Generating and using coherent optical radiation

Abstract

Optical radiation generation and detection using metal-to-metal diode junctions. Coherent optical radiation is generated by using an antenna connected to a metal-to-metal diode junction with non-linear current-voltage characteristics and by coupling to the junction electromagnetic radiation energy to interact with the junction, causing emission from the antenna at optical frequency absent from the input. Optical diodes are shown in the forms of a mechanically contacted cat whisker system and as single and multiple microscopic solid portions in an integrated solid mass, defining both the antenna and the junction, preferably as a deposit of solid layers upon a substrate, preferably as overlapping printed circuit line structures. Arrays of such junctions provide enhanced effects; useful arrays include Franklin-Marconi geometries, fish-bone antennas and row and column arrays. Such solid diode constructions and arrays thereof are used not only for optical radiation generation but also detection and mixing including use in an image scanner, energy converter and a broad band detector. The diodes as a radiation source are used in combination with an absorbtion cell in spectroscopic analysis, a feedback loop in a stable frequency source, and an optical frequency communicating system.

I claim: 
     
       1. A method for generating coherent optical radiation comprising providing an antenna connected to a metal-to-metal diode junction having non-linear characteristics, and coupling to said diode junction an input of electromagnetic energy sufficient to interact with said junction to cause generation of current through said junction, causing flow of said current in said antenna, and causing resultant emission of coherent radiation from said antenna, said current and radiation being of an optical frequency which is dependent upon the frequency of said input and absent from said input. 
     
     
       2. The method of claim 1 wherein said diode junction is provided by a metal cat whisker with pointed end in contact with a metal base. 
     
     
       3. The method of claim 1 wherein said diode junction is provided by solid deposits of two metal layers having a limited common area at which the metals are separated by a dielectric forming in effect a metal-to-metal junction with non-linear current-voltage characteristics. 
     
     
       4. A method as claimed in claim 1 comprising collecting said radiation of said optical frequency emitted from said antenna for direction to a station of utilization. 
     
     
       5. A method as claimed in claim 1 wherein said input comprises radiation of optical frequency coupled to said junction through said antenna. 
     
     
       6. A method as claimed in claim 1, wherein said input comprises a component frequency in the microwave range. 
     
     
       7. A method as claimed in claim 6 including varying said microwave frequency so that said emitted optical radiation has a desired frequency. 
     
     
       8. A method as claimed in claim 7, said microwave frequency being modulated by an information bearing signal, thereby causing said emitted optical radiation to be modulated by said signal. 
     
     
       9. A method as claimed in claim 1, said emitted radiation being produced by even order mixing, and including applying a d.c. biasing voltage across said junction. 
     
     
       10. A method is claimed in claim 2, said pointed end having a radius of curvature less than 50 nm. 
     
     
       11. A method as claimed in claim 2, said cat whisker having a diameter smaller than the wavelength of said emitted radiation. .[. 
     
     
       12.  Apparatus for generating coherent optical radiation comprising at least one antenna connected to a diode junction having non-linear characteristics, a source of electromagnetic energy coupled to said diode junction to interact with said junction to cause generation of a current through said junction, flow of said current through said antenna and emission of radiation from said antenna, said current and radiation being of optical frequency which is related to the frequency of the frequency of the input and absent from the input,   an optical element for collecting said radiation of said optical frequency emitted from said antenna for direction to a station for utilization..]. .[.13. Apparatus as claimed in claim 12, said source providing a component of electromagnetic energy with a frequency in the microwave range..]. .[.14. Apparatus as claimed in claim 13, further comprising means for controllably varying said microwave frequency..]. .[.15. Apparatus as claimed in claim 14, including controls for adjusting said microwave   
     
     
        frequency so that said emitted radiation has a desired frequency..]. 16. .[.Apparatus as claimed in claim 14,.]. .Iadd.Apparatus for generating coherent optical radiation comprising at least one antenna connected to a diode junction having non-linear characteristics, a source of electromagnetic energy coupled to said diode junction to interact with said junction to cause generation of a current through said junction, flow of said current through said antenna and emission of radiation from said antenna, said current and radiation being of optical frequency which is related to the frequency of the input and absent from the input, said source providing a component of electromagnetic energy with a frequency in the microwave range,   an optical element for collecting said radiation of said optical frequency emitted from said antenna for direction to a station for utilization, and   means for controllably varying said microwave frequency, .Iaddend.including means for modulating said microwave frequency by an information bearing   
     
     
        signal, whereby said emitted radiation is modulated by said signal. 17. .[.Apparatus as claimed in claim 12,.]. .Iadd.Apparatus for generating coherent optical radiation comprising at least one antenna connected to a diode junction having non-linear characteristics, a source of electromagnetic energy coupled to said diode junction to interact with said junction to cause generation of a current through said junction, flow of said current through said antenna and emission of radiation from said antenna, said current and radiation being of optical frequency which is related to the frequency of the input and absent from the input,   an optical element for collecting said radiation of said optical frequency emitted from said antenna for direction to a station for utilization, .Iaddend.said diode junction including a cat whisker with a pointed end   
     
     
        contacting a base. 18. Apparatus as claimed in claim 17, said base being 
     
     
        made of nickel. 19. .[.Apparatus as claimed in claim 12,.]. .Iadd.Apparatus for generating coherent optical radiation comprising at least one antenna connected to a diode junction having non-linear characteristics, a source of electromagnetic energy coupled to said diode junction to interact with said junction to cause generation of a current through said junction, flow of said current through said antenna and emission of radiation from said antenna, said current and radiation being of optical frequency which is related to the frequency of the input and absent from the input,   an optical element for collecting said radiation of said optical frequency emitted from said antenna for direction to a station for utilization, .Iaddend.said emitted radiation being produced by even order mixing, and including a source of d.c. biasing voltage applied across said junction.   
     
     
          . Apparatus as claimed in claim 17 said pointed end having a radius of 
     
     
        curvature less than 50 nm. 21. Apparatus as claimed in claim 17, said cat whisker having a diameter smaller than the wavelength of said emitted radiation. .[.22. Apparatus as claimed in claim 15, said control for said microwave frequency including a feedback loop connected through said diode 
     
     
        to stabilize the frequency of said emitted optical radiation..]. 23. .[.Apparatus according to claim 12.]. .Iadd.Apparatus for generating coherent optical radiation comprising at least one antenna connected to a diode junction having non-linear characteristics, a source of electromagnetic energy coupled to said diode junction to interact with said junction to cause generation of a current through said junction, flow of said current through said antenna and emission of radiation from said antenna, said current and radiation being of optical frequency which is related to the frequency of the input and absent from the input, and   an optical element for collecting said radiation of said optical frequency emitted from said antenna for direction to a station for utilization,   said apparatus .Iaddend.comprising a solid substrate, a solid metal deposit thereon, a solid dielectric layer upon a portion of said metal deposit, and a second solid metal deposit on said substrate, said second metal deposit having a predetermined limited common area with said first metal deposit, the respective common portions of said metal deposits being in intimate contact with opposite sides of and separated by said dielectric layer, said dielectric layer being of limited thickness, said common region thereby defining a potential barrier producing a metal-to-metal junction with nonlinear voltage current characteristics, a portion of one of said metal deposits extending away from said common region having a width related to the wave length of said optical radiation and, forming an antenna responsive to said incident radiation to generate an alternating electrical current at the frequency of said radiation, and to conduct said   
     
     
        current to said junction. 24. The apparatus according to claim 23 wherein said dielectric layer is of the order of 1 manometer or less thickness, said metal deposits and interposed dielectric layer chosen to provide a barrier potential enabling quantum mechanical electron tunneling across the said potential barrier to predominantly determine junction impedance. 
     
     
         5. Apparatus for generating optical radiation comprising an array of devices formed on a substrate transparent to the generated radiation, each device including an antenna connected to a diode junction having non-linear current-voltage characteristics, each of said devices including an elongated deposit of a first conductive material, a dielectric layer contacting a portion of said deposit, and a deposit of a second conductive material contacting said dielectric material close to said elongated deposit, the devices in said array being disposed to give cooperative directional radiation,   a source of electromagnetic energy coupled to the junctions of said array to cause generation of currents in said junctions, flow of said currents through said antennas and emission radiation from said antennas, said currents and radiation being of optical frequency absent from inputs to the devices.