Related papers: Pulsed light beams in vacuum with superluminal and…
The group velocity for pulses in an optical medium can be negative at frequencies between those of a pair of laser-pumped spectral lines. The gain medium then can amplify the leading edge of a pulse resulting in a time advance of the pulse…
The mechanisms leading to a seemingly superluminal propagation of light in dispersive media are examined. The anomalous dispersion near an absorption line, involved in the first experiments displaying negative group velocity propagation, is…
Anomalous dispersion cannot occur in a transparent passive medium where electromagnetic radiation is being absorbed at all frequencies, as pointed out by Landau and Lifshitz. Here we show, both theoretically and experimentally, that…
We consider pulse propagation in a linear anomalously dispersive medium where the group velocity exceeds the speed of light in vacuum (c) or even becomes negative. A signal velocity is defined operationally based on the optical…
We present a simple electronic circuit which produces negative group delays for base-band pulses. When a band-limited pulse is applied as the input, a forwarded pulse appears at the output. The negative group delays in lumped systems share…
We report on the four-wave mixing of superluminal pulses, in which both the injected and generated pulses involved in the process propagate with negative group velocities. Generated pulses with negative group velocities of up to…
We investigate the propagation of a pulse field in an optomechanical system. We examine the question of advance of the pulse under the conditions of electromagnetically induced transparency in the mechanical system contained in a high…
In this Chapter the time-domain analysis of the velocity of the electromagnetic field pulses generated by a spatially compact source in free space is presented. Recent simulations and measurements of anomalous superluminal, subluminal, and…
The propagation of light-pulse with negative group-velocity in a nonlinear medium is studied theoretically. We show that the necessary conditions for these effects to be observable are realized in a three-level $\Lambda$-system interacting…
A plane monochromatic wave propagates in vacuum at the velocity of c. However, wave packets limited in space and time are used to transmit energy and information. Here it has been shown based on the wave approach that the on-axis part of…
We experimentally study the group time delay for a light pulse propagating through hot Rb vapor in the presence of a strong coupling field in a $\Lambda$ configuration. We demonstrate that the ultra-slow pulse propagation is transformed…
Einstein's theory of relativity establishes the speed of light in vacuum, c, as a fundamental constant. However, the speed of light pulses can be altered significantly in dispersive materials. While significant control can be exerted over…
Precise knowledge of the behaviour of the phase of light in a focused beam is fundamental to understanding and controlling laser-driven processes. More than a hundred years ago an axial phase anomaly for focused monochromatic light beams…
Slow light in moving media reaches a paradoxical regime when the flow speed of the medium approaches the group velocity of light. Pulses can penetrate a region where a counter-propagating flow exceeds the group velocity. When the…
Group delay for a reflected light pulse from a weakly absorbing dielectric slab is theoretically investigated, and large negative group delay is found for weak absorption near a resonance of the slab ($Re(kd)=m\pi$). The group delays for…
Recently, a series of theoretical and experimental papers on free-space propagation of pulsed Laguerre-Gaussian and Bessel beams was published, which reached contradictory and controversial results about group velocities of such pulses.…
We examine the propagation of a weak probe light through a coherently driven $Y$-type system. Under the condition that the excited atomic levels decay via same vacuum modes, the effects of quantum interference in decay channels are…
We analytically study the linear propagation of arbitrarily shaped light-pulses through an absorbing medium with a narrow transparency-window or through a resonant amplifying medium. We point out that, under certain general conditions, the…
We present a simple electronic circuit which provides negative group delays for band-limited, base-band pulses. It is shown that large time advancement comparable to the pulse width can be achieved with appropriate cascading of…
We consider pulse propagation through a two component composite medium (metal inclusions in a dielectric host) with or without cavity mirrors. We show that a very thin slab of such a medium, under conditions of localized plasmon resonance,…