Feed-forward spectral calibration methodology for line-scanned tunable laser absorption spectroscopy
A generalized feed-forward method for accurate tunable laser absorption spectroscopy includes generating a laser beam. The generated laser beam is directed down a reference path and a test/sample path. One or more parameters are extracted from the reference path. The one or more parameters, extracted from the reference path, are used as feed-forward, to adjust spectral analysis of the test/sample path to detect a composition and/or concentration of an analyte gas within the test/sample path. The extraction of the one or more parameters from the reference path and the spectral analysis of the test/sample path are performed substantially concurrently.
1. A generalized feed-forward method for accurate tunable laser absorption spectroscopy, comprising:
generating a laser beam,
directing, the generated laser beam down a reference path and a test/sample path:
extracting two spectral line shape parameters ζ W and ζ C from the reference path; and
using the two spectral line shape parameters ζ W and ζ C extracted from the reference path, as feed-forward, and one analyte concentration parameter C A concurrently extracted from the test/sample path to iterate a Voigt-based fitting model and direct a composition and/or concentration of an analyte gas within the test/sample path, using the Voigt-based fitting model that has been integrated using ζ w , ζ c and C A as key least-mean squares LMS fitting parameters,
wherein the extraction of the two spectral line shape parameters ζ W and ζ C , from the reference path and the extraction of the analyte concentration parameter C A from the test/sample path are performed concurrently.
2. The method of claim 1 , wherein the two spectral fine shape parameters ζ W and ζ C include line-width and line-center.
3. The method of claim 1 , wherein the extraction of the two spectral line shape parameters ζ W and ζ C from the test sample path and the extraction of the analyte concentration parameter C A from the test/sample path are performed a plurality of times to repeatedly iterate the Voigt-based fitting model.
4. The method of claim 1 , wherein iterating the Voight-based fitting model includes correcting for laser ramp bias and/or correcting for range fluctuations.
5. The method of claim 1 , wherein the method is performed in a free-space optical system, a fiber-based sensing system, and/or an on-chip photonic chip sensor.
6. The method of claim 1 , wherein the generated laser beam is ramped using a laser ramping signal that has a soft transition at a start of each pulse and an offset between periods.
7. The method of claim 6 , wherein the laser ramping signal is a sawtooth wave with soft transitions and the offset between periods.
8. A computer program product for generalized feed-forward method for accurate tunable laser absorption spectroscopy, the computer program product comprising a tangible computer readable storage medium having program instructions embodied therewith, the program instructions executable by a computer to cause the computer to:
generating a laser beam;
directing the generated laser beam down a reference path and a test/sample path:
extracting two spectral line shape parameters ζ W and ζ C from the reference path: and
using the two spectral line shape parameters ζ W and ζ C , extracted from the reference path, as feed-forward, and one analyte concentration parameter C A concurrently extracted from the test/sample path to iterate a Voigt-based fitting model and detect a composition and/or concentration of an analyte gas within the test/sample path, using the Voigt-based fitting model that has been integrated using ζ W , ζ C , and C A as key least-mean squares LMS fitting parameters,
wherein the extraction of the two spectral line shape parameters ζ W and ζ C from the reference path and the extraction of the analyte concentration parameter C A from the test/sample path are performed concurrently.
9. The computer program product of claim 8 , wherein the two spectral line shape parameters ζ W and ζ C include line-width and line-center.
10. The computer program product of claim 8 , wherein iterating the Voigt-based fitting model includes correcting for laser ramp bias and/or correcting for range fluctuations.
11. The computer program product of claim 8 , wherein the method is performed in a free-space optical system, a fiber-based sensing system, and/or aft on-chip photonic chip sensor.
12. The computer program product of claim 8 , wherein the generated laser beam is ramped using a laser ramping signal that has a soft transition at a start of each pulse and an offset between periods.
13. The computer program product of claim 12 , wherein the laser ramping signal is a sawtooth wave with soft transitions and the offset between periods.
14. The computer program product of claim 8 , wherein the extraction of the two spectral line shape parameters ζ W and ζ C from the test/sample path and the extraction of the analyte concentration parameter C A from the test/sample path are performed a plurality of times to repeatedly iterate the Voigt-based fitting model.