Microwave receiver front-end assembly and array

• US 7,835,600 B1
• Filed: 07/18/2008
• Issued: 11/16/2010
• Est. Priority Date: 07/18/2008
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Geary, Kevin, Sievenpiper, Daniel F., Yap, Daniel, Colburn, Joseph S., Ng, Willie W., Schaffner, James H., Gregoire, Daniel J.
• Primary Examiner(s): Peace; Rhonda S
• Application Number:
  US12/176,071
• Time in Patent Office: 851 Days
• Field of Search: 385 1- 10, 385/12, 385/37, 385/43
• US Class Current: 385/12
• CPC Class Codes: G01R 29/0885 using optical probes, e.g. electro-optical, luminescent, glow discharge, or optical interferometers
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/213 Fabry-Perot type
• CPC Class Codes: G02F 1/2255 controlled by a high-frequency electromagnetic component in an electric waveguide structure
• CPC Class Codes: G02F 2201/307 Reflective grating, i.e. Bragg grating
• CPC Class Codes: H01Q 13/02 Waveguide horns
• CPC Class Codes: H01Q 3/2676 Optically controlled phased array

Abstract

A method of and apparatus for modulating an optical carrier by an incident electromagnetic field. The electromagnetic field propagates in a dielectric-filled transverse electromagnetic waveguide, At least one slice of an electro-optic material is disposed in the dielectric-filled transverse electromagnetic waveguide, the electro-optic material in the dielectric-filled transverse electromagnetic waveguide having at least one optical waveguide therein which has at least a major portion thereof guiding light in a direction orthogonal with respect to a direction in which the dielectric-filled transverse electromagnetic waveguide guides the incident electromagnetic field. Light is caused to propagate in the at least one optical waveguide in the at least one slice of an electro-optic material in the dielectric-filled transverse electromagnetic waveguide for modulation by the incident electromagnetic field.

Claims

1. A receiver front-end assembly comprising:

a. a metal-bounded dielectric-filled transverse electromagnetic waveguide for guiding a propagating electromagnetic field through said transverse electromagnetic waveguide, said transverse electromagnetic waveguide having two opposing metal surfaces,

b. an electromagnetic field concentrating antenna for coupling incident electromagnetic radiation into said transverse electromagnetic waveguide,

c. at least one slice of an electro-optic material embedded in the metal-bounded dielectric-filled transverse electromagnetic waveguide, the electro-optic material embedded in the metal-bounded dielectric-filled transverse electromagnetic waveguide having at least one optical waveguide having at least a major portion thereof guiding light in a direction orthogonal with respect to a direction in which the metal-bounded dielectric-filled transverse electromagnetic waveguide guides an electromagnetic field propagating in said transverse electromagnetic waveguide; and

d. at least one integrated electro-optic waveguide modulator disposed on or in the at least one slice of electro-optic material, said modulator including at least a portion of said at least one optical waveguide, a portion of said two opposing metal surfaces of said metal-bounded dielectric-filled transverse electromagnetic waveguide serving as driving electrodes for said modulator.

2. The receiver front-end assembly of claim 1 in combination with an RF-photonic link comprising:

a. at least one laser light source,

b. light guiding means for coupling laser light from said at least one laser light source to the at least one integrated electro-optic waveguide modulator for producing modulated light thereby;

c. at least one photodetector,

d. light guiding means for coupling the modulated laser light from the at least one integrated electro-optic waveguide modulator to the at least one photodetector.

3. The receiver front-end assembly of claim 2 wherein the at least one laser light source and the at least one photodetector are disposed in an electromagnetic-radiation tolerant enclosure so that the electromagnetic field concentrating antenna, the metal-bounded dielectric-filled transverse electromagnetic waveguide and the at least one integrated electro-optic waveguide modulator may be subjected to environmental electromagnetic fields while protecting from said environmental electromagnetic fields the at least one laser light source and the at least one photodetector disposed in the electromagnetic radiation-tolerant vessel.

4. The receiver front-end assembly of claim 3 wherein the electromagnetic-radiation tolerant enclosure has openings for passing light through from the outside of the enclosure to the inside of the enclosure, said openings having a diameter that is smaller than 0.25 mm.

5. The receiver front-end assembly of claim 1 wherein the electromagnetic field concentrating antenna is a transverse electromagnetic horn antenna having a pair of opposing electrically conductive surfaces forming a portion of a horn of said horn antenna, the metal-bounded dielectric-filled transverse electromagnetic waveguide and transverse electromagnetic horn antenna serving as an incident electromagnetic field concentrator and wherein the metal-bounded dielectric-filled transverse electromagnetic waveguide has metal surfaces ohmically coupled to the pair of opposing electrically conductive surfaces of said horn antenna for serving as driving electrodes of the at least one integrated electro-optic waveguide modulator.

6. The receiver front-end assembly of claim 5 wherein the electromagnetic field concentrating horn antenna has a square aperture at an inlet thereof, the square aperture having four sides each of which has a length equal to at most one-half of the wavelength of a frequency of an electromagnetic signal to be sensed by the front-end assembly.

7. The receiver front-end assembly of claim 5 wherein the horn antenna is filled with a dielectric material having the same dielectric constant as the dielectric of the dielectric-filled transverse electromagnetic waveguide and wherein at least one dielectric matching layer is disposed at the inlet of said horn antenna.

8. The receiver front-end assembly of claim 5 wherein the horn antenna is filled with a dielectric material having a different dielectric constant than the dielectric of the dielectric-filled transverse electromagnetic waveguide and wherein at least one dielectric matching layer is disposed between the dielectric of the horn antenna and the dielectric of the dielectric-filled transverse electromagnetic waveguide.

9. The receiver front-end assembly of claim 1 wherein the metal-bounded dielectric-filled transverse electromagnetic waveguide is rectangular in cross section with metal disposed on two opposing surfaces thereof and having two opposing surfaces free of metal to provide access for coupling optical fibers to the at least one integrated electro-optic waveguide modulator disposed on or in the at least one slice of electro-optic material in said metal-bounded dielectric-filled transverse electromagnetic waveguide.

10. The receiver front-end assembly of claim 1 wherein the at least one integrated electro-optic waveguide modulator disposed on or in the at least one slice of electro-optic material includes a Bragg grating.

11. The receiver front-end assembly of claim 1 wherein the at least one integrated electro-optic waveguide modulator disposed on or in the at least one slice of electro-optic material includes a Fabry-Perot cavity.

12. The receiver front-end assembly of claim 1 wherein the at least one integrated electro-optic waveguide modulator disposed on or in the at least one slice of electro-optic material includes an electro-optic phase modulator.

13. The receiver front-end assembly of claim 1 wherein the electromagnetic field concentrating antenna is a non-TEM horn antenna.

14. The receiver front-end assembly of claim 1 wherein the electromagnetic field concentrating antenna is a dish antenna.

15. The receiver front-end assembly of claim 1 wherein the electromagnetic field concentrating antenna is a dielectric rod antenna.

16. The receiver front-end assembly of claim 1 wherein the at least one integrated electro-optic waveguide modulator comprises a plurality of integrated electro-optic waveguide modulators disposed on or in the at least one slice of electro-optic material in said metal-bounded dielectric-filled transverse electromagnetic waveguide, said modulators being sensitive to different frequency ranges of electromagnetic radiation.

17. The receiver front-end assembly of claim 16 wherein a width of said transverse electromagnetic waveguide, on sides thereof having said two opposing metal surfaces, is different for at least two different positions along a length of said transverse electromagnetic waveguide, a first of said plurality of integrated electro-optic modulators being located at a first position in said transverse electromagnetic waveguide, said waveguide having a first width at said first position, and a second of said plurality of integrated electro-optic modulators being located at a second position in said transverse electromagnetic waveguide, said waveguide having a second width at said second position.

18. The receiver front-end assembly of claim 1 comprising a two dimensional array of said metal-bounded dielectric-filled transverse electromagnetic waveguides and associated electromagnetic field concentrating antennas for coupling incident electromagnetic radiation upon said array into said transverse electromagnetic waveguides.

19. A method of sensing incident electro-magnetic radiation, said method comprising:

a. providing at least one sensor head in which the incident radiation passes through or is reflected from said at least one sensor head;

b. passively sensing the incident radiation with an electro-optic material disposed in a RF waveguide propagating the incident radiation, and producing, according to an electric field component of said propagating radiation, modulation of light,

c. providing a remote enclosure for housing electronic and optical elements associated with said at least one sensor head, the electronic and optical elements including at least one laser for supplying light to said sensor head and at least one photodetector for converting modulated light from said sensor head to an electrical signal,

d. providing at least one optical fiber for communicating signals between (i) said electronic and optical elements in said remote enclosure and (ii) said at least one sensor head, wherein said signals communicating between (i) said electronic and optical elements and (ii) said at least one sensor head over said at least one optical fiber constitute the only signals communicating between (i) said electronic and optical elements in said remote enclosure and (ii) said at least one sensor head.

20. The method of claim 19 further including:

a. disposing multiple optoelectronic modulators into a single transverse electromagnetic waveguide disposed in said at least one sensor head;

b. supplying light from said at least one laser to said multiple optoelectronic modulators via said at least one optical fiber and supplying modulated light from said multiple optoelectronic modulators to said at least one photodetector via said at least one fiber; and

c. locating a first optoelectronic modulator of said multiple optoelectronic modulators in a first portion of said single transverse electromagnetic waveguide and locating a second optoelectronic modulator in a second portion of said single transverse electromagnetic waveguide.

21. The method of claim 19 further including disposing at least one optoelectronic modulator on or in at least one slice of electro-optic material in said waveguide, said at least one modulator being disposed in said RF waveguide and having at least one optical waveguide therein with at least a major portion of said at least one optical waveguide guiding light in a direction orthogonal with respect to a direction in which the RF waveguide guides the incident radiation propagating in said RF waveguide.

22. The method of claim 19 wherein said at least one sensor head causes negligible absorption of the incident radiation.

23. A method of modulating an optical carrier by an incident electromagnetic field comprising the steps of:

a. coupling the incident electromagnetic field into at least one transverse electromagnetic waveguide,

b. propagating the electromagnetic field through said at least one transverse electromagnetic waveguide, each of said at least one transverse electromagnetic waveguide having two opposing metal surfaces,

c. disposing at least one modulator on or in at least one slice of an electro-optic material in each of said at least one transverse electromagnetic waveguide, said at least one modulator being disposed in the transverse electromagnetic waveguide and having at least one optical waveguide therein with at least a major portion of said at least one optical waveguide guiding light in a direction orthogonal with respect to a direction in which the transverse electromagnetic waveguide guides the incident electromagnetic field propagating in said transverse electromagnetic waveguide; and

d. applying light to said at least one optical waveguide in the at least one modulator, a portion of said two opposing metal surfaces of said at least one transverse electromagnetic waveguide in which said at least one modulator is disposed serving as driving electrodes for said at least one modulator.

24. The method of claim 23 further including:

a. providing a source of light remote from said at least modulator,

b. guiding light from said source to the at least one modulator,

c. providing at least one photodetector, and

d. guiding light from the at least one modulator to the at least one photodetector.

25. The method of claim 23 further including:

guiding light, by means of an optical waveguide or optical fiber, from a first modulator disposed in a first transverse electromagnetic waveguide of said at least one transverse electromagnetic waveguide to a second modulator disposed in a second transverse electromagnetic waveguide of said at least one transverse electromagnetic waveguide.

26. The method of claim 25 wherein:

a. said electromagnetic field propagating in said first transverse electromagnetic waveguide arrives at said first modulator after a first delay time,

b. said electromagnetic field propagating in said second transverse electromagnetic waveguide arrives at said second modulator after a second delay time,

c. the time difference between said first delay time and said second delay time being equal to the time taken for light to propagate through said first modulator and through said optical waveguide or optical fiber means for guiding light from said first modulator to said second modulator.