FREQUENCY SELECTIVE MMW SOURCE

• US 20090016729A1
• Filed: 07/06/2007
• Published: 01/15/2009
• Est. Priority Date: 11/13/2006
• Status: Active Grant

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Optimer Photonics, Inc (Battelle Memorial Institute)
• Inventors: Nippa, David W., Ridgway, Richard
• Granted Patent: US 7,783,199 B2
• Time in Patent Office: Days
• US Class Current: 398/115
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 7/03 Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
• CPC Class Codes: H04B 2210/006 Devices for generating or processing an RF signal by optical means

Abstract

The present invention relates to the design and operation of a frequency selective electrooptic source. In accordance with one embodiment of the present invention, the electrooptic source comprises an optical signal generator, optical circuitry, and at least one optical/electrical converter wherein the optical signal generator comprises a plurality of optical outputs characterized by distinct output frequencies and the optical circuitry is configured to permit the selection and combination of different ones of the distinct-frequency optical outputs to generate a modulated optical signal, which is converted to a millimeter or sub-millimeter wave. Additional embodiments are disclosed and claimed.

Claims

1. An electrooptic source comprising an optical signal generator, optical circuitry, and at least one optical/electrical converter wherein the structure of the source is such that at least the following conditions apply:

the optical signal generator comprises a plurality of optical outputs characterized by distinct output frequencies;

the optical circuitry is configured to permit the selection and combination of different ones of the distinct-frequency optical outputs of the optical signal generator to generate a modulated optical signal characterized by a modulation frequency of at least about 30 GHz;

the optical circuitry is further configured to direct the modulated optical signal to at least one optical/electrical converter; and

the optical/electrical converter is configured to convert the modulated optical signal to a millimeter or sub-millimeter wave.

2. An electrooptic source as claimed in claim 1 wherein:

the optical signal generator comprises an electrooptic region modulated by a drive signal at a frequency greater than about 1 GHz; and

the optical signal generator is configured such that the distinct frequencies characterizing the optical outputs of the optical signal generator vary as a function of the frequency of the drive signal.

3. An electrooptic source as claimed in claim 1 further comprising a programmable controller operatively coupled to the optical circuitry, wherein the controller is programmed to cause the optical circuitry to select and combine different ones of the distinct-frequency optical outputs of the optical signal generator to generate a frequency-scanned modulated optical signal.

4. An electrooptic source as claimed in claim 1 further comprising a programmable controller operatively coupled to an electrooptic region of the optical signal generator, wherein:

the electrooptic region is modulated by a drive signal at a frequency greater than about 1 GHz;

the optical signal generator is configured such that the distinct frequencies characterizing the optical outputs of the optical signal generator vary as a function of the frequency of the drive signal; and

the controller is programmed to vary the drive frequency to generate a frequency-scanned modulated optical signal.

5. An electrooptic source as claimed in claim 1 further comprising a programmable controller operatively coupled to the optical circuitry and an electrooptic region of the optical signal generator, wherein:

the electrooptic region is modulated by a drive signal at a frequency greater than about 1 GHz;

the optical signal generator is configured such that the distinct frequencies characterizing the optical outputs of the optical signal generator vary as a function of the frequency of the drive signal;

the controller is programmed to vary the drive frequency and cause the optical circuitry to select and combine different ones of the distinct-frequency optical outputs of the optical signal generator to generate a frequency-scanned modulated optical signal.

6. A system as claimed in claim 1 wherein the optical circuitry is configured to direct different combinations of the distinct-frequency optical outputs to a common optical/electrical converter.

7. A system as claimed in claim 1 wherein the optical circuitry is configured to direct different combinations of the distinct-frequency optical outputs to plurality of different optical/electrical converters.

8. A system as claimed in claim 1 wherein the optical circuitry is configured to encode the modulated optical signal prior to direction to the optical/electrical converter.

9. A system as claimed in claim 1 wherein the optical signal generator comprises an electrooptic sideband generator and an optical filter.

10. A system as claimed in claim 9 wherein:

the electrooptic sideband generator is configured to generate frequency sidebands about a carrier frequency of an input optical signal; and

the optical filter is configured to discriminate between the frequency sidebands and the carrier frequency.

11. A system as claimed in claim 10 wherein the optical signal generator further comprises optical circuitry configured to direct particular sidebands of interest to an optical output in the form of a millimeter wave optical signal.

12. A system as claimed in claim 9 wherein:

the sideband generator comprises a phase modulator comprising an optical waveguide and a modulation controller configured to drive the sideband generator at a control voltage substantially larger than V_π

to generate frequency sidebands about a carrier frequency of the optical signal, where V_π

represents the voltage at which a π

phase shift is induced in the optical waveguide; and

the optical filter is configured to discriminate between the frequency sidebands and the carrier frequency such that sidebands of interest can be directed to the optical output of the optical signal generator.

13. A system as claimed in claim 9 wherein:

the sideband generator is formed over a device substrate and is configured to generate frequency sidebands about a carrier frequency of the optical signal; and

the optical filter is formed over the device substrate and is configured to discriminate between the frequency sidebands and the carrier frequency such that sidebands of interest can be directed to the optical output.

14. A system as claimed in claim 9 wherein the electrooptic sideband generator comprises an electrooptic interferometer and the optical filter comprises an arrayed waveguide grating.

15. A system as claimed in claim 14 wherein the optical circuitry is configured to combine selected optical outputs of the arrayed waveguide grating to create the modulated optical signal.

16. An electrooptic source as claimed in claim 1 wherein the optical signal generator comprises a tunable laser.

17. An electrooptic source as claimed in claim 16 wherein the optical signal generator is configured such that the distinct frequencies characterizing the optical outputs of the optical signal generator vary as a function of the operating wavelength of the tunable laser.

19. An electrooptic source as claimed in claim 1 further comprising a programmable controller operatively coupled to the electrooptic region of the optical signal generator, wherein the controller is programmed to vary the frequency of the drive signal modulating the electrooptic region of the optical signal generator.

20. An electrooptic source as claimed in claim 1 further comprising a tunable laser optically coupled to the electrooptic region.

18. An electrooptic source comprising an optical signal generator, optical circuitry, and at least one optical/electrical converter wherein the structure of the source is such that at least the following conditions apply:

the optical signal generator comprises a plurality of optical outputs characterized by distinct output frequencies;

the optical signal generator comprises an electrooptic region modulated by a drive signal at a frequency greater than about 1 GHz;

the optical signal generator is configured such that the distinct frequencies characterizing the optical outputs of the optical signal generator vary as a function of the frequency of the drive signal;

the optical circuitry is further configured to direct the modulated optical signal to at least one optical/electrical converter; and

the optical/electrical converter is configured to convert the modulated optical signal to a millimeter or sub-millimeter wave.