Delayed pulse dynamics in single mode class B lasers

Ségard, Bernard; Glorieux, P.; Erneux, Thomas

doi:10.1007/s00340-005-2031-y

Cited by 8 publications

(16 citation statements)

References 20 publications

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“…Representative profiles of the (overall) gain G(Ω) and phase-shift Φ(Ω) are shown Fig.4 and Fig.5 for αℓ = 10, with various intensities I in chosen according to criteria analogue to those used Fig.2 and Fig.3. The optical thickness retained is of the order of that actually used in [2]. When…”

Section: System Of Two-level Atomsmentioning

confidence: 99%

“…Ideally bell-shaped pulses can then propagate moderately distorted in such a way that the maximum of the transmitted pulse occurs before that of the incident pulse. Time-advances exceeding 0.5 times the halfduration at half-maximum of the pulse-envelope have been so evidenced in experiments involving a true shape detection of the latter [2]. See also [3,4].…”

Section: Introductionmentioning

confidence: 98%

“…Convincing demonstrations of fast light in a linear homogeneous medium were performed in the 1980s by exploiting the steep anomalous dispersion associated with a well-isolated, narrow and strong absorption line of the medium, leading to negative values of the group velocity [1,2]. Ideally bell-shaped pulses can then propagate moderately distorted in such a way that the maximum of the transmitted pulse occurs before that of the incident pulse.…”

Section: Introductionmentioning

confidence: 99%

“…The dip in the transmission may be natural or created in various arrangements involving electromagnetically induced absorption [6,7], stimulated Raman [8] or Brillouin [9] scattering, etc. The literature on fast light is abundant (for reviews, see, e.g., [10][11][12][13]) but it seems that the fractional pulse-advance with moderate distortion reported in [2] has not been overtaken. This is easily explained by remarking that, since the transmission dip at the carrier frequency must be well pronounced, there are spectral regions where the overall transmission of the system is much larger.…”

Section: Introductionmentioning

confidence: 99%

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From fast to slow light in a resonantly driven absorbing medium

Macke

Ségard

2010

Phys. Rev. A

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We theoretically study the propagation through a resonant absorbing medium of a time-dependent perturbation modulating the amplitude of a continuous wave (cw). Modeling the medium as a twolevel system and linearizing the Maxwell-Bloch equations for the perturbation, we establish an exact analytical expression of the transfer function relating the Fourier transforms of the incident and transmitted perturbations. It directly gives the gain and the phase shift undergone in the medium by a harmonic modulation. For the case of a pulse modulation, it enables us to determine the transmission time of the pulse center-of-mass (group delay), evidencing the relative contributions of the coherent and incoherent (population) relaxation. We show that the group delay has a negative value (fast light) fixed by the coherent effects when the cw intensity is small compared to the saturation intensity and becomes positive (slow light) when this intensity increases, before attaining a maximum that cannot exceed the population relaxation time. The analytical results are completed by numerical determinations of the shape of the transmitted pulses in the different regimes.

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Section: System Of Two-level Atomsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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From fast to slow light in a resonantly driven absorbing medium

Macke

Ségard

2010

Phys. Rev. A

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“…The major challenge in such experiments is to obtain advancements comparable to the pulse duration with moderate distortion. Convincing experiments have been performed in the 1980s [2,3] in media with a narrow absorption line. Unfortunately, superluminal propagation is then accompanied by strong absorption.…”

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confidence: 99%

Comment on: Gain-assisted superluminal light propagation through a Bose-Einstein condensate cavity system

Macke

Ségard

2016

Eur. Phys. J. D

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Abstract. In a recent theoretical article [S.H. Kazemi, S. Ghanbari, M. Mahmoudi, Eur. Phys. J. D 70, 1 (2016)], Kazemi et al. claim to have demonstrated superluminal light transmission in an optomechanical system where a Bose-Einstein condensate serves as the mechanical oscillator. In fact the superluminal propagation is only inferred from the existence of a minimum of transmission of the system at the probe frequency. This condition is not sufficient and we show that, in all the cases where superluminal propagation is claimed by Kazemi et al., the propagation is in reality subluminal. Moreover, we point out that the system under consideration is not minimum-phase-shift. The Kramers-Kronig relations then only fix a lower limit to the group delay and we show that these two quantities have sometimes opposite signs.When the transmission of light in a given medium displays a well-marked narrow dip at some frequency, the group velocity at this frequency may be larger than the velocity of light in vacuum or even negative. An ideally smooth light-pulse can then exits the medium without significant distortion before than if it had propagated in vacuum [1]. Such superluminal or fast propagation is not at odds with relativistic causality since a given point of the output-pulse profile is not a direct reflection of the homologous point of the incident-pulse profile but results from the action of the medium on all the earlier part of the incident pulse. The major challenge in such experiments is to obtain advancements comparable to the pulse duration with moderate distortion. Convincing experiments have been performed in the 1980s [2,3] in media with a narrow absorption line. Unfortunately, superluminal propagation is then accompanied by strong absorption. This inconvenience is overcome by using a medium with a doublet of gain lines [4,5] and a minimum of transmission between them. Significant advancements have been evidenced in an atomic vapor with this arrangement [6]. A comprehensive review on fast light in atomic media can be found in [7]. Experiments involving four wave mixing are reported in [8].Superluminal or subluminal propagation can only be demonstrated by a determination of the group delay and one should not hastily conclude from what it precedes that every gain system with a dip in its transmission curve will be superluminal. This extrapolation is unfortunately made in a recent theoretical article [9] whose authors claim to have evidenced superluminal propagation by giving this a e-mail :bernard.segard@univ-lille1.fr sole argument. The system under consideration is an optomechanical device consisting in a high-quality optical cavity containing a Bose-Einstein condensate (BEC) of Rubidium atoms which serves as the mechanical oscillator [10]. It is submitted to a strong pump field (continuous wave) and to a weak probe field. In a frame rotating at the pump angular-frequency, the transfer function for the probe field reads as [9] 1withIn these expressions, κ (γ m ) is the damping rate of the cavity (the mechanic...

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