APPARATUS AND PROCESSES FOR DETECTION, GENERATION AND FREQUENCY MEASUREMENTS OF ELECTRO-MAGNETIC RADIATION IN THE INFRARED AND VISIBLE DOMAIN

• US 3,755,678 A
• Filed: 08/10/1970
• Issued: 08/28/1973
• Est. Priority Date: 08/10/1970
• Status: Expired due to Term

• Current Assignee: Ali Javan
• Original Assignee: Ali Javan
• Inventors: Javan, Ali
• Primary Examiner(s): Stolwein, Walter
• Application Number:
  US05/062,380
• Time in Patent Office: 1,114 Days
• Field of Search: 250/211,211J,212,83.3H,22R 317/235N,234P 324/79
• US Class Current: 257/41
• CPC Class Codes: G02F 2/002 using optical mixing

Abstract

A metal to metal point contact diode with an extremely fast response comprising a metal base and an extremely thin metal wire, a cat whisker, with an end point about the order of a thousand angstroms (0.1 micron) or less in diameter at its junction with the diode'"'"''"'"'s base. Detection of low power radiation is accomplished by detecting a voltage across the diode when incident radiation impinges on the cat whisker. Alternatively, the weak signal to be detected is coupled to the diode, together with a strong laser radiation at a frequency in the vicinity of the weak signal to be detected, thereby developing an alternating voltage signal at the difference frequency of the laser and the weak signal. This superheterodyne process is capable of detecting infrared signals below 10 15 watts. Frequency measuring is accomplished by hesterodyning an induced current in the whisker with the unknown frequency with a harmonic of a known lower frequency and a known microwave difference frequency to produce a strong beat note. The unknown frequency to be measured can be determined from the known lower frequency and the known microwave difference frequency. Generating radiation in the infrared and visible region is accomplished by subjecting the diode to an incident laser radiation. The cat whisker emits radiation at integral multiples of the laser frequency.

Claims

1. A method of producing an electrical output from visible radiation or infrared radiation of a wavelength less than about 10 microns comprising:

providing an antenna terminating at a metal-to-metal diode junction;

said antenna consisting of a conductor of effective cross dimension of the order of said radiation;

said diode junction having;

an effective diameter of the order of or less than 0.1 micron and a non-linear characteristic, with a resultant speed of response faster than the frequency of said radiation;

directing said radiation upon said antenna to induce current therein of the frequency of said radiation;

conducting said alternating current to said diode junction from said antenna and in response thereto developing an alternating voltage across said diode junction of the frequency of said radiation and alternating current through said junction having a non-linear relation to said voltage; and

deriving from said diode junction an electrical output dependent upon but differing from said alternating voltage.

2. The method of claim 1 wherein said electrical output is obtained from induced alternating current of the frequency of said radiation rectified by said diode junction.

3. The method of claim 2 including detecting a D.C. voltage resulting from said rectification.

4. The method of claim 1 wherein said radiation directed upon said antenna is modulated and said electrical output is obtained from said modulation appearing across said diode junction.

5. The method of claim 1 including mixing in said junction said alternating voltage and an alternating voltage of a different frequency, and deriving from said junction an electrical output which is the result of such mixing, a function of both of said alternating voltages.

6. A method of responding to weak visible radiation or infrared radiation of a wave length less than 10 microns, employing the method of claim 5 including directing upon said antenna said weak radiation and relatively strong radiation of known frequency in the vicinity of the frequency of said weak radiation, mixing in said diode junction alternating currents induced by said radiations and deriving said electrical output from the result of such mixing.

7. The method of claim 6 wherein said electrical output is derived as a D.C. voltage resulting from rectification by said diode junction of a frequency resulting from said mixing.

8. The method of claim 6 wherein said weak signal is modulated and said electrical effect is obtained from modulation occurring across said diode junction in the difference frequency produced by said mixing.

9. The method of claim 8 including applying a signal to the diode junction with a frequency near to said difference frequency, and obtaining said effect from the result of such mixing.

10. The method of claim 1 wherein said antenna is of wire form, an end of which terminates at said diode junction, and said radiation is directed through a focusing means upon said antenna near said junction.

11. The method of claim 1 including focusing said radiation upon said antenna with the spot diameter of the focused radiation at its intersection with the antenna being of the order of several wave lengths of said radiation.

12. The method of claim 1 wherein said diode junction is formed between the end of a thin wire antenna and a metal conductor.

13. The method of claim 1 wherein said diode junction is provided between a tungsten antenna and a nickel conductor.

14. An optical rectification system for producing a rectified electrical output from visible radiation or infrared radiation of a wavelength less than about 10 microns comprising an antenna terminating at a metal-to-metal diode junction;

said antenna consisting of a conductor of effective cross dimension of the order of said radiation;

said diode junction having;

an effective diameter of the order of or less than 0.1 micron and a non-linear characteristic, with a resultant speed of response faster than the frequency of said radiation;

means defining an optical path for directing said radiation upon said antenna to induce current therein of the frequency of said radiation;

said antenna conducting said alternating current to said diode junction from said antenna whereby through the interaction of said current and said diode juction there is produced an alternating voltage across said diode junction of the frequency of said radiation and an alternating current through said junction having a non-linear relation to said voltage; and

an output connection for deriving from said diode junction an electrical output obtained from induced alternating current of frequency of said radiation rectified by said diode junction.

15. A frequency multiplier chain including a frequency of visible radiation or infrared radiation of a wavelength less than about 10 microns comprising an antenna terminating at a metal-to-metal diode junction;

said antenna consisting of a conductor of effective cross dimension of the order of said radiation;

said diode junction having;

an effective diameter of the order of or less than 0.1 micron and a non-linear characteristic, with a resultant speed of response faster than the frequency of said radiation;

means defining an optical path for directing said radiation upon said antenna to induce current therein of the frequency of said radiation;

said antenna conducting said alternating current to said diode junction whereby through the interaction of said current and said diode junction there is produced an alternating voltage across said diode junction of the frequency of said radiation and an alternating current through said junction having a non-linear relation to said voltage, means for producing another alternating voltage across and related current through said diode junction and output means for deriving a signal derived from the result of mixing of frequencies related to said two currents in said diode junction.

16. A tunable detector for weak optical radiation useful for detection of spontaneous emission lines as from a gas discharge or for detection of spectral lines from outer space comprising:

an antenna terminating at a metal-to-metal diode junction; and

optical element for directing said weak optical radiation upon said antenna near said diode junction;

a laser for producing a beam of radiation of known frequency and stronger power than said weak optical radiation, said radiation being in the range of visible and infrared of less than about 10 micron wave length, a second optical element for directing said laser beam upon said antenna near said diode junction; and

a tunable source of lower frequency arranged to produce a signal across said diode junction;

said antenna having an effective diameter of the order of or less than the wave lengths of radiation directed thereupon to induce therein currents of the same frequencies;

said diode junction having a diameter of the order of or less than 0.1 micron and having a non-linear characteristic with a speed of response faster than the frequencies of said opical radiation and said laser beam;

said optical elements arranged to couple said weak radiation and laser beam to said diode junction via said antenna whereby said diode junction is effective to mix alternating current signals based upon said radiating laser and lower frequency source;

an output connection from said diode junction and an indicator responsive to said output to indicate the presence of beats between a mixture of signals based upon said optical radiation, laser beam and lower frequency source, said detector being tunable for optical radiation of differing frequency by varying the frequency of said lower frequency source.