Chirped pulse frequency-domain comb for spectroscopy

1. A method, comprising:

generating a pulse train comprising chirped pulses of electromagnetic energy, the respective chirped pulses including a frequency sweep across a first specified bandwidth during a respective chirped pulse duration, the respective chirped pulse duration establishing a first frequency-domain comb peak separation; and

exciting a sample using the pulse train;

wherein a width of a frequency-domain comb peak is established at least in part by a total duration of the pulse train; and

wherein a bandwidth of a first frequency-domain comb is determined at least in part by the first specified bandwidth of the frequency sweep of the respective chirped pulses.

2. The method of claim 1 , wherein the pulse train comprises chirped pulses respectively sweeping across a first range of frequencies corresponding to the first specified bandwidth, and wherein the method comprises:

upconverting the pulse train to a higher second range of frequencies;

frequency multiplying the pulse train to establish a wider second specified bandwidth of the first frequency-domain comb; and

wherein the exciting a sample using the pulse train comprises exciting the sample using the upconverted and frequency multiplied pulse train.

3. The method of claim 1 , wherein generating the pulse train includes applying a specified time-domain window to shape one or more of the pulse train or respective chirped pulses.

4. The method of claim 1 , wherein the generating the pulse train includes using an arbitrary waveform generator (AWG).

5. The method of claim 1 , comprising:

obtaining a time-domain response from the sample in response to the excitation of the sample; and

mixing the time-domain response with a second time-domain signal corresponding to a second frequency-domain comb, the second frequency-domain comb including a comb peak separation that is larger than the first frequency-domain comb peak separation.

6. The method of claim 5 , wherein the mixing the time-domain response with a second time-domain signal includes generating a bandwidth-compressed response including interleaved frequency-domain information corresponding to the time-domain response of the sample.

7. The method of claim 5 , comprising transforming the time-domain response to obtain one or more of frequency-domain magnitude or phase information corresponding to the second, higher range of frequencies and the wider second specified bandwidth of the first frequency-domain comb.

8. The method of claim 7 , comprising determining a characteristic of the sample using the magnitude or phase information.

9. The method of claim 1 , comprising generating a specified time-domain phase offset to successive chirped pulses included in the pulse train to establish a specified frequency shift of the frequency-domain comb.

10. The method of claim 9 , comprising generating the specified time-domain phase offset to establish the second frequency-domain comb, the second frequency-domain comb including comb peaks located between the locations of the frequency-domain comb peaks of the first frequency-domain comb.

11. An apparatus, comprising:

a waveform generator circuit configured to generate a pulse train comprising chirped pulses of electromagnetic energy to excite a sample, the respective chirped pulses including a frequency sweep across a first specified bandwidth during a respective chirped pulse duration, the respective chirped pulse duration establishing a first frequency-domain comb peak separation;

wherein a width of a frequency-domain comb peak is established at least in part by a total duration of the pulse train; and

wherein a bandwidth of a first frequency-domain comb is determined at least in part by the first specified bandwidth of the respective chirped pulses.

12. The apparatus of claim 11 , wherein the pulse train comprises chirped pulses respectively sweeping across a first range of frequencies corresponding to the first specified bandwidth, and wherein the apparatus comprises:

a first mixer circuit configured to upconvert the pulse train to a higher second range of frequencies; and

a frequency multiplier configured to multiply the frequency of the pulse train to establish a wider second specified bandwidth of the first frequency-domain comb in the higher second range of frequencies to excite the sample.

13. The apparatus of claim 11 , wherein the pulse train includes a specified time-domain window to shape one or more of the pulse train or respective chirped pulses.

14. The apparatus of claim 11 , comprising a detector configured to obtain a time-domain response from the sample in response to the excitation of the sample.

15. The apparatus of claim 11 , comprising:

a detector configured to obtain a time-domain response from the sample in response to the excitation of the sample; and

a second mixer circuit configured to mix the time-domain response with a second time-domain signal corresponding to a second frequency-domain comb, the second frequency-domain comb including a comb peak separation that is larger than the first frequency-domain comb peak separation.

16. The apparatus of claim 15 , wherein the second mixer circuit is configured to generate a bandwidth-compressed response including interleaved frequency-domain information corresponding to the time-domain response of the sample.

17. The apparatus of claim 15 , comprising a signal processor circuit configured to transform the time-domain response to obtain one or more of frequency-domain magnitude or phase information corresponding to the second, higher range of frequencies and the wider second specified bandwidth of the first frequency-domain comb.

18. The apparatus of claim 17 , wherein the signal processor circuit is configured to determine a characteristic of a sample using the magnitude or phase information.

19. The apparatus of claim 11 , wherein the waveform generator circuit is configured to generate a specified time-domain phase offset to successive chirped pulses included in the pulse train to establish a specified frequency shift of the frequency-domain comb.

20. The apparatus of claim 19 , wherein the waveform generator is configured to generate the specified time-domain phase offset to establish the second frequency-domain comb, the second frequency-domain comb including comb peaks located between the locations of the frequency-domain comb peaks of the first frequency-domain comb.

21. An apparatus, comprising:

means for generating a pulse train comprising chirped pulses of electromagnetic energy to excite a sample, the respective chirped pulses including a frequency sweep across a first specified bandwidth during a respective chirped pulse duration, the respective chirped pulse duration establishing a first frequency-domain comb peak separation; and

wherein a width of a frequency-domain comb peak is established at least in part by a total duration of the pulse train; and

wherein a bandwidth of a first frequency-domain comb is determined at least in part by the first specified bandwidth of the frequency sweep of the respective chirped pulses.

22. The apparatus of claim 21 , wherein the pulse train comprises chirped pulses respectively sweeping across a first range of frequencies corresponding to the first specified bandwidth, and wherein the apparatus comprises:

means for upconverting the pulse train to a higher second range of frequencies; and

means to multiply the frequency of the pulse train to establish a wider second specified bandwidth of the first frequency-domain comb in the higher second range of frequencies to excite the sample.

23. The apparatus of claim 21 , comprising:

means for obtaining a time-domain response of the sample;

means for providing a bandwidth-compressed response including interleaved frequency-domain information corresponding to the time-domain response of the sample.