Slow light in semiconductor quantum wells.
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.
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IBM1
TL;DR: An over 300-fold reduction of the group velocity on a silicon chip via an ultra-compact photonic integrated circuit using low-loss silicon photonic crystal waveguides that can support an optical mode with a submicrometre cross-section is experimentally demonstrated.
Abstract: It is known that light can be slowed down in dispersive materials near resonances. Dramatic reduction of the light group velocity-and even bringing light pulses to a complete halt-has been demonstrated recently in various atomic and solid state systems, where the material absorption is cancelled via quantum optical coherent effects. Exploitation of slow light phenomena has potential for applications ranging from all-optical storage to all-optical switching. Existing schemes, however, are restricted to the narrow frequency range of the material resonance, which limits the operation frequency, maximum data rate and storage capacity. Moreover, the implementation of external lasers, low pressures and/or low temperatures prevents miniaturization and hinders practical applications. Here we experimentally demonstrate an over 300-fold reduction of the group velocity on a silicon chip via an ultra-compact photonic integrated circuit using low-loss silicon photonic crystal waveguides that can support an optical mode with a submicrometre cross-section. In addition, we show fast (approximately 100 ns) and efficient (2 mW electric power) active control of the group velocity by localized heating of the photonic crystal waveguide with an integrated micro-heater.
1,307 citations
TL;DR: The physical principles behind the phenomenon of slow light in photonic crystal waveguides, as well as their practical limitations, are discussed and put into context in this paper, including the nature of slow-light propagation, its bandwidth limitation, the scaling of linear and nonlinear interactions with the slowdown factor, issues such as losses, coupling into and the tuning of slow modes.
Abstract: The physical principles behind the phenomenon of slow light in photonic crystal waveguides, as well as their practical limitations, are discussed and put into context This includes the nature of slow light propagation, its bandwidth limitation, the scaling of linear and nonlinear interactions with the slowdown factor as well as issues such as losses, coupling into and the tuning of slow modes Applications in all-optical signal processing appear to be the most promising outcome of the phenomena discussed
627 citations
TL;DR: In this article, the authors present an analysis of optical buffers based on slow-light optical delay lines and show that the minimum achievable size of 1 b is approximately equal to the wavelength of light in the buffer.
Abstract: This paper presents an analysis of optical buffers based on slow-light optical delay lines. The focus of this paper is on slow-light delay lines in which the group velocity is reduced using linear processes, including electromagnetically induced transparency (EIT), population oscillations (POs), and microresonator-based photonic-crystal (PC) filters. We also consider slow-light delay lines in which the group velocity is reduced by an adiabatic process of bandwidth compression. A framework is developed for comparing these techniques and identifying fundamental physical limitations of linear slow-light technologies. It is shown that slow-light delay lines have limited capacity and delay-bandwidth product. In principle, the group velocity in slow-light delay lines can be made to approach zero. But very slow group velocity always comes at the cost of very low bandwidth or throughput. In many applications, miniaturization of the delay line is an important consideration. For all delay-line buffers, the minimum physical size of the buffer for a given number of buffered data bits is ultimately limited by the physical size of each stored bit. We show that in slow-light optical buffers, the minimum achievable size of 1 b is approximately equal to the wavelength of light in the buffer. We also compare the capabilities and limitations of a range of delay-line buffers, investigate the impact of waveguide losses on the buffer capacity, and look at the applicability of slow-light delay lines in a number of applications.
507 citations
TL;DR: A survey of methods for establishing extreme values of the group velocity is presented, concentrating especially on methods that work in room-temperature solids and some applications of slow light.
Abstract: It is now possible to exercise a high degree of control over the velocity at which light pulses pass through material media. This velocity, known as the group velocity, can be made to be very different from the speed of light in a vacuum c. Specifically, the group velocity of light can be made much smaller than c, greater than c, or even negative. We present a survey of methods for establishing extreme values of the group velocity, concentrating especially on methods that work in room-temperature solids. We also describe some applications of slow light.
302 citations
TL;DR: The proposed scheme offers tunable delay in the presence of gain and with a bandwidth which is sufficiently wide to process digital data streams at tens of Gbit/s rates as well as picoseconds pulses.
Abstract: We propose and demonstrate the use of narrow band optical parametric amplification for tunable slow and fast light propagation in optical fibers. The parametric gain is coupled to the Raman process which changes the gain value moderately but modifies the gain spectral shape. Consequently, the delay is enhanced at short wavelengths while it is moderated at long wavelengths. The maximum delay and tuning range can be optimized with respect to each other considering saturation effects in long fibers. The proposed scheme offers tunable delay in the presence of gain and with a bandwidth which is sufficiently wide to process digital data streams at tens of Gbit/s rates as well as picoseconds pulses.
296 citations
References
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TL;DR: Low group velocities of light in an optically dense crystal of Pr doped Y2SiO5 are reported by using a sharp spectral feature in absorption and dispersion that is produced by resonance Raman excitation of a ground-state spin coherence.
Abstract: We report ultraslow group velocities of light in an optically dense crystal of Pr doped ${\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$. Light speeds as slow as 45 m/s were observed, corresponding to a group delay of 66 \ensuremath{\mu}s. Deceleration and ``stopping'' or trapping of the light pulse was also observed. These reductions of the group velocity are accomplished by using a sharp spectral feature in absorption and dispersion that is produced by resonance Raman excitation of a ground-state spin coherence.
791 citations
TL;DR: It is observed that a quantum coherence effect, coherent population oscillations, produces a very narrow spectral "hole" in the homogeneously broadened absorption profile of ruby, which leads to a large value of the group index.
Abstract: We have observed slow light propagation with a group velocity as low as $57.5\ifmmode\pm\else\textpm\fi{}0.5\text{ }\mathrm{m}/\mathrm{s}$ at room temperature in a ruby crystal. A quantum coherence effect, coherent population oscillations, produces a very narrow spectral ``hole'' in the homogeneously broadened absorption profile of ruby. The resulting rapid spectral variation of the refractive index leads to a large value of the group index. We observe slow light propagation both for Gaussian-shaped light pulses and for amplitude modulated optical beams in a system that is much simpler than those previously used for generating slow light.
651 citations
TL;DR: In this article, an all-optical adiabatic and reversible pulse bandwidth compression process was proposed, which can generate arbitrarily small group velocities for any light pulse with a given bandwidth, without any coherent or resonant light-matter interactions.
Abstract: We show that light pulses can be stopped and stored coherently, with an all-optical adiabatic and reversible pulse bandwidth compression process. Such a process overcomes the fundamental bandwidth-delay constraint in optics and can generate arbitrarily small group velocities for any light pulse with a given bandwidth, without any coherent or resonant light-matter interactions. We exhibit this process in optical resonators, where the bandwidth compression is accomplished only by small refractive-index modulations performed at moderate speeds.
566 citations
TL;DR: The dispersive properties of the atomic transition in the rubidium line are measured and this ladder-type system is observed to exhibit electromagnetically induced transparency together with a rapidly varying refractive index.
Abstract: The dispersive properties of the atomic transition in the rubidium ${D}_{2}$ line ($5{S}_{\frac{1}{2}}\ensuremath{-}5{P}_{\frac{3}{2}}$) at 780.0 nm are measured with a Mach-Zehnder interferometer when an additional coupling field at 775.8 nm is applied to an upper transition ($5{P}_{\frac{3}{2}}\ensuremath{-}5{D}_{\frac{5}{2}}$). This ladder-type system is observed to exhibit electromagnetically induced transparency together with a rapidly varying refractive index. A reduction in group velocity for the probe beam (${v}_{g}=\frac{c}{13.2}$) is inferred from the measured dispersion curve with 52.5% suppressed absorption on resonance.
560 citations
01 Nov 2003
TL;DR: A theoretical investigation of the criteria for achieving slow light in semiconductor QDs is presented and a compact variable all-optical buffer using semiconductor quantum dot (QD) structures is proposed and analyzed.
Abstract: A compact variable all-optical buffer using semiconductor quantum dot (QD) structures is proposed and analyzed. 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 an electromagnetically induced transparency effect. We present a theoretical investigation of the criteria for achieving slow light in semiconductor QDs. A QD structure in the presence of strain is analyzed with the inclusion of polarization-dependent intersubband dipole selection rules. Experimental methods to synthesize and the measurements of coherent properties in state-of-the-art QDs are surveyed. Slow-light effects in uniform and nonuniform QDs are compared. Finally, optical signal propagation through the semiconductor optical buffer is presented to demonstrate the feasibility for practical applications.
323 citations