Claims
- 1. A system for measuring a terahertz frequency pulse propagating in a free-space optical path, the system comprising:
an optical streak camera; and an electro-optical modulator positioned before the optical streak camera in the free-space optical path, wherein the streak camera measures an optical intensity as a function of time.
- 2. The system of claim 1 wherein the terahertz frequency pulse is measured in a single shot.
- 3. The system of claim 1 wherein the terahertz frequency pulse comprises subpicosecond free-space electromagnetic radiation with a bandwidth in a range from 10 gigahertz to 40 terahertz.
- 4. The system of claim 1 wherein the terahertz frequency pulse modulates a probe pulse.
- 5. The system of claim 4 wherein the modulation of the probe pulse occurs as the terahertz frequency pulse and the probe pulse copropagate in the electro-optical modulator.
- 6. The system of claim 4 wherein the probe pulse is stretched relative to the terahertz frequency pulse.
- 7. The system of claim 6 wherein the probe pulse is stretched via a chirped pulse technique.
- 8. The system of claim 4 wherein the probe pulse is synchronized with the streak camera.
- 9. The system of claim 1 wherein the electro-optical modulator comprises:
an electro-optical crystal; and a polarization analyzer.
- 10. The system of claim 9, wherein the electro-optical crystal comprises one of a ZnTe crystal, a GaAs crystal, a CdTe crystal, a CdZnTe crystal, and an organic DAST crystal.
- 11. The system of claim 9 wherein the polarization analyzer converts a polarization modulation into an intensity modulation.
- 12. The system of claim 9 wherein the polarization analyzer is in a crossed-polarizer geometry.
- 13. The system of claim 1 wherein the streak camera comprises an electron tube comprising a photo cathode, an accelerating mesh, at least two electrodes, a multi-channel plate, and a phosphor screen.
- 14. The system of claim 13 wherein the streak camera further comprises a data processing device to process data from the phosphor screen.
- 15. The system of claim 14 wherein the data processing device is a CMOS.
- 16. The system of claim 14 wherein the data processing device is a charge coupled device camera.
- 17. The system of claim 1 further comprising an optical source, for providing a probe pulse and a pump pulse, and an emitter wherein the pump pulse excites the emitter to emit the terahertz frequency pulse.
- 18. The system of claim 17 wherein the optical source is a laser.
- 19. The system of claim 18 wherein the laser is a Ti:sapphire laser.
- 20. The system of claim 1 further comprising a probe pulse polarizer positioned before the electro-optical modulator in a probe pulse optical path.
- 21. The system of claim 1 further comprising a trigger to synchronize the streak camera and the probe pulse.
- 22. The system of claim 21 wherein the trigger is a PIN diode.
- 23. The system of claim 17 further comprising one or more lenses between the emitter and the electro-optical modulator.
- 24. A system for measuring a free-space terahertz frequency pulse emitted from an emitter and propagating in an optical path, the system comprising:
an optical streak camera; an optical source and related optics for providing a pump pulse to excite the emitter to emit the terahertz frequency pulse and a probe pulse to probe the terahertz frequency pulse; a probe pulse stretcher that produces a stretched probe pulse; a probe pulse polarizer that produces a polarized stretched probe pulse from the stretched probe pulse; a trigger that synchronizes the streak camera and the probe pulse; and an electro-optical modulator positioned before the optical streak camera in the optical path, the electro-optical modulator comprising an electro-optical crystal and a polarization analyzer; wherein an electric field is generated by the terahertz frequency pulse when the terahertz frequency pulse propagates through the electro-optical crystal, the electric field modulates the polarization of the polarized stretched probe pulse in the electro-optical modulator, generating a polarization modulation, wherein the polarization modulation is converted to an intensity modulation by the polarization analyzer, and the intensity modulation is measured by the streak camera.
- 25. The system of claim 24 wherein the terahertz frequency pulse comprises subpicosecond free-space electromagnetic radiation with a bandwidth in a range from 10 gigahertz to 40 terahertz.
- 26. The system of claim 24 wherein the electro-optical modulator is in a crossed-polarization geometry.
- 27. The system of claim 24 wherein an index of refraction of the electro-optical crystal changes as a function of a local electromagnetic field.
- 28. The system of claim 27 wherein the electro-optical crystal comprises one of a ZnTe crystal, a GaAs crystal, a CdTe crystal, a CdZnTe crystal, and an organic DAST crystal.
- 29. The system of claim 24 wherein the optical source is a laser and the trigger is a PIN diode.
- 30. A method for measuring terahertz frequency electromagnetic pulses as a function of time, the method comprising the steps of:
(a) providing an optical pump pulse and an optical probe pulse; (b) exciting a terahertz frequency emitter with the optical pump pulse; (c) stretching the optical probe pulse relative to the optical pump pulse; (d) polarizing the optical probe pulse; (e) modulating the probe pulse with a local electromagnetic field generated by the emitted pulse in an electro-optical modulator, the modulating resulting in a probe pulse polarization modulation; (f) converting the polarization modulation into an intensity modulation; and (g) measuring the intensity modulation as a function of time.
- 31. The method of claim 30 wherein, in step (e), an index of refraction of an electro-optical crystal within the electro-optical modulator changes as a function of the local electromagnetic field.
- 32. The method of claim 30 further comprising a step of synchronizing the optical probe pulse with a streak camera.
- 33. An apparatus for measuring a free-space frequency pulse in a time-dependent manner, said apparatus comprising:
an electro-optic crystal positioned so that the free-space frequency pulse passes therethrough, thereby changing an index of refraction of the electro-optical crystal; means for generating an optical probe signal to impinge the electro-optical crystal simultaneously with the free-space frequency pulse passing therethrough; means for determining the polarization modulation of the optical probe signal after impinging upon the electro-optical crystal; means for characterizing the free-space frequency pulse by evaluating the polarization modulation of the optical probe signal; and means for time dependent measurement of the characterization from the polarization modulation.
- 34. The apparatus of claim 33 wherein the means for characterizing includes means for determining a change in the index of refraction of the electro-optical crystal by analyzing the polarization modulation of the optical probe signal.
- 35. The apparatus of claim 33 wherein the optical probe signal comprises a polarized optical probe signal.
- 36. The apparatus of claim 33 wherein the electro-optical crystal comprises one of a ZnTe crystal, a GaAs crystal, a CdTe crystal, a CdZnTe crystal, and an organic DAST crystal.
- 37. The apparatus of claim 33 wherein the free-space frequency pulse comprises subpicosecond free-space electromagnetic radiation with a bandwidth in a range from 10 gigahertz to 40 terahertz.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority based upon U.S. Provisional Patent Application Serial No. 60/195,555, filed on Apr. 6, 2000, which is incorporated herein by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60195555 |
Apr 2000 |
US |