabry-Perot cavity structures comprising: a first multi-layer thin film interference structure forming a first mirror; a thin-film spacer layer deposited on a top surface of the first multi-layer thin-film interference structure, said thin-film spacer layer made of said amorphous silicon; and a second multi-layer thin film interference structure deposited on a top surface of the thin-film spacer layer and forming a second mirror; wherein said multi-cavity filter further comprises: a layer of electrically conductive material to which, during use, power is supplied by an external source to change the temperature of the multi-cavity thin film interference filter and thereby shift the passband of the multi-cavity thin film interference filter; and a substrate on which the first multi-layer thin film interference structure of the first Fabry-Perot cavity structure is deposited, wherein said layer of electrically conductive material forms a ring heater on the substrate and circumscribing an optical path through the first and second Fabry-Perot cavity structures.