Chirped pulse frequency-domain comb for spectroscopy

Patent metadata

Field	Value
Publication number	US-9891165-B2
Application number	US-201615255036-A
Country	US
Kind code	B2
Filing date	Sep 1, 2016
Priority date	Jun 17, 2010
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A pulse train comprising chirped pulses can be used to excite a sample, such as for spectroscopic analysis. The respective chirped pulses can include a frequency sweep to establish a first frequency-domain comb. A width of frequency-domain comb peaks can be established at least in part by a total duration of the pulse train, and a bandwidth of the first frequency-domain comb can be determined at least in part by a bandwidth of the frequency sweep of the respective chirped pulses. A free-space or enclosed sample interaction region can be used.

First claim

The claimed invention is:

1. A method, comprising:
generating a pulse train comprising phase-coherent frequency-chirped pulses of at least one of microwave, millimeter-wave, or sub-millimeter wave electromagnetic energy;
applying a time-domain window to at least one frequency-chirped pulse in the pulse train; and
exciting a sample using the pulse train.

2. The method of claim 1 , the pulse train including at least one frequency-chirped pulse within a frequency range of about 1 GHz to about 1 THz.

3. The method of claim 1 , the pulse train including at least one frequency-chirped pulse within a frequency range of about 3 THz to about 30 THz.

4. The method of claim 1 , wherein the pulse train includes unevenly spaced frequency-domain components.

5. The method of claim 1 , wherein the pulse train includes evenly spaced frequency-domain components.

6. The method of claim 1 , further comprising applying a phase shift to each frequency-chirped pulse in the pulse train, the phase shift applied to a later pulse of the pulse train being greater than the phase shift applied to an earlier pulse of the pulse train.

7. The method of claim 1 , the generating the pulse train including, for each frequency-chirped pulse of the pulse train:
generating a baseband frequency-chirped pulse;
upconverting the baseband frequency-chirped pulse to generate an upconverted frequency-chirped pulse; and
frequency multiplying the upconverted frequency-chirped pulse to produce the frequency-chirped pulse.

8. The method of claim 1 , wherein the pulse train is a first pulse train of a plurality of pulse trains, and wherein the phase-coherent frequency-chirped pulses in the first pulse train of the plurality of pulse trains have the same phase as phase-coherent frequency-chirped pulses in at least one other pulse train of the plurality of pulse trains.

9. The method of claim 1 , further comprising:
detecting, from the sample and in response to the excitation, a sample response; and
applying a pulse-shaping window to the sample response.

10. The method of claim 1 , the pulse train having a first comb peak separation, the method further comprising:
detecting, from the sample and in response to the excitation, a sample response; and
mixing the sample response with a frequency domain comb, the frequency domain comb having a second comb peak separation that is greater than the first comb peak separation.

11. An apparatus, comprising:
a signal generator configured to:
generate a pulse train comprising phase-coherent frequency-chirped pulses of at least one of microwave, millimeter-wave, or sub-millimeter wave electromagnetic energy; and
apply a time-domain window to at least one frequency-chirped pulse in the pulse train; and

an antenna operably coupled to the signal generator and configured to couple the pulse train to a sample, the pulse train exciting the sample.

12. The apparatus of claim 11 , the pulse train including at least one frequency-chirped pulse within a frequency range of about 1 GHz to about 1 THz.

13. The apparatus of claim 11 , wherein the pulse train includes unevenly spaced frequency-domain components.

14. The apparatus of claim 11 , wherein the pulse train includes evenly spaced frequency-domain components.

15. The apparatus of claim 11 , wherein the pulse train is a first pulse train of a plurality of pulse trains, and wherein the phase-coherent frequency-chirped pulses in the first pulse train of the plurality of pulse trains have the same phase as the phase-coherent frequency-chirped pulses in at least one other pulse train of the plurality of pulse trains.

16. The apparatus of claim 11 , further comprising a sample region configured to hold the sample, the sample region coupled to the antenna.

17. The apparatus of claim 11 , the signal generator including:
a waveform generator configured to generate the pulse train; and
a mixer operably coupled to the waveform generator and configured to apply the time domain window to at least one frequency-chirped pulse in the pulse train.

18. An apparatus, comprising:
a signal generator configured to:
generate a pulse train comprising phase-coherent frequency-chirped pulses of at least one of microwave, millimeter-wave, or sub-millimeter wave electromagnetic energy; and
apply a time-domain window to at least one chirped pulse in the pulse train; and

a waveguide operably coupled to the signal generator and configured to couple the pulse train to a sample, the pulse train exciting the sample.

19. The apparatus of claim 18 , the pulse train including at least one frequency-chirped pulse within a frequency range of about 1 GHz to about 1 THz.

20. The apparatus of claim 18 , wherein the pulse train includes unevenly spaced frequency-domain components.

21. The apparatus of claim 18 , wherein the pulse train includes evenly spaced frequency-domain components.

22. The apparatus of claim 18 , wherein the pulse train is a first pulse train of a plurality of pulse trains, and wherein the phase-coherent frequency-chirped pulses in the first pulse train of the plurality of pulse trains have the same phase as the phase-coherent frequency-chirped pulses in at least one other pulse train of the plurality of pulse trains.

23. The apparatus of claim 18 , further comprising a sample region configured to hold the sample, the sample region coupled to the waveguide.

24. The apparatus of claim 18 , the signal generator including:
a waveform generator configured to generate the pulse train; and
a mixer operably coupled to the waveform generator and configured to apply the time domain window to at least one frequency-chirped pulse in the pulse train.

25. A method, comprising:
generating a pulse train comprising phase-coherent frequency-chirped pulses of at least one of microwave, millimeter-wave, or sub-millimeter wave electromagnetic energy;
exciting a sample using the pulse train;
detecting, from the sample and in response to the excitation, a sample response; and
applying a pulse-shaping window to the sample response.

26. The method of claim 25 , further comprising applying a phase shift to each frequency-chirped pulse in the pulse train, the phase shift associated with a later pulse of the pulse train being greater than the phase shift associated with an earlier pulse of the pulse train.

27. The method of claim 25 , the generating the pulse train including, for each frequency-chirped pulse of the pulse train:
generating a baseband frequency-chirped pulse;
upconverting the baseband frequency-chirped pulse to generate an upconverted frequency-chirped pulse; and
frequency multiplying the upconverted frequency-chirped pulse to produce the at least one frequency-chirped pulse in the pulse train.

28. The method of claim 25 , wherein the pulse train is a first pulse train of a plurality of pulse trains, and wherein the phase-coherent frequency-chirped pulses in the first pulse train of the plurality of pulse trains have the same phase as the phase-coherent frequency-chirped pulses in at least one other pulse train of the plurality of pulse trains.

29. The method of claim 25 , the pulse train having a first comb peak separation, the method further comprising mixing the sample response with a frequency domain comb, the frequency domain comb having a second comb peak separation that is greater than the

Assignees

• Univ Virginia Patent Foundation

Inventors

• Pate Brooks Hart
• Lehmann Kevin K

Classifications

• G01N21/31

  Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)} · CPC title

• G01N21/62

  Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light · CPC title

• G01N22/00

  Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more (G01N3/00 - G01N17/00, G01N24/00 take precedence) · CPC title

• G01N21/69

  specially adapted for fluids {, e.g. molten metal} · CPC title

• G01N21/67

  using electric arcs or discharges · CPC title