Optical thin-film cavities for transducing visible radiation to infrared radiation

Abstract

A transducer is deposited on each fiber of an optical fiber scene projector to convert portions of electromagnetic radiation to emitted radiation, h as IR. The transducer, is adaptable to large arrays of optical fibers and can be fabricated using mature conventional processes, such as vapor deposition, for example. The components of the transducer can be tailored to handle different incident radiation and produce desired emitted radiation. Dielectric layers having thicknesses equal to odd-numbered multiples of quarter wavelengths of the electromagnetic radiation receive the electromagnetic radiation and a reflector adjacent to the layers reflects unabsorbed portions of radiation back through the layers. An absorber layer interposed between adjacent dielectric layers absorbs the received and the reflected radiation so as to convert the absorbed radiation into heat energy. Second dielectric layers having thicknesses equal to odd-numbered multiples of quarter wavelengths of desired emitted radiation are deposited adjacent to the reflector. A second absorber layer interposed between the adjacent layers of the second dielectric layers absorbs the heat energy and converts it to the emitted radiation, such as IR, although, other wavelengths could be emitted depending on the dimensions and materials used. Different number of layers may be included as needed to modify the emitted radiation.

We claim: 
     
       1. A transducer comprising: first dielectric layer to receive electromagnetic radiation, each layer having thickness equal to an odd-numbered multiple of quarter wavelengths of said radiation;   a reflector adjacent said layers to reflect portions of said radiation to said layers;   first film interposed between adjacent dielectric layers to absorb said received and said reflected radiation and to convert said absorbed radiation to heat energy;   second dielectric layers adjacent said reflector to receive said heat energy, each layer of said second dielectric layers having thickness equal to an odd-numbered multiple of quarter wavelengths of desired emitted radiation; and   second film interposed between adjacent layers of said record dielectric layers to absorb said heat energy and to convert said absorbed heat energy to said emitted radiation.   
     
     
       2. A transducer according to claim 1 in which said first and second films have sheet resistance equal to half the electromagnetic impedance of free space for said electromagnetic radiation and said emitted radiation, respectively. 
     
     
       3. A transducer according to claim 2 whereby said electromagnetic radiation is comprised of at least one radiation from the group consisting of infrared light, visible light, and ultraviolet light, and said emitted radiation is infrared. 
     
     
       4. A transducer according to claim 3 whereby said electromagnetic radiation is transmitted to said first dielectric layers by total internal reflection. 
     
     
       5. A transducer according to claim 4 whereby said first dielectric layers are two dielectric layers. 
     
     
       6. A transducer according to claim 5 whereby said first film is a metal film. 
     
     
       7. A transducer according to claim 6 whereby said second dielectric layers are two dielectric layers. 
     
     
       8. A transducer according to claim 7 whereby said second film is a metal film. 
     
     
       9. A scene projector comprising: a plurality of waveguides to transmit electromagnetic radiation, said plurality of waveguides having a separation between one another; and   a plurality of transducers each disposed on an end of a separate one of said plurality of waveguides to absorb said electromagnetic radiation, to convert said absorbed radiation into heat energy, and to emit radiation having longer wavelengths than said electromagnetic radiation, each said transducer comprising:   first dielectric layer to receive electromagnetic radiation, each layer having thickness equal to an odd-numbered multiple of quarter wavelengths of said electromagnetic radiation;   a reflector adjacent said layers to reflect portions of said electromagnetic radiation to said layers;   first film interposed between adjacent dielectric layers to absorb said received and said reflected electromagnetic radiation and to convert said absorbed electromagnetic radiation to heat energy;   second dielectric layers adjacent said reflector to receive said heat energy, each layer of said second dielectric layers having thickness equal to an odd-numbered multiple of quarter wavelengths of desired emitted radiation; and   second film interposed between adjacent layers of said record dielectric layers to absorb said heat energy and to convert said absorbed heat energy to said emitted radiation.   
     
     
       10. A transducer according to claim 9 whereby said plurality of waveguides are optical fibers that transmit said electromagnetic radiation by total internal reflection, and said emitted radiation is IR. 
     
     
       11. A transducer according to claim 10 whereby said first dielectric layers are two dielectric layers. 
     
     
       12. A transducer according to claim 11 whereby said first film is a metal film. 
     
     
       13. A transducer according to claim 12 whereby said second dielectric layers are two dielectric layers. 
     
     
       14. A transducer according to claim 13 whereby said second film is a metal film.