Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Modern Optics

Delayed rapid passage and transient gain signals generated using a chirped 8 μm quantum cascade laser

GEOFFREY DUXBURY, Nigel Langford, Kenneth G. Hay

Published Nov 10, 2008• 11 citations
Publisher

Abstract

Rapid passage signals have been observed in which a delayed switch from absorption to emission is observed as the optical density of acetylene in a long path length cell is increased. The delayed switch results in the generation of a large, narrow, transient gain signal. Using numerical solutions of the Maxwell–Bloch equations we have demonstrated that this effect is due to constructive interference between the incident laser field and the field generated by the response of the gaseous medium. This occurs owing to the minimal collisional damping at the low gas pressures within the gas cell, so that the chirp rate of the laser is faster than the collisional reorientation time of the molecules.

DOI
10.1080/09500340802315321

Related papers

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

GEOFFREY DUXBURY, James Floyd Kelly, Thomas A. Blake +1 more

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.

The Journal of Chemical Physics•May 7, 2012•8 citations

Rapid passage signals induced by chirped quantum cascade laser radiation: K state dependent-delay effects in the ν_2 band of NH_3

J. H. Northern, Grant A. D. Ritchie, E. P. Smakman +3 more

In this Letter, a 10 microm quantum cascade laser operating in the intrapulse mode is used observe rapid passage (RP) effects within a 40 cm single-pass gas cell containing low pressures of NH(3). The laser tuning range allows the rotational states J=2 with K=0, 1, and 2 to be probed. We show that the RP structures change as a function of optical density and that the magnitude of the delay in the switch from absorption to emission as a function of increased gas pressure is dependent upon the initial value of K. These measurements are qualitatively well modeled using the Maxwell-Bloch equations.

Optics Letters•Aug 12, 2010•5 citations

Chirped quantum cascade laser induced transient gain in strongly absorbing molecular gases

GEOFFREY DUXBURY, Nigel Langford, Kenneth G. Hay

Using a mW power chirped pulse quantum cascade laser propagating in a 60 m pathlength Herriott cell, delayed rapid passage and transient gain signals have been observed in the 8 μm spectrum of acetylene.

Slow and Fast Light (SL)•Jan 1, 2008•0 citations

Rapid passage signals from a vibrationally excited target molecule: a pump and probe experiment with continuous wave quantum cascade lasers

Richard Walker, Jean-Pierre H. van Helden, James M. R. Kirkbride +4 more

Two 5 µm continuous wave quantum cascade lasers are used to perform a counterpropagating pump and probe experiment on a low pressure sample of nitric oxide. The strong pump field excites a fundamental rovibrational transition and the weaker probe field is tuned to the corresponding rotationally resolved hot band transition. When both light fields are in resonance, rapid passage is observed in the hot band absorption lineshape arising from a minimally damped and velocity-selected sample of molecules in the v=1 state. The measured rapid passage signals are well described by a two-level model based on the optical Bloch equations.

Optics Letters•Dec 9, 2011•7 citations

Dynamics of cooperative emissions in a cascade three-level molecular system driven by an ultrashort laser pulse

Ji‐Cai Liu, Wang Chun-Xin, Faris Gel’mukhanov +1 more

This paper investigates the dynamics of cooperative emissions in a cascade three-level system driven by an ultrashort laser pulse by solving numerically the full-wave Maxwell–Bloch equations. The 4, 4'-bis(dimethylamino) stilbene molecule is used as the model molecule because of its strong two-photon absorption property. The two-colour cooperative emissions are studied as functions of molecular number density and dephasing rate of the dipole coherence. The propagation effects on the evolution of the cooperative radiations are also taken into account. The cooperative radiations are enhanced for large number density of the molecule, while the fast dephasing of the dipole coherence reduces the intensity of the cooperative radiations and delays the emission times or even inhibits the formation of the emissions. The delay time of the radiation decreases with the increase of the molecular number density and the propagation distance.

Chinese Physics B•Nov 1, 2008•4 citations

Delayed optical nutation inside a hollow-core photonic crystal fiber filled with acetylene

Manuel Ocegueda, Serguei I. Stepanov, Jordan Diaz +3 more

The delayed optical nutation effect has been used to evaluate the longitudinal relaxation time (T1) inside an acetylene-filled hollow-core photonic crystal fiber (HC-PCF) at room temperature. In this experiment, sequences of two short optical pulses of 30 ns and 15 ns in width, respectively, with the maximum peak power up to ∼2.5 W, were generated at a laser wavelength of 1530.37 nm, which corresponds to the acetylene ro-vibrational P9 absorption line. The gas pressure inside the 1 m-long HC-PCF varied in the range 0.1–1 Torr. Numerical simulations based on the optical Bloch equations allowed us to evaluate the longitudinal relaxation time as T1∼9ns, proving to be fundamentally limited by the transit-time broadening. Also, the obtained results revealed the influence of slow and fast molecules in the form of a non-exponential decay of the delayed-nutation signals.

Journal of Applied Physics•Jun 22, 2020•3 citations
Rapid passage signals have been observed in which a delayed switch from absorption to emission is observed as the optical density of acetylene in a long path length cell is increased. The delayed switch results in the generation of a large, narrow, transient gain signal. Using numerical solutions of the Maxwell–Bloch equations we have demonstrated that this effect is due to constructive interference between the incident laser field and the field generated by the response of the gaseous medium. This occurs owing to the minimal collisional damping at the low gas pressures within the gas cell, so that the chirp rate of the laser is faster than the collisional reorientation time of the molecules.
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.
In this Letter, a 10 microm quantum cascade laser operating in the intrapulse mode is used observe rapid passage (RP) effects within a 40 cm single-pass gas cell containing low pressures of NH(3). The laser tuning range allows the rotational states J=2 with K=0, 1, and 2 to be probed. We show that the RP structures change as a function of optical density and that the magnitude of the delay in the switch from absorption to emission as a function of increased gas pressure is dependent upon the initial value of K. These measurements are qualitatively well modeled using the Maxwell-Bloch equations.
Two 5 µm continuous wave quantum cascade lasers are used to perform a counterpropagating pump and probe experiment on a low pressure sample of nitric oxide. The strong pump field excites a fundamental rovibrational transition and the weaker probe field is tuned to the corresponding rotationally resolved hot band transition. When both light fields are in resonance, rapid passage is observed in the hot band absorption lineshape arising from a minimally damped and velocity-selected sample of molecules in the v=1 state. The measured rapid passage signals are well described by a two-level model based on the optical Bloch equations.
This paper investigates the dynamics of cooperative emissions in a cascade three-level system driven by an ultrashort laser pulse by solving numerically the full-wave Maxwell–Bloch equations. The 4, 4'-bis(dimethylamino) stilbene molecule is used as the model molecule because of its strong two-photon absorption property. The two-colour cooperative emissions are studied as functions of molecular number density and dephasing rate of the dipole coherence. The propagation effects on the evolution of the cooperative radiations are also taken into account. The cooperative radiations are enhanced for large number density of the molecule, while the fast dephasing of the dipole coherence reduces the intensity of the cooperative radiations and delays the emission times or even inhibits the formation of the emissions. The delay time of the radiation decreases with the increase of the molecular number density and the propagation distance.
The delayed optical nutation effect has been used to evaluate the longitudinal relaxation time (T1) inside an acetylene-filled hollow-core photonic crystal fiber (HC-PCF) at room temperature. In this experiment, sequences of two short optical pulses of 30 ns and 15 ns in width, respectively, with the maximum peak power up to ∼2.5 W, were generated at a laser wavelength of 1530.37 nm, which corresponds to the acetylene ro-vibrational P9 absorption line. The gas pressure inside the 1 m-long HC-PCF varied in the range 0.1–1 Torr. Numerical simulations based on the optical Bloch equations allowed us to evaluate the longitudinal relaxation time as T1∼9ns, proving to be fundamentally limited by the transit-time broadening. Also, the obtained results revealed the influence of slow and fast molecules in the form of a non-exponential decay of the delayed-nutation signals.