Wideband microwave and millimeter wave filters using photonic spectral filtering

• US 20090297155A1
• Filed: 08/09/2007
• Published: 12/03/2009
• Est. Priority Date: 08/11/2006
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (Purdue University)
• Original Assignee: Purdue Research Foundation (Purdue University)
• Inventors: Weiner, Andrew M., Xiao, Shijun
• Granted Patent: US 7,974,534 B2
• Time in Patent Office: Days
• US Class Current: 398/115
• CPC Class Codes: G02F 1/2255 controlled by a high-frequency electromagnetic component in an electric waveguide structure
• CPC Class Codes: G02F 2203/055 wavelength filtering
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04B 10/00 Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
• CPC Class Codes: H04B 2210/006 Devices for generating or processing an RF signal by optical means

Abstract

An apparatus and method is disclosed for producing and filtering optical and electrical waveforms. The apparatus includes an electro-optical modulator, an optical filter capable of modulating at least two spectral regions within the bandwidth of the electrical waveform, and an optical-to-electrical converter. The optical filter includes a spatial dispersion means, a spatial modulating means having the capability to substantially independently modulate a characteristic of each of a pair of optical spatial elements.

Claims

1. An apparatus for filtering a waveform, comprising:

an electro-optic modulator adapted to accept a first optical signal and an electrical modulating signal;

a optical filter adapted to accept an output of the modulator and to modify at least one of an amplitude or phase of the modulator output within a bandwidth of the electrical signal; and

an opto-electronic converter.

2. The apparatus of claim 1, wherein the first optical signal is present at the opto-electronic converter.

3. The apparatus of claim 1, wherein the opto-electric converter is a photodiode.

4. The apparatus of claim 1, wherein the first optical signal is provided by a laser.

5. The apparatus of claim 4, wherein the laser is one of a fiber laser or a semiconductor laser device.

6. The apparatus of claim 1, wherein the first optical signal is a constant amplitude coherent signal.

7. The apparatus of claim 1, wherein a second optical signal is provided at the opto-electrical detector.

8. The apparatus of claim 7, wherein the amplitude of the second optical signal results in substantially coherent detection of the output of the optical filter.

9. The apparatus of claim 7, wherein a wavelength of the second optical signal is different from a wavelength of the first optical signal.

10. The apparatus of claim 1, wherein the modulating signal is a substantially constant amplitude microwave signal.

11. The apparatus of claim 1, wherein the modulating signal is a pulsed microwave signal.

12. The apparatus of claim 1, wherein the optical filter is a programmable optical filter.

13. The apparatus of claim 12, wherein the optical filter is programmable in at least one of wavelength or time.

14. The apparatus of claim 1, wherein the optical filter further comprises:

a wavelength dispersive optical element; and

a spatial optical modulator.

15. The apparatus of claim 14, wherein the wavelength dispersive optical element is a diffraction grating or a virtual imaged phased array (VIPA).

16. The apparatus of claim 14, wherein the spatial optical modulator is a liquid crystal phase shifter having spatial elements, the phase shift of at least two of the elements being controllable.

17. The apparatus of claim 14, wherein the optical filter is configured as a reflective device having a mirror disposed on a side of the spatial modulator opposite from that facing the wavelength dispersive optical element.

18. The apparatus of claim 14, where the optical filter further comprises:

a virtual imaged phased array (VIPA);

wherein the spatial optical modulator is disposed at a focal plane of a light path.

36. An apparatus for transmitting electrical signals, comprising:

an optical source;

an electrical modulating signal;

an apparatus as claimed in claim 1; and

an electronic amplifier.

37. That apparatus of claim 36, further comprising an antenna.

38. An apparatus for receiving electrical signals, comprising:

an electronic amplifier;

an optical source; and

an apparatus as claimed in claim 1;

39. The apparatus of claim 38, further comprising an antenna.

19. An apparatus for producing electrical waveforms, comprising:

an electro-optical modulator configured to accept a first optical signal and an electrical signal;

an optical filter that varies at least one of the amplitude or phase of an optical output signal of the electro-optical modulator as a function of wavelength within the bandwidth of the electrical signal; and

an opto-electrical detector.

20. The apparatus of claim 19, wherein the input to the opto-electrical detector is an output signal from the optical filter and a second optical signal.

21. The apparatus of claim 19, wherein the optical filter has a wavelength resolution such that at least two spectral portions within the bandwidth of the electrical signal may be substantially independently varied.

22. The apparatus of claim 21, wherein the optical filtering is time varying.

23. The apparatus of claim 19, wherein the first optical signal is a substantially continuous wave output signal of a coherent optical source.

24. The apparatus of claim 20, where the second optical signal is a substantially continuous wave optical signal.

25. The apparatus of claim 19, wherein the first optical signal and the second optical signal are derived from a common optical signal.

26. The apparatus of claim 19, wherein the variation of the at least one of the amplitude or phase is on a wavelength scale equivalent to a spatial resolution of a spatial modulator component of the optical filter.

27. The apparatus of claim 26, wherein the variation is a function of time.

28. The apparatus of claim 19, wherein the optical filter has a wavelength resolution such that at least two optical spectral portions within the bandwidth of the electrical signal may be substantially independently varied.

29. The apparatus of claim 28, wherein an individual resolution element of a spatial modulator component of the optical filter is capable of introducing a phase shift of at least 2π

.

30. The apparatus of claim 19, wherein the opto-electrical detector performs a coherent detection of an optical signal output of the optical filter.

31. The apparatus of claim 19, wherein the opto-electrical detector performs a non-coherent detection of the optical signal output of the optical filter.

32. The apparatus of claim 19, wherein the electrical signal is a pulsed microwave signal.

33. A method of filtering an electrical signal, the method comprising:

providing an electro-optical modulator adapted to accept an optical signal and an electrical modulating signal;

optically filtering the modulated optical signal, where the optical filter characteristics are a function of wavelength within a bandwidth of the electrical modulating signal; and

detecting the filtered optical signal.

34. The method of claim 33, wherein the electrical modulating signal is time shifted by optically filtering the modulated optical signal so as to introduce an additional linear phase shift as a function of wavelength.

35. The method of claim 33, wherein the time shift is either positive or negative depending on the sign of the additional linear phase shift.

40. An apparatus for generating electrical signals, comprising;

means for modulating an optical signal with an electrical signal;

means for modifying an optical spectrum of the modulated optical signal; and

means for detecting the modified modulated optical signal.