june 21st 2011 66 osu mol. spect. symp.tb03 8:59 a.m sub-doppler spectra of infrared hyperfine...

June 21st 2011 66 OSU Mol. Spect. Symp.TB03 8:59 a.m

Sub-Doppler Spectra of Infrared Hyperfine Transitions of Nitric Oxide using

a Pulse Modulated Quantum Cascade Laser

Geoffrey Duxbury, and Nigel LangfordDepartment of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow, G4 0NG, UK [email protected]

James F. Kelly and Thomas A. BlakeEnvironmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, PO Box 999, MS K-88. Richland, Washington 99352


Outline of Talk• Schematic diagrams of NO IR transitions• Location of origins of chirped pulses• Sub-doppler signals in the R11.5 transition• Field effects on hyperfine splitting• Zoomed view of sub-Doppler signals• Field effects on R18.5 resolved doublet• Autler Townes splitting• 15NO• Conclusion


Schematic diagrams of the Doppler broadened envelopes and hyperfine structures of the 14NO transitions studied in these experiments

(a)

(b)


Slow experimental scans showing the locations of the perturbation pulses for (i)

and (ii).

(i) (ii)

June 21 st 2011 66 OSU Mol. Spect. Symp.TB03 8:59 a.m

(R), Rapid voltage pulse induced experimental QC laser scans through the R 11.5 unresolved doublet from red (a) and (b) blue detuned.

(C) Calculated real part of the refractive index for (a) red and (b) blue detuned.

(R) (C)

June 21nd 2011 66 OSU Mol. Spect. Symp.TB03 8:59 a.m

Expanded difference plots of the observed field dependent hyperfine structure of the R 11.5 unresolved doublet. (i) Herriott cell, (ii) short cell.

(a) red detuned, blue chirp, (b) blue detuned,red chirp. In (c) the scale in (b) has been expanded to show free induction decay (FID) like behaviour on the e-e lambda doublet.

The field induced splittings of the f-f lambda doublet are more marked in the rebound phase.


Rapid experimental scans through the resolved doublet, start red detuned by at least one Doppler width. Initial scan direction is blue (to higher frequency).

(C)

(i) 10 cm ref cell.

simple doublet

(ii) 100 m Herriott cell (HC), complex pattern.

(a) Full scan.

(b) HC, 6 line pattern

(c) HC, 6 line pattern & power reduced by rotating a linear polarizer

(d) Ref cell & power reduced by rotating a linear polarizer


Rapid experimental scans through the resolved doublet, start red detuned by at least one Doppler width. Initial scan direction is red (to lower frequency). (i) ref cell. (ii) 100 m cell.

full red scan, no spectra are observed in the direct scan, doublet structure seen via nutation generated by the large laser induced field in the rebound phase.

The pattern in (ii), 100m cell is complex, but with poorer resolution than that shown in previous figure

The region around the nutation generated doublet. In (ii), 100 m path length a large Autler-Townes splitting is seen

,


Rapid experimental scans through the R 18.5 resolved doublet, starting blue detuned by at least one Doppler width. The initial scan direction is red, to lower frequency.(i) the 10 cm ref cell. (ii) the 100 m Herriott cell

a) full scan showing the resolved doublet in spectrum (i), whereas in the Herriott cell spectrum (ii) a more complex pattern may be seen

b) the region round the doublet is expanded

c) spectra are shown as the power is reduced using a linear polariser. At low power the doublet structure is almost recovered


Rapid scan through the R 18.5 resolved doublet. Probe pulse starts between the two components. Initial direction of fast scan is to lower frequency (a red chirp). In the rebound it scans through both components hence observation of a doublet, but nutation region signal has only one component.

(a) full scan, power dependence of Autler Townes splitting of single component.

(b) the scan is expanded to show the region of the direct scan and rebound.

(c) the power dependence of the complex doublet structure is shown, collapsing to the simple doublet structure of the spectrum obtained using the short cell.

June 21nd 2011 66 OSU Mol. Spect. Symp.TBB03 8:59 a.m

Scans through the R 24.5 transition of the band of 15NO, a resolved doublet, starting red detuned by at least one Doppler width. The initial scan direction is blue (to higher frequency). (i) the initial perturbation pulse direction is a

red chirp(ii) the initial pulse direction corresponds to a

blue chirp

a) Full range, note the Autler-Townes splitting in each component of the doublet.

b) An expanded view of the origin showing that the power broadened doublet is seen using the blue chirp only.

Since the nuclear spin of 15N is 0.5, the number of hyperfine components is reduced, and little structure may be seen in either the direct or rebound signals.

As with 14NO the large nutation signals are anti-correlated with the observation of the power broadened doublet in the direct scan.


Polarizer settings for power reduction

Polariser reading, degrees

Effective polarization angle0

Effective transmission

59 90 0.069 80 0.03079 70 0.11789 60 0.25099 50 0.413109 40 0.587119 30 0.750129 20 0.883139 10 0.970149 0 1.0

June 21nd 2011 65 OSU Mol. Spect. Symp.TE08 10:47 a.m

Conclusions•QC lasers can cause the build up of a large macroscopic polarization in a molecular gas

•In an open shell molecule the large polarization may lead to the generation of field induced non-linear absorption

•Non-linearity is enhanced by rapid passage effects caused by rapidly chirped perturbation pulses

•Large AC Stark effects may be generated leading to sub-Dopper resolution and large splittings greater than the Doppler width of absorption lines.


Acknowledgements This research was performed at the W.R. Wiley Environmental Molecular Sciences Laboratory, a national user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at the Pacific Northwest National Laboratory. Pacific Northwest National Laboratory is operated for the United States Department of Energy by Battelle under Contract DE-AC06-76RLO 1830.

G. Duxbury would like to thank The Leverhulme trust for the award of an Emeritus Fellowship, and the Royal Society of Edinburgh for the award of a travel grant.


References[ReferencesS.H. Autler and C.H. Townes, Phys. Rev. 100, 703-722 (1955)G. Duxbury, N. Langford, M.T. McCulloch and S. Wright, Mol. Phys. 105, 741-754 (2007)G. Duxbury, J.F. Kelly, T.A. Blake and N. Langford, in “Coherence and Quantum Optics IX, Ed. N.P. Bigelow, J.H. Eberley and C.R. Stroud, Jr, ODA, 468-469 (2008)J.T. Remillard, D. Uy, W.H. Weber, W.H. Weber, F. Capasso, C. Gmachl, A.L. Hutchinson, D.L. Sivco, J.N. Baillargeon and A.Y. Cho, Opt. Express, 7, 243-248 (2000)A.Z. Genack, R.M. Macfarlane and R.G. Brewer, Phys. Rev. Lett, 237, 1078-1080 (1976)A.Z. Genack and R.G. Brewer, Phys. Rev. Lett, 40, 862-865 (1978)R.G. DeVoe and R,G, Brewer, Phys. Rev. Lett., 40, 862-865 (1978)R.M. Macfarlane and M. Zhu, “Observation of optical coherent transients by current switching a semiconductor diode laser”, in Quantum Electronics and Laser Science Conference, Vol 16 of 1995 OSA Technical Digest series (Optical Society of America, Washington D.C., 1995) p.248Y.-Q. Li,W.H. Burkett and M. Xiao, Opt. Lett. 21, 982-984 (1996)R.M. Macfarlane and M. Zhu,, Opt. Lett., 22, 248-250 (1997)P.Dubé, M.D. Levenson and J.L. Hall, Opt. Lett, 22, 184-186 (1997)R.G. Brewer and R.L. Shoemaker, Phys. Rev. A6, 2001-7 (1972)S.W. Sharpe, J.F. Kelly, J.S. Hartman, C. Gmachl, F. Capasso, D.L. Sivco, J.N. Baillargeon and A.Y. Cho, Optics Lett., 23, 1396 (1998)J.F. Kelly, R.S. Disselkamp, R.L. Sams, T.A. Blake, S.W. Sharpe, D.A. Richter and A. Fried, Proc. SPIE 4817, 43-72 (2002)A.G. Maki and J.S. Wells, “Wavenumber Calibration Tables for Laser Heterodyne Measurements, NIST Special. Pub. 821 (1991)B. Macke, P. Glorieux, A. Jacques and J. Legrand, J. Phys. B. At. Mol. Phys., 14, 447-457 (1981)

june 21st 2011 66 osu mol. spect. symp.tb03 8:59 a.m sub-doppler spectra of infrared hyperfine...

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