Observation of infrared free-induction decay and optical nutation signals from nitrous oxide using a current modulated quantum cascade laser

Geoffrey Duxbury, James F. Kelly, Thomas A. Blake, Nigel Langford

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Free induction decay (FID), optical nutation, and rapid passage induced signals in nitrous oxide, under both optically thin and optically thick conditions, have been observed using a rapid current pulse modulation, or chirp, applied to the slow current ramp of a quantum cascade (QC) laser. The variation in optical depth was achieved by increasing the pressure of nitrous oxide in a long path length multipass absorption cell. This allows the variation of optical depth to be achieved over a range of low gas pressures. Since, even at the highest gas pressure used in the cell, the chirp rate of the QC laser is faster than the collisional reorientation time of the molecules, there is minimal collisional damping, allowing a large macroscopic polarization of the molecular dipoles to develop. This is referred to as rapid passage induced polarization. The resultant FID signals are enhanced due to the constructive interference between the field within the gas generated by the slow ramp of the laser (pump), and that of the fast chirp of the laser (probe) signal generated by pulse modulation of the continuously operating QC laser. The FID signals obtained at large optical depth have not been observed previously in the mid-infrared regions, and unusual oscillatory signals have been observed at the highest gas pressures used. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4710540]

LanguageEnglish
Article number174317
Number of pages14
JournalJournal of Chemical Physics
Volume136
Issue number17
DOIs
Publication statusPublished - 7 May 2012

Fingerprint

Quantum cascade lasers
nutation
nitrous oxides
Nitrous Oxide
quantum cascade lasers
induction
Gases
Pulse modulation
Infrared radiation
chirp
optical thickness
pulse modulation
gas pressure
decay
ramps
Polarization
Lasers
polarization
cells
Damping

Keywords

  • infrared spectra
  • nitrogen compounds
  • optical coherent transients
  • optical modulation
  • quantum cascade laser

Cite this

@article{a4679e5df60e43e3b6f6a096da055fe3,
title = "Observation of infrared free-induction decay and optical nutation signals from nitrous oxide using a current modulated quantum cascade laser",
abstract = "Free induction decay (FID), optical nutation, and rapid passage induced signals in nitrous oxide, under both optically thin and optically thick conditions, have been observed using a rapid current pulse modulation, or chirp, applied to the slow current ramp of a quantum cascade (QC) laser. The variation in optical depth was achieved by increasing the pressure of nitrous oxide in a long path length multipass absorption cell. This allows the variation of optical depth to be achieved over a range of low gas pressures. Since, even at the highest gas pressure used in the cell, the chirp rate of the QC laser is faster than the collisional reorientation time of the molecules, there is minimal collisional damping, allowing a large macroscopic polarization of the molecular dipoles to develop. This is referred to as rapid passage induced polarization. The resultant FID signals are enhanced due to the constructive interference between the field within the gas generated by the slow ramp of the laser (pump), and that of the fast chirp of the laser (probe) signal generated by pulse modulation of the continuously operating QC laser. The FID signals obtained at large optical depth have not been observed previously in the mid-infrared regions, and unusual oscillatory signals have been observed at the highest gas pressures used. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4710540]",
keywords = "infrared spectra, nitrogen compounds, optical coherent transients, optical modulation, quantum cascade laser",
author = "Geoffrey Duxbury and Kelly, {James F.} and Blake, {Thomas A.} and Nigel Langford",
year = "2012",
month = "5",
day = "7",
doi = "10.1063/1.4710540",
language = "English",
volume = "136",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
number = "17",

}

Observation of infrared free-induction decay and optical nutation signals from nitrous oxide using a current modulated quantum cascade laser. / Duxbury, Geoffrey; Kelly, James F.; Blake, Thomas A.; Langford, Nigel.

In: Journal of Chemical Physics , Vol. 136, No. 17, 174317, 07.05.2012.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Observation of infrared free-induction decay and optical nutation signals from nitrous oxide using a current modulated quantum cascade laser

AU - Duxbury, Geoffrey

AU - Kelly, James F.

AU - Blake, Thomas A.

AU - Langford, Nigel

PY - 2012/5/7

Y1 - 2012/5/7

N2 - Free induction decay (FID), optical nutation, and rapid passage induced signals in nitrous oxide, under both optically thin and optically thick conditions, have been observed using a rapid current pulse modulation, or chirp, applied to the slow current ramp of a quantum cascade (QC) laser. The variation in optical depth was achieved by increasing the pressure of nitrous oxide in a long path length multipass absorption cell. This allows the variation of optical depth to be achieved over a range of low gas pressures. Since, even at the highest gas pressure used in the cell, the chirp rate of the QC laser is faster than the collisional reorientation time of the molecules, there is minimal collisional damping, allowing a large macroscopic polarization of the molecular dipoles to develop. This is referred to as rapid passage induced polarization. The resultant FID signals are enhanced due to the constructive interference between the field within the gas generated by the slow ramp of the laser (pump), and that of the fast chirp of the laser (probe) signal generated by pulse modulation of the continuously operating QC laser. The FID signals obtained at large optical depth have not been observed previously in the mid-infrared regions, and unusual oscillatory signals have been observed at the highest gas pressures used. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4710540]

AB - Free induction decay (FID), optical nutation, and rapid passage induced signals in nitrous oxide, under both optically thin and optically thick conditions, have been observed using a rapid current pulse modulation, or chirp, applied to the slow current ramp of a quantum cascade (QC) laser. The variation in optical depth was achieved by increasing the pressure of nitrous oxide in a long path length multipass absorption cell. This allows the variation of optical depth to be achieved over a range of low gas pressures. Since, even at the highest gas pressure used in the cell, the chirp rate of the QC laser is faster than the collisional reorientation time of the molecules, there is minimal collisional damping, allowing a large macroscopic polarization of the molecular dipoles to develop. This is referred to as rapid passage induced polarization. The resultant FID signals are enhanced due to the constructive interference between the field within the gas generated by the slow ramp of the laser (pump), and that of the fast chirp of the laser (probe) signal generated by pulse modulation of the continuously operating QC laser. The FID signals obtained at large optical depth have not been observed previously in the mid-infrared regions, and unusual oscillatory signals have been observed at the highest gas pressures used. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4710540]

KW - infrared spectra

KW - nitrogen compounds

KW - optical coherent transients

KW - optical modulation

KW - quantum cascade laser

UR - http://www.scopus.com/inward/record.url?scp=84862858577&partnerID=8YFLogxK

U2 - 10.1063/1.4710540

DO - 10.1063/1.4710540

M3 - Article

VL - 136

JO - Journal of Chemical Physics

T2 - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 17

M1 - 174317

ER -