Photonic RF and microwave phase shifters

• US 8,089,684 B1
• Filed: 03/16/2009
• Issued: 01/03/2012
• Est. Priority Date: 03/14/2008
• Status: Active Grant

• Current Assignee: Oewaves Incorporated
• Original Assignee: Oewaves Incorporated
• Inventors: Maleki, Lute, Koonath, Prakash
• Primary Examiner(s): Hasan, Mohammed
• Application Number:
  US12/405,113
• Time in Patent Office: 1,023 Days
• Field of Search: 359/237, 359/245, 359/251, 359276-279, 359/256, 359/264, 359/239, 372/32, 250/227.11
• US Class Current: 359/279
• CPC Class Codes: G02F 1/0311 Structural association of optical elements, e.g. lenses, polarizers, phase plates, with the crystal
• CPC Class Codes: G02F 1/0338 structurally associated with a photoconductive layer or having photo-refractive properties G02F1/05 takes precedence
• CPC Class Codes: G02F 1/0356 controlled by a high-frequency electromagnetic wave component in an electric waveguide structure
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/50 Phase-only modulation
• CPC Class Codes: H03B 17/00 Generation of oscillations using radiation source and detector, e.g. with interposed variable obturator

Abstract

Techniques and devices for tuning a phase shift of an RF or microwave signal by using an optical tuning mechanism based on photonic elements.

Claims

1. A phase shifter device for shifting a phase of an oscillation signal, comprising:

a laser that produces a laser output beam at a laser carrier frequency;

an optical interferometer located in an optical path of the laser output beam to receive the laser output beam and comprising an optical splitter that splits the laser output beam into a first laser beam and a second laser beam, a first optical path that receives the first laser beam, a second optical path that receives the second laser beam, and an optical combiner where the first and second optical paths meet and terminate, the optical combiner combing the first laser beam and the second laser beam to produce a combined optical output;

an optical modulator coupled in the second optical path of the optical interferometer to cause a modulation of light in the second optical path at a modulation frequency in response to an input oscillation signal oscillating at the modulation frequency to introduce modulation sidebands at two sides of the laser carrier frequency in the second optical beam;

an optical resonator optically coupled in the second optical path between the optical modulator and the optical combiner to filter the second optical beam output by the optical modulator to transmit light at a selected modulation sideband while rejecting light outside the selected modulation sideband, including light at the laser carrier frequency and one or more other modulation sidebands;

a photodetector located to receive the combined optical output from the optical combiner of the optical interferometer and to convert the received combined optical output into an output oscillation signal whose phase is shifted relative to a phase of the input oscillation signal by a relative optical phase shift between the first optical path and the second optical path of the optical interferometer.

2. The device as in claim 1, comprising:

a phase shifter in the first optical path to control an amount of the relative optical phase shift between the first optical path and the second optical path of the optical interferometer.

3. The device as in claim 1, wherein:

the optical resonator is a tunable optical resonator that tunes a resonance frequency of the optical resonator to change the frequency of the output oscillation signal whose phase is shifted.

4. The device as in claim 3, wherein:

the optical resonator is electronically tuned to change the frequency of the output oscillation signal.

5. The device as in claim 3, wherein:

the optical resonator is made of an electro-optic material and is tuned by an electrical voltage applied to the electro-optic material to change the frequency of the output oscillation signal.

6. The device as in claim 3, comprising:

a mechanism to control a temperature of the optical resonator to tune the optical resonator in changing the frequency of the output oscillation signal.

7. The device as in claim 3, comprising:

a mechanism that applies and controls a pressure exerted on the optical resonator to tune the optical resonator in changing the frequency of the output oscillation signal.

8. A method for shifting a phase of an RF or microwave signal, comprising:

directing laser light at a laser carrier frequency from a laser into an optical interferometer which includes a first optical path and a second optical path that intersect to produce optical interference between light in the first and second optical paths;

applying an input RF or microwave signal at an RF or microwave frequency to perform an optical modulation on light in the second optical path to produce modulated laser light in the second optical path to produce modulation sidebands at two sides of the laser carrier frequency in the modulated laser light;

optically filtering the modulated laser light in the second optical path to produce filtered laser light having a selected modulation sideband that is away from the laser carrier frequency by the RF or microwave frequency while being free of spectral components outside the selected modulation sideband, including light at the laser carrier frequency and one or more other modulation sidebands; and

combing the filtered laser light in the second optical path and the laser light in the first optical path at a photodetector to recover the input RF or microwave signal with a phase shift that is determined a relative optical phase shift between the first optical path and the second optical path of the optical interferometer.

9. The method as in claim 8, comprising:

tuning the relative optical phase shift between the first optical path and the second optical path of the optical interferometer to change the phase shift in the recovered input RF or microwave signal at the photodetector.

10. The method as in claim 8, comprising:

tuning an optical phase delay in the first optical path to change the phase shift in the recovered input RF or microwave signal at the photodetector.

11. The method as in claim 8, comprising:

operating a phase shifter in the first optical path to change the phase shift in the recovered input RF or microwave signal at the photodetector.

12. The method as in claim 8, comprising:

using a tunable optical resonator to perform the optical filtering in the second optical path; and

tuning the tunable optical resonator to change the frequency of the recovered RF or microwave signal with the phase shift.

13. The method as in claim 8, comprising:

using an optical micro resonator that supports whispering gallery modes in the second optical path to perform the optical filtering.

14. A method for shifting a phase of an RF or microwave signal, comprising:

operating an optical modulator to modulate light of a laser beam in response to an input RF or microwave signal at an RF or microwave frequency to produce modulated light that carries the input RF or microwave signal in the optical domain;

optically processing the modulated light to produce an optical output that has an optical phase shift; and

detecting the optical output to produce an output RF or microwave signal at the RF or microwave frequency of the input RF or microwave signal with a phase shift that corresponds to the optical phase shift,

wherein;

the light of the laser beam that is modulated by the optical modulator is a first portion of the laser beam and the modulated light is the modulated first portion, and

the optical processing includes;

filtering the modulated first portion to produce a filtered first portion which carries a selected optical modulation sideband while being free of light outside the selected optical modulation sideband;

causing an optical phase shift between the filtered first portion of the laser beam and a second portion of the same laser beam; and

causing optical interference between the filtered first portion and the second portion of the same laser beam to produce the optical output.

15. The method as in claim 14, comprising:

adjusting the optical phase shift to change the phase shift in the output RF or microwave signal.

16. The method as in claim 14, comprising:

using an electrically tunable optical micro resonator to adjust a center frequency of the filtered first portion to change the RF or microwave frequency of the output RF or microwave signal.