Patent ID: 6522469
Filing Date: 2003-02-18
Classification: G02B,G02F

Abstract:
A thin film optical filter for receiving incident light and for transmitting transmitted light from the received incident light within a passband and for reflecting reflected light from the received incident light outside the passband, the thin film optical filter comprising,an external voltage source for providing an applied voltage, an electrooptical dielectric having a thin film thickness and an electrooptical refractive index for receiving the applied voltage and for communicating the transmitted light and for supporting an electrical field created by the applied voltage, the electrooptical refractive index being controlled by the applied voltage, an upper stack of thin film upper layers disposed on the electrooptical dielectric, the upper layers of the upper stack having respective thin film thicknesses and respective refractive indices so that each of the uppers layers reflect a portion of the incident light so that the upper layers reflect an upper reflected portion of the incident light during transmission and reflection of the incident light, and a lower stack of thin film lower layers, the lower layers of the lower stack having respective thicknesses and refractive indices so that each layer reflects a portion of the incident light so that the lower layers reflect a lower reflected portion of the incident light, the lower reflected portion cancels the upper reflected portion of the light so as to reduce the reflected light and increase the transmitted light within the target passband when the electrooptical dielectric is controlled by the applied voltage during transmission when the electrooptical dielectric has a thickness and refractive index that adjusts the phase of light passing through the dielectric so as to adjust the phase of the lower reflected portion relative to the higher reflected portion for increasing cancellation of the upper reflected portion for increasing the transmitted light within the passband while decreasing the reflected light within the passband, the applied voltage serving to shift the passband, the transmitted light being within the passband in the presence of the applied voltage and outside the passband in the absence of the applied voltage.