Controlling the Velocity of Light Pulses

Optics Communications, 2016

We show how the velocity of an optical pulse propagating through a dispersive medium depends on the pulse duration. A transition from the group velocity for long pulses to the in-vacuum velocity for short pulses is shown both in experimental results and in theoretical predictions. The temporal duration of the experimental pulses are 150 ps and 3.5 ns. A description of the pulse propagation in terms of the time "center of mass" of the energy flow allows an intuitive overview of the results.

IEEE Journal of Selected Topics in Quantum Electronics, 2000

Physical Review A, 2006

We report experimental evidence that light storage, understood as the controlled release of a light pulse by an atomic sample dependent on the past presence of a writing pulse, is not restricted to small-group-velocity media but can also occur in a negative-group-velocity ...

… Electronics and Laser …, 2005

We show that there are no fundamental limits to the maximum time delay that can be achieved for pulses propagating through slow-light media, thus suggesting the importance of slow-light methods for practical applications.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2003

We report experimental results on slowing a light pulse in a system for amplification without inversion (AWI). We were able to control a subluminal group velocity continuously from V g = c/2850 to c/7260 by just changing an incoherent pumping beam power from 0 to 12 mW in the AWI system. And several advantages, such as the controllable delay time and the pulse amplification, for slowing of the light in the AWI system compared to in an electromagnetically induced transparency system were found.

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2011

In the framework of the nonlinear Λ model, propagation of solitons was analysed in atomic vapours and Bose–Einstein condensates. The complicated nonlinear interplay between fast and slow-light solitons in a Λ -type medium was shown to facilitate control of its optical transparency and formation of optical gates. An exact analytical description was given for the deceleration, stopping and revival of slow-light solitons in the experimentally relevant non-adiabatic regime. A stopping slow-light soliton imprints a localized immobile polarization pattern in the medium, which, as explicitly demonstrated here, can be used as a bit of readable optical memory. The whole process can be controlled with the background field and an auxiliary laser field. The latter regulates the signal velocity, while the slow-light soliton can be stopped by switching off the former. The location and shape of the imprinted memory bit were also determined. With few assumptions characteristic of slow light, the Λ ...

The European Physical Journal D - Atomic, Molecular and Optical Physics, 2003

This paper deals with the apparent superluminal propagation of electromagnetic pulses in a linear dispersive medium. One specifically examines the possibility that the pulse leaving the medium may be nearly identical to the incident one (low distortion) and in significant advance of it (strongly negative groupdelays). Favourable conditions are obtained in a dilute medium where the required anomalous dispersion originates in an ensemble of narrow absorption or gain lines. Analytical expressions of the advancement of the pulse centre-of-gravity and of the lowest order distortion are established from the transfer-function of the medium. The experiments already achieved with arrangements involving a single absorption-line or a gain-doublet are analysed in detail and compared. The considerable difficulties to overcome in order to attain advancements comparable to the pulse width without important distortion are pointed out. New and promising schemes involving a narrow dip in a gain profile or absorption-doublets are proposed. PACS. 42.25.Bs Wave propagation, transmission and absorption-42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light-03.65.Sq Semiclassical theories and applications 126 The European Physical Journal D results of our work and stressing the severe constraints to the observation of significant pulse advancements.

2004

We investigate propagation of a slow-light soliton in atomic vapors and Bose-Einstein condensates described by the nonlinear Lambda-model. We show that the group velocity of the soliton monotonically decreases with the intensity of the controlling laser field, which decays exponentially after the laser is switched off. The shock wave of the vanishing controlling field overtakes the slow soliton and stops it, while the optical information is recorded in the medium in the form of spatially localized polarization. We find an explicit exact solution describing the whole process within the slowly varying amplitude and phase approximation. Our results point to the possibility of addressing spatially localized memory formations and moving these memory bits along the medium in a controllable fashion.

viXra, 2016

A friendly debate between the authors characterizes one that is prevalent among the community of ‘dissident’ physicists who do not accept Einstein’s relativity as the final explanation for the behavior of light. They wonder whether or not light acquires the velocity of its source. Maxwell’s equations strongly suggest a fixed speed for light upon its emission from a source. Is the emission point fixed in space? Would motion of the emitter alter the trajectory (and speed?) of the emitted light? Light’s immense speed makes determining this extremely difficult to answer on a scale less than astronomical. For example, despite supposed ‘definitive’ proof that there is no aether and light speed is universally constant alleged by proponents of a ‘null’ result from the 1887 Michelson-Morley Interferometer Experiment, debate continues over both of these subjects. The authors propose experiments using current technology that might be able to offer a definitive resolution to this debate, or pos...

Journal of Experimental and Theoretical Physics Letters, 2000

Arxiv preprint physics/0703271, 2007

Physical Review Letters, 2001

The atoms moving within the waveguide with a critical frequency higher than the resonant frequency of atoms are suggested for obtaining the "slow light". Due to the absence of the resonant mode in the guide the atoms conserves excitation and coherence. The speed of this mixed excitation (electromagnetic field + moving atom) can be very low or even zero.

Physical Review A, 2012

A novel technique of atom slowing is proposed. It is based upon the dispersive interaction of atoms with optical potential pulses generated by a far off-resonance standing wave modulated in time. Each pulse reduces the velocity by a small amount. By repeating the process thousands of times, the velocity can be lowered from several hundreds m/s down to almost zero, over a path as short as 20 cm. In absence of any random recoil process, the initial characteristics of the beam are preserved.

Cornell University - arXiv, 2011

We admit that the vacuum is not empty but is filled with continuously appearing and disappearing virtual fermion pairs. We show that if we simply model the propagation of the photon in vacuum as a series of transient captures within the virtual pairs, we can derive the finite light velocity c as the average delay on the photon propagation. We then show that the vacuum permittivity ǫ 0 and permeability µ 0 originate from the polarization and the magnetization of the virtual fermions pairs. Since the transit time of a photon is a statistical process within this model, we expect it to be fluctuating. We discuss experimental tests of this prediction. We also study vacuum saturation effects under high photon density conditions.