Optical electromagnetic radiation detector

• US 4,533,829 A
• Filed: 07/07/1983
• Issued: 08/06/1985
• Est. Priority Date: 07/07/1983
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Ludman, Jacques E., Miceli, William J.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Brophy, J. Jon
• Application Number:
  US06/511,592
• Time in Patent Office: 761 Days
• Field of Search: 250/231 R, 250/227, 356/352, 356/345, 324/96, 324/95, 324/72, 455/612
• US Class Current: 250/227.27
• CPC Class Codes: G01J 5/10 using electric radiation detectors
• CPC Class Codes: G01R 29/0885 using optical probes, e.g. electro-optical, luminescent, glow discharge, or optical interferometers
• CPC Class Codes: G02F 1/03 based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect G02F1/061 takes precedence
• CPC Class Codes: G02F 1/213 Fabry-Perot type

Abstract

An optical electromagnetic radiation detector having a probe for receiving nearby electromagnetic radiation. The probe includes a loop antenna connected to a pair of transparent electrodes deposited on the end surfaces of an electro-optic Fabry-Perot interferometer. When the loop antenna picks up the presence of electromagnetic radiation, a voltage will be developed across the crystal of the electro-optic Fabry-Perot interferometer thereby changing the optical length of the interferometer. A beam of light from a remote location is transmitted through an optical fiber onto the Fabry-Perot interferometer. The change in optical length of the Fabry-Perot interferometer alters the intensity of the beam of light as it is reflected from the Fabry-Perot interferometer back through the optical fiber to the remote location. A beamsplitter directs this reflected beam of light onto an intensity detector in order to provide an output indicative of the variations in intensity. The variations in intensity are directly related to the strength of the electromagnetic radiation received by the loop antenna.

Claims

1. An optical electromagnetic radiation detector comprising:

an electro-optic Fabry-Perot interferometer positioned at a first location, said interferometer being made up of an electro-optic material having a pair of opposed surfaces and a pair of transparent electrodes secured to said electro-optic material;

means electrically connected to said electrodes for receiving nearby electromagnetic radiation and causing a voltage to be developed across said electro-optic material, said voltage altering the effective length of said electro-optic material thereby changing the resonant condition of said electro-optic Fabry-Perot interferometer;

means positioned at a second location for providing a monochromatic beam of light;

means having one end thereof optically aligned with said monochromatic beam of light for transmitting said beam of light out the other end thereof to said Fabry-Perot interferometer, said surfaces of said Fabry-Perot interferometer reflecting said beam of light back into said other end of said transmitting means;

means adjacent said one end of said transmitting means for receiving said reflected beam of light and directing said reflected beam of light in a predetermined direction away from said light providing means; and

means optically aligned with said light receiving and directing means for receiving said reflected beam of light therefrom and detecting any variations in the intensity in said reflected beam of light;

whereby said variations in said intensity of said reflected beam of light is directly related to the strength of said electromagnetic radiation received by said electromagnetic radiation receiving means.

2. An optical electromagnetic radiation detector as defined in claim 1 wherein said electro-optic Fabry-Perot interferometer and said means for receiving said electromagnetic radiation are contained within a housing in order to form a compact probe.

3. An optical electromagnetic radiation detector as defined in claim 2 wherein said means for transmitting said beam of light comprises an optical fiber.

4. An optical electromagnetic radiation detector as defined in claim 3 wherein said probe housing further includes means for coupling said light beam emanating from said other end of said optical fiber into said Fabry-Perot interferometer.

5. An optical electromagnetic radiation detector as defined in claim 4 wherein said means for receiving said nearby electromagnetic radiation comprises a loop antenna.

6. An optical electromagnetic radiation detector as defined in claim 5 wherein said means for providing said beam of light comprises a laser.

7. An optical electromagnetic radiation detector as defined in claim 6 wherein said means for directing said reflected beam of light comprises a beamsplitter.

8. An optical electromagnetic radiation detector as defined in claim 7 wherein said detecting means comprises an avalanche photodiode.

9. An optical electromagnetic radiation detector as defined in claim 1 wherein said means for transmitting said beam of light comprises an optical fiber.

10. An optical electromagnetic radiation detector as defined in claim 9 wherein said means for providing said beam of light comprises a laser.