Showing papers on "Slow light published in 2004"
TL;DR: The design, fabrication, and measurement of photonic-band-gap waveguides, resonators and their coupled elements in two-dimensional photonic crystal (PhC) slabs have been investigated and a large group delay is observed by time-domain measurement.
Abstract: The design, fabrication, and measurement of photonic-band-gap (PBG) waveguides, resonators and their coupled elements in two-dimensional photonic crystal (PhC) slabs have been investigated. We have studied various loss mechanisms in PBG waveguides and have achieved a very low propagation loss (~1 dB/mm). For these waveguides, we have observed a large group delay (>100 ps) by time-domain measurement. As regards PBG resonators, we realize very high-Q and small volume resonators in PhC slabs by appropriate design. Finally, we demonstrate various forms of coupled elements of waveguides and resonators: 2-port resonant-tunneling transmission devices, 4-port channel-drop devices using the slow light mode, and 3-port channel-drop devices using the resonant-tunneling process.
451 citations
01 Mar 2004
TL;DR: In this article, the authors demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time and infer group velocity as low as 9600 m/s from the experimentally measured dispersive characteristics.
Abstract: We demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time. A group velocity as low as 9600 m/s is inferred from the experimentally measured dispersive characteristics. The transparency window exhibits a bandwidth as large as 2 GHz.
286 citations
TL;DR: In this article, the authors demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time and infer group velocity as low as 9600 m/s from the experimentally measured dispersive characteristics.
Abstract: We demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time. A group velocity as low as 9600 m/s is inferred from the experimentally measured dispersive characteristics. The transparency window exhibits a bandwidth as large as 2 GHz.
264 citations
Book•
30 Nov 2004TL;DR: In this article, the authors focus on how refractive index can vary with frequency in such a way that the group velocities of optical pulses can be much greater or much smaller than the speed of light in vacuum.
Abstract: The propagation of light in dispersive media is a subject of fundamental as well as practical importance. In recent years attention has focused in particular on how refractive index can vary with frequency in such a way that the group velocities of optical pulses can be much greater or much smaller than the speed of light in vacuum, or in which the refractive index can be negative. Treating these topics at an introductory to intermediate level, Fast Light, Slow Light and Left-Handed Light focuses on the basic theory and describes the significant experimental progress made during the past decade. The book pays considerable attention to the fact that superluminal group velocities are not in conflict with special relativity and to the role of quantum effects in preventing superluminal communication and violations of Einstein causality. It also explores some of the basic physics at the opposite extreme of very slow group velocities as well as stopped and regenerated light, including the concepts of electromagnetically induced transparency and dark-state polaritons. Another very active aspect of the subject discussed concerns the possibility of designing metamaterials in which the refractive index can be negative and propagating light is left-handed in the sense that the phase and group velocities are in opposite directions. The last two chapters are an introduction to some of the basic theory and consequences of negative refractive index, with emphasis on the seminal work carried out since 2000. The possibility that "perfect" lenses can be made from negative-index metamaterials-which has been perhaps the most controversial aspect of the field-is introduced and discussed in some detail.
195 citations
TL;DR: A microscopic theory for the interplay between light and matter is presented and it is shown how the slow light can provide an effective magnetic field acting on the electrically neutral fermions, a direct analogy of the free electron gas in an uniform magnetic field.
Abstract: We investigate the effect of slow light propagating in a degenerate atomic Fermi gas. In particular we use slow light with an orbital angular momentum. We present a microscopic theory for the interplay between light and matter and show how the slow light can provide an effective magnetic field acting on the electrically neutral fermions, a direct analogy of the free electron gas in an uniform magnetic field. As an example we illustrate how the corresponding de Haas-van Alphen effect can be seen in a neutral gas of fermions.
148 citations
TL;DR: An experimental study of resonant six-wave mixing in coherently prepared Rb atoms finds that electromagnetically induced transparency in a four-level atomic system suppresses the linear susceptibility and enhances the nonlinear susceptibilities, which leads to the resonantly enhanced, slow-photon six- wave mixing at low light intensities.
Abstract: We report an experimental study of resonant six-wave mixing in coherently prepared Rb atoms. Electromagnetically induced transparency in a four-level atomic system suppresses the linear susceptibility and enhances the nonlinear susceptibilities, which leads to the resonantly enhanced, slow-photon six-wave mixing at low light intensities. The light emission in the six-wave mixing process can be viewed as resulting from diffraction of slow light off a resonant nonlinear grating induced in the four-level system by a standing-wave pump field.
128 citations
TL;DR: It is demonstrated that Aharonov-Albert-Vaidman weak values have a direct relationship with the response function of a system, and have a much wider range of applicability in both the classical and quantum domains than previously thought.
Abstract: We demonstrate that Aharonov-Albert-Vaidman weak values have a direct relationship with the response function of a system, and have a much wider range of applicability in both the classical and quantum domains than previously thought. Using this idea, we have built an optical system, based on a birefringent photonic crystal, with an infinite number of weak values. In this system, the propagation speed of a polarized light pulse displays both superluminal and slow light behavior with a sharp transition between the two regimes. We show that this system's response possesses two-dimensional, vortex-antivortex phase singularities. Important consequences for optical signal processing are discussed.
112 citations
TL;DR: In this paper, a variable semiconductor optical buffer based on the electromagnetically induced transparency in a quantum dot waveguide is theoretically investigated with feasible parameters for applications to a 40 Gbps optical network.
Abstract: A variable semiconductor optical buffer based on the electromagnetically induced transparency in a quantum dot waveguide is theoretically investigated with feasible parameters for applications to a 40 Gbps optical network. We show the refractive index and absorption spectra of the quantum dot waveguide at various pump levels, which exhibit an optimal pump power for maximum slow-down factor, in agreement with the previous experimental observation using a Pr-doped solid. The group velocity slow-down factor is theoretically analysed as a function of the pump intensity at different broadened linewidths. Inhomogeneous broadening in self-assembled quantum dots degrades the slow-down factor. In order to reduce the inhomogeneous broadening effects, we propose to use a resonant microcavity structure with quantum dots embedded in the active layer to enhance the slow-down factor.
100 citations
TL;DR: It is shown that the group index strongly depends on the number of cavities in the system, especially for operation at the center frequency, and the nonlinear phase sensitivity shows an enhancement proportional to the square of the groupIndex.
Abstract: In this paper, we derive the exact dispersion relation of one dimensional periodic coupled-resonator optical waveguides of finite length, from which the reduced group velocity of light is obtained. We show that the group index strongly depends on the number of cavities in the system, especially for operation at the center frequency. The nonlinear phase sensitivity shows an enhancement proportional to the square of the group index (or light slowing ratio). Aperiodic coupled ring-resonator optical waveguides with optimized linear properties are then synthesized to give an almost ideal nonlinear phase shift response. For a given application and bandwidth requirement, the nonlinear sensitivity can be increased by either decreasing resonator length or by using higher-order structures. The impact of optical loss, including linear and two-photon absorption is discussed in post-analysis.
97 citations
TL;DR: In this article, the radiation pressure on the surface of a waveguide formed by omnidirectionally reflecting mirrors was studied and it was shown that in the absence of losses, the pressure goes to infinity as the distance between the mirrors is reduced to the cutoff separation of the waveguide mode.
Abstract: We study the radiation pressure on the surface of a waveguide formed by omnidirectionally reflecting mirrors. In the absence of losses, the pressure goes to infinity as the distance between the mirrors is reduced to the cutoff separation of the waveguide mode. This divergence at constant power input is due to the reduction of the modal group velocity to zero, which results in the magnification of the electromagnetic field. Our structure suggests a promising alternative, microscale system for observing the variety of classical and quantum-optical effects associated with radiation pressure in Fabry–Perot cavities.
72 citations
TL;DR: In this paper, the authors reported an experimental observation of resonant four-wave mixing in cold Rb atoms, which is a type of slow-light four wave mixing at low light intensities.
Abstract: Electromagnetically induced transparency in a four-level atomic system suppresses the linear susceptibility and enhances the nonlinear susceptibilities, which leads to the resonantly enhanced slow-light four-wave mixing at low light intensities. We report an experimental observation of such resonant four-wave mixing in cold Rb atoms.
TL;DR: In this article, the optical properties of line-defect waveguides in two-dimensional photonic crystal slabs were investigated using picosecond light pulses using an autocorrelation method.
Abstract: The optical properties of line-defect waveguides in two-dimensional photonic crystal slabs are investigated using picosecond light pulses. Time-domain waveforms of the light pulse propagating through the waveguide are successfully observed using an autocorrelation method. The group velocity of the waveguide is directly determined from the group delay time for light pulses reflected back and forth along the waveguide. A small group velocity of one-twentieth the speed of light in vacuum is observed at a frequency near the edge of the waveguide mode. The frequency dependence of the group velocity is also measured, and the group-velocity dispersion is found to be larger than that of normal single-mode optical fibers by a factor of 104–105.
TL;DR: In this article, the group velocity of a light pulse propagating through a four-level system exhibiting electromagnetically induced transparency can be manipulated by a pump laser, which induces the large optical nonlinearities with steep normal or anomalous dispersion.
Abstract: The group velocity of a light pulse propagating through a four-level system exhibiting electromagnetically induced transparency can be manipulated by a pump laser. The pump laser induces the large optical nonlinearities with steep normal or anomalous dispersion. We present experimental measurements that demonstrate both slow and superluminal light propagation in cold Rb atoms.
01 May 2004
TL;DR: In this paper, the authors reported an experimental observation of resonant four-wave mixing in cold Rb atoms, which is a type of slow-light four wave mixing at low light intensities.
Abstract: Electromagnetically induced transparency in a four-level atomic system suppresses the linear susceptibility and enhances the nonlinear susceptibilities, which leads to the resonantly enhanced slow-light four-wave mixing at low light intensities. We report an experimental observation of such resonant four-wave mixing in cold Rb atoms.
17 Jun 2004
TL;DR: In this paper, the authors proposed a compact variable all-optical buffer using slow-light in semiconductor nanostructures, which is achieved by slowing down the optical signal using an external control light source to vary the dispersion characteristic of the medium via electromagnetically induced transparency effect.
Abstract: We proposed a compact variable all-optical buffer using slow-light in semiconductor nanostructures. We discuss the general design principle via dispersion engineering. The buffering effect is achieved by slowing down the optical signal using an external control light source to vary the dispersion characteristic of the medium via electromagnetically induced transparency effect. We demonstrate that the semiconductor quantum dot structures can be used as a slow-light medium. In such structure, the total buffering time is variable and controlled by an external pump laser. We present a theoretical investigation of the criteria for achieving slow light in semiconductor quantum dots. New pump scheme is proposed to overcome the sample nonuniformity. Finally, optical signal propagation through the semiconductor optical buffer is presented to demonstrate the feasibility for practical applications.
TL;DR: In this article, the authors investigate properties of hybrid systems of Photonic Crystal micro-cavities which incorporate a highly non-linear ultra slow light medium, and demonstrate that such systems, while being miniature in size (order wavelength), and integrable, could enable ultra-fast nonlinear all-optical switching at single photon energy levels.
Abstract: Using analytical modeling and detailed numerical simulations, we investigate properties of hybrid systems of Photonic Crystal micro-cavities which incorporate a highly non-linear Ultra Slow Light medium. We demonstrate that such systems, while being miniature in size (order wavelength), and integrable, could enable ultra-fast non-linear all-optical switching at single photon energy levels.
TL;DR: In this article, the authors developed a theoretical model for slow light using excitonic population oscillation in a semiconductor quantum well in a two-level system, where the resonant pump and the signal have a difference frequency within the range of inverse of the carrier lifetime, coherent population beating at this frequency will be generated.
Abstract: We develop a theoretical model for slow light using excitonic population oscillation in a semiconductor quantum well In a two-level system, if the resonant pump and the signal have a difference frequency within the range of inverse of the carrier lifetime, coherent population beating at this frequency will be generated We analyze the excitonic population oscillation using an atomiclike model extended from semiconductor Bloch equations for both spin subsystems of the excitonic population and the electrical polarization density The two spin subsystems are coupled by the excitation-induced dephasing rate, which depends on the net population difference in conduction and heavy hole quantized bands and the population exchange due to flip of the spins of electrons or holes We present our theoretical results for the absorbance, the refractive index spectra, and the slowdown factor due to population oscillation at various pump intensities, and show very good agreement with experimental data It is shown that a slowdown factor of $312\ifmmode\times\else\texttimes\fi{}{10}^{4}$ has been achieved for a semiconductor quantum-well structure We also obtain analytical solutions from our theory and account for different response behaviors of the signal when its polarization is either parallel or orthogonal to that of the pump, which has also been confirmed by experiments
TL;DR: In this article, a simple experimental system is presented in which the group velocity of acoustic wave packets traveling in an air-filled waveguide can be slowed to values much smaller than the speed of sound in air.
Abstract: A simple experimental system is presented in which the group velocity of acoustic wave packets traveling in an air-filled waveguide can be slowed to values much smaller than the speed of sound in air. The experiment is an acoustic analog of the much-studied optical phenomenon of slow light propagation. Slow (or even stopped) light propagation has been observed in atomic vapors in the vicinity of strong dispersion, typically associated with electromagnetically induced transparency. In the acoustic experiment described here, strong dispersion is produced by the introduction of a defect in an otherwise perfectly periodic one-dimensional acoustic band gap array. The defect produces a narrow transmission band within the forbidden acoustic band gap region resulting in strong dispersion. By tuning the carrier frequency of the acoustic wave packet to the peak transmission of the defect, the group velocity can be slowed to 0.24vs, where vs is the speed of sound in air. These results are shown to be consistent with...
TL;DR: Thelen's method is used to find the parameters of the matching layer to reduce oscillations on the group Velocity and transmission spectra, and to analyze the structure parameters that determine the bandwidth and the group velocity.
Abstract: We study the finite-size effect on the dispersion relation, group velocity, and transmission curves of one-dimensional finite-size coupled-resonator optical waveguide (CROW) structures. Both the dispersion relation and the group velocity curves of a finite-size CROW oscillate along those of the corresponding infinite-extended ones. The oscillations can be suppressed by matching the equivalent admittance of the surrounding medium to that of the unit cell. Thelen's method is used to find the parameters of the matching layer to reduce oscillations on the group velocity and transmission spectra, and to analyze the structure parameters that determine the bandwidth and the group velocity.
TL;DR: In this paper, the authors describe the use of ultra-slow light pulses to probe superfluidity and the creation of quantized vortices in Bose-Einstein condensates through formation of'superfluid shock.
Abstract: I n 1998, laser pulses were slowed [1] in a Bose-Einstein condensate (BEe) [2] ofsodium to only 17 m/s, more than seven orders of magnitude lower than the speed of light in vacuum. Associated with the dramatic reduction factor for the light speed was a spatial compression of the pulses by the same large factor. A light pulse, which was more than 1 km long in vacuum, was compressed to a size of -50 flm, and at that point was completely contained within the condensate [1]. This allowed the light-slowing experiments to be brought to their ultimate extreme [3]: in the summer of 2000, light pulses were completely stopped, stored, and subsequently revived in an atomic medium, with millisecond storage times [4]. The initial ultra-slow light experiments spurred a flurry of slow light investigations, and slow or partially stopped light has now been observed in limited geometries in warm rubidium vapours [5-7], liquid-nitrogen cooled crystals [8], and recently in room temperature crystals [9]. Here, we begin with a discussion ofultra-slow and stopped light. We describe how cold atoms and Bose-Einstein condensates have been manipulated to generate media with extreme optical properties. While the initial experiments concentrated on the light propagation, we have recently begun a number of investigations of the effects that slow light has on the medium in which it propagates. Effects are profound because both the velocity and length scales associated with propagating light pulses have been brought down to match the characteristic velocity and length scales of the medium. With the most recent extension, the light roadblock [10], we have compressed light pulses to a length ofonly 2 f!ill. Here, we describe the use of ultra-compressed light pulses to probe superfluidity and the creation of quantized vortices in BEes through formation of'superfluid shock. waves'. We also present the observation of an ultra-slow-light-based, pulsed atom laser. Furthermore, we demonstrate the use of slow and stopped light for manipulation of optical information, in particular in Bose-Einstein condensates that allow for phase coherent processing of three-dimensional, compressed patterns of stored optical information.
01 Jan 2004
TL;DR: A group velocity as small as 9600 m/s is inferred from the measured dispersive characteristics, and slow-light via population pulsation in semiconductor quantum well structures is experimentally demonstrated.
Abstract: We demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time. A group velocity as low as 9600 m/s is inferred from the experimentally measured dispersive characteristics. The transparency window exhibits a bandwidth as large as 2 GHz.
TL;DR: In this article, it was shown that inside photonic band gap (PBG) materials the effective index of refraction neff, defined in terms of group velocity, becomes negative in a certain range of frequencies and approaches zero near the photonic-band edge.
Abstract: This paper shows that inside photonic band gap (PBG) materials the effective index of refraction neff, defined in terms of group velocity, becomes negative in a certain range of frequencies. Also, near the photonic-band edge the effective index of refraction neff attains exceptionally high values, which are greater than the refractive indices of the materials (n1 and n2) used. This is related to the anomalous behaviour of group velocity, which becomes negative in a certain range and approaches zero near the photonic-band edge. PBG material with a modified index of refraction has applications in the system of lasing without inversion and can also be used in construction of a perfect lens and other optical devices. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 82–87, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20216
TL;DR: In this article, a simple mathematical model for describing wave propagation through finite slabs of periodic media is provided, and it is proved that only a small part of the energy of the pulse propagates with the speed of light.
Abstract: A simple mathematical model is provided for a description of wave propagation through finite slabs of periodic media. The model concerns the devices of CROW (coupled resonators optical waveguide) type which are widely discussed in physical literature in the last several years. An incident pulse is considered, whose frequency is distributed in a small neighbourhood of a singular frequency for which the dispersion relation of the medium is very flat, and the group velocity (for the infinite medium) is small. It is proved that only a small part of the energy of the pulse propagates with the speed of light. Another part of the energy propagates with the group velocity. The price to pay for this slowdown is the reflection of the majority of the energy of the incident pulse.
TL;DR: In this article, a comprehensive analysis of the optically tunable superprism effect in a two-dimensional nonlinear photonic crystal is presented, and it is shown that, under certain circumstances, if one modifies the band structure of the crystal through the Kerr effect induced by a pump beam, the refraction angle of the transmitted signal beam can be tuned over tens of degrees.
Abstract: A comprehensive analysis of an optically tunable superprism effect in a two-dimensional nonlinear photonic crystal is presented. We demonstrate that, under certain circumstances, if one modifies the band structure of the crystal through the Kerr effect induced by a pump beam, the refraction angle of the transmitted signal beam can be tuned over tens of degrees. Two complementary geometries are considered, namely, air holes in a dielectric background and dielectric rods surrounded by air, and in both cases the TE and TM polarizations are studied. We also show that, because of the slow light effect, in both cases the optical power required to tune the refracted angle is dramatically reduced if the frequency of the pump beam is close to a photonic bandgap edge.
20 Dec 2004
TL;DR: In this paper, a unique characteristic in a simple photonic crystal waveguide, which simultaneously gives the low group velocity and low dispersion, was discovered and used for a dispersion-free optical delay line and various functional devices.
Abstract: We discovered a unique characteristic in a simple photonic crystal waveguide, which simultaneously gives the low group velocity and low dispersion. It will be used for a dispersion-free optical delay line and various functional devices.
TL;DR: In this paper, the influence of ionization on the group velocity and group velocity dispersion was studied for the first time, and inversion of the initial normal dispersion medium at given electron number density was predicted.
Abstract: Influence of ionization on the group velocity and group velocity dispersion is studied for the first time. Inversion of the group velocity dispersion of initially normal dispersion medium at given electron number density is predicted.
TL;DR: In this paper, the authors investigated the reduction of the group velocity due to the steep change of the refractive index caused by coherent population oscillation in a ruby crystal at room temperature.
Abstract: We report the investigation of the reduction of the group velocity propagation resulting from the steep change of the refractive index by the coherent population oscillation in a ruby crystal at room temperature Slow light propagation is observed in a solid-state material at room temperature The measured delay is about 2314±0005 ms, corresponding to a group velocity as slow as 43215±0094 m/s in a non-sinusoid modulated waveform The influences of pulse duration on the delay and the reduction of light propagation are given
TL;DR: In this article, the authors derived formulas of refractive index with the inductor model of electron cloud and the law of energy conservation for light refraction in a medium, that is, the ratio of light speed in vacuum to light speed of light in the medium.
Abstract: Light refraction in a medium results from energy exchange between the medium and the magnetic field of the light. Formulas of refractive index, that is, the ratio of light speed in vacuum to light speed in the medium, were derived with the inductor model of electron cloud and the law of energy conservation. Refractive indices of several media were calculated using the formulas derived and the calculated results are in agreement with the results measured. The anisotropy and the nonlinearity of the refractive index are explained with the theory described in this work.
01 Jan 2004
TL;DR: In this article, Stenner measured the information flow in fast and slow-light OPTICAL PULSE PROPAGATION by measuring the information velocity of the information vector.
Abstract: Physics) MEASUREMENT OF THE INFORMATION VELOCITY IN FASTAND SLOW-LIGHT OPTICAL PULSE PROPAGATION by Michael David Stenner Department of Physics Duke University
TL;DR: In this paper, a four-level system in the Er3+-doped yttrium aluminum garnet crystal that can produce an absorption or gain doublet in the probe absorption spectrum when driven by a coherent field and incoherent pumping was investigated.
Abstract: We investigate a four-level system in the Er3+-doped yttrium aluminum garnet crystal that can produce an absorption or gain doublet in the probe absorption spectrum when driven by a coherent field and incoherent pumping. It is found that the transparent linear positive or negative dispersion can occur between the doublet lines. We show that the group index of a probe pulse can be manipulated when we control the incoherent pumping and the coherent field.