Showing papers by "Robert W. Boyd published in 2004"
TL;DR: In this article, a cancellation of absorption occurs on resonance for two (or any even number of) coupled optical resonators, due to mode splitting and classical destructive interference, particularly when the resonator finesse is large and the loss in resonator farthest from the excitation waveguide is small.
Abstract: We demonstrate that a cancellation of absorption occurs on resonance for two (or any even number of) coupled optical resonators, due to mode splitting and classical destructive interference, particularly when the resonator finesse is large and the loss in the resonator farthest from the excitation waveguide is small. The linewidth and group velocity of a collection of such coupled-resonator structures may be decreased by using larger resonators of equal size, by using larger resonators of unequal size where the optical path length of the larger resonator is an integer multiple of that of the smaller one, or by using a larger number of resonators per structure. We explore the analogy between these effects and electromagnetically-induced transparency in an atomic system.
461 citations
TL;DR: A momentum-position realization of the EPR paradox is reported on using direct detection in the near and far fields of the photons emitted by collinear type-II phase-matched parametric down conversion to achieve a measured two-photon momentum- position variance product of 0.01 variant Planck's over 2pi (2).
Abstract: We report on a momentum-position realization of the EPR paradox using direct detection in the near and far fields of the photons emitted by collinear type-II phase-matched parametric down conversion. Using this approach we achieved a measured two-photon momentum-position variance product of $0.01{\ensuremath{\hbar}}^{2}$, which dramatically violates the bounds for the EPR and separability criteria.
435 citations
TL;DR: It is found that entangled photons allow high-contrast, high-resolution imaging to be performed at any distance from the light source, and is demonstrated by forming ghost images in the near and far fields of an entangled photon source.
Abstract: Coincidence, or ghost, imaging is a technique that uses two correlated optical fields to form an image of an object. In this work we identify aspects of coincidence imaging which can be performed with classically correlated light sources and aspects which require quantum entanglement. We find that entangled photons allow high-contrast, high-resolution imaging to be performed at any distance from the light source. We demonstrate this fact by forming ghost images in the near and far fields of an entangled photon source, noting that the product of the resolutions of these images is a factor of 3 better than that which is allowed by classical diffraction theory.
322 citations
TL;DR: In this paper, an experimental investigation of the transfer characteristics of a fiber ring resonator for various values of the resonator finesse was carried out to measure the spectral dependence of the intensity transmission and the induced phase shift in the undercoupled, critically coupled, and overcoupled regimes.
Abstract: We present the results of an experimental investigation of the transfer characteristics of a fiber ring resonator for various values of the resonator finesse. In particular, we measure the spectral dependence of the intensity transmission and the induced phase shift in the undercoupled, critically coupled, and overcoupled regimes. We also demonstrate tunable optical (true time) group delay via a fiber ring resonator and show that a high finesse is unnecessary. Our laboratory results are in excellent agreement with theoretical predictions.
238 citations
TL;DR: A new type of artificial nonlinear optical material composed of a one-dimensional metal-dielectric photonic crystal which displays a strongly enhanced non linear optical response (up to 12X) in transmission is described.
Abstract: We describe a new type of artificial nonlinear optical material composed of a one-dimensional metal-dielectric photonic crystal. Because of the resonant nature of multiple Bragg reflections, the transmission within the transmission band can be quite large, even though the transmission through the same total thickness of bulk metal would be very small. This procedure allows light to penetrate into the highly nonlinear metallic layers, leading to a large nonlinear optical response. We present experimental results for a $\mathrm{C}\mathrm{u}/{\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ crystal which displays a strongly enhanced nonlinear optical response (up to $12X$) in transmission.
196 citations
TL;DR: In this article, four archetypal geometries consisting of effectively one-dimensional sequences of coupled micro-resonators are considered, and two of these cases exhibit distributed feedback such as is found in a traditional multilayered structure supporting photonic bandgaps.
Abstract: Sequences of optical microresonators can be used to construct densely integrated structures that display slow group velocity, ultrahigh or low dispersion of controllable sign, enhanced self-phase modulation, and nonlinear optical switching. We consider four archetypal geometries consisting of effectively one-dimensional sequences of coupled microresonators. Two of these cases exhibit distributed feedback such as is found in a traditional multilayered structure supporting photonic bandgaps. The other two exhibit localized feedback and resonant enhancement but are free from photonic bandgaps. All of these structures offer unique properties useful for controlling the propagation of light pulses on a chip.
130 citations
TL;DR: It is shown that the origin of the enhancement of third-harmonic generation in 3D polystyrene-air photonic crystals pumped by a near infrared laser beam is phase matching provided by the periodic structure of thephotonic crystals.
Abstract: We have observed a dramatic enhancement of third-harmonic generation in 3D polystyrene-air photonic crystals pumped by a near infrared laser beam. As the pump wavelength is tuned, the peak of the enhancement occurs when the third-harmonic wavelength approaches the short-wavelength edge of the band gap. We show that the origin of the enhancement is phase matching provided by the periodic structure of the photonic crystals.
97 citations
TL;DR: In these experiments, an N-photon-absorption recording medium is simulated by Nth harmonic generation followed by a CCD camera, suggesting that the improved resolution achieved through use of "quantum lithography" results primarily from the nonlinear response of the recording medium and not from quantum features of the light field.
Abstract: A nonlinear optical, interferometric method for improving the resolution of a lithographic system by an arbitrarily large factor with high visibility is described. The technique is implemented experimentally for both two-fold and three-fold enhancement of the resolution with respect to the traditional Rayleigh limit. In these experiments, an N-photon-absorption recording medium is simulated by Nth harmonic generation followed by a CCD camera. This technique does not exploit quantum features of light; this fact suggests that the improved resolution achieved through use of “quantum lithography” results primarily from the nonlinear response of the recording medium and not from quantum features of the light field.
86 citations
16 May 2004
TL;DR: In this paper, a 5 micron radius optical micro-ring resonator in AlGaAs has been constructed and characterized, which displays an enhanced nonlinear phase response at a length scale 100 times smaller than an ordinary AlgaAs waveguide.
Abstract: We have constructed and characterized a 5 micron radius optical micro-ring resonator in AlGaAs. The device displays an enhanced nonlinear phase response at a length scale 100 times smaller than an ordinary AlGaAs waveguide
76 citations
TL;DR: Treating the sodium vapor as a Doppler broadened two-level atomic system, it is found that it can accurately model the propagation and breakup of these beams with numerical simulations and experimentally shows that vortex beams with m values of 1, 2, and 3 tend to break into two, four, and six filaments.
Abstract: We have observed filamentation due to azimuthal modulational instabilities in spinning ring solitons with orbital angular momentum m variant Planck's over 2pi in sodium vapor. We show experimentally that vortex beams with m values of 1, 2, and 3 tend to break into two, four, and six filaments, respectively. Treating the sodium vapor as a Doppler broadened two-level atomic system, we find that we can accurately model the propagation and breakup of these beams with numerical simulations.
73 citations
TL;DR: In this paper, it was shown that the atomic states can be described by wavefunctions calculated in the absence of an electromagnetic field when using the d · E (but not the p · A) form of the interaction Hamiltonian.
Abstract: The interaction of an atomic system with an externally applied electromagnetic field can be treated in the electric dipole approximation by means of either the minimal coupling (p · A) or direct coupling (d · E) Hamiltonian. It is shown that both methods lead to identical and unambiguous predictions for observable quantities as long as the atomic wavefunctions are transformed when used in the minimal-coupling formulation. The physical meaning of kinetic momentum is used to show that the atomic states must be described by wavefunctions calculated in the absence of an electromagnetic field when using the d · E (but not the p · A) form of the interaction Hamiltonian. When, however, observables are calculated using the common approximations of resonance atomic physics – the two-level approximation and the rotatingwave approximation – the two formulations can lead to measurably different results. This point is illustrated by calculating the induced polarization (and hence the refractive index) of an a...
TL;DR: In this article, coherent Stokes and anti-Stokes Raman scattering influence coherent population trapping in an atomic sodium vapor cell and induced transparency, induced absorption, and gain features, all of subnatural linewidth.
Abstract: We study how coherent Stokes and anti-Stokes Raman scattering influence coherent population trapping. In an experiment using an atomic sodium vapor cell we observe induced transparency, induced absorption, and gain features, all of subnatural linewidth. The electromagnetically induced resonance is a peak or a dip depending on which side of the optical transition the fields are tuned to, and thus whether coherent anti-Stokes Raman scattering or coherent Stokes Raman scattering is the dominant process.
TL;DR: In this article, a single terrylene molecule embedded in a cholesteric-liquid-crystal host is used to demonstrate operation of a room-temperature single-photon source.
Abstract: Fluorescence antibunching from single terrylene molecules embedded in a cholesteric-liquid-crystal host is used to demonstrate operation of a room-temperature single-photon source. One-dimensional (1-D) photonic-band-gap microcavities in planar-aligned cholesteric liquid crystals with band gaps from visible to near-infrared spectral regions are fabricated. Liquid-crystal hosts (including liquid crystal oligomers and polymers) increase the source efficiency, firstly, by aligning the dye molecules along the direction preferable for maximum excitation efficiency (deterministic molecular alignment provides deterministically polarized output photons), secondly, by tuning the 1-D photonic-band-gap microcavity to the dye fluorescence band and thirdly, by protecting the dye molecules from quenchers, such as oxygen. In our present experiments, using oxygen-depleted liquid-crystal hosts, dye bleaching is avoided for periods exceeding one hour of continuous 532 nm excitation.
TL;DR: In this article, the authors show that there is a dependence of the nonresonant contribution on the damping and that damping enters according to the ''opposite sign prescription''.
Abstract: Motivated by recent discussions concerning the manner in which damping appears in the electric polarizability, we show that (a) there is a dependence of the nonresonant contribution on the damping and that (b) the damping enters according to the ``opposite sign prescription.'' We also discuss the related question of how the damping rates in the polarizability are related to energy-level decay rates.
TL;DR: A review of the current techniques used for generating ultra-slow, superluminal, and even stopped light can be found in this article, where coherent population oscillations can be used to produce ultraslow and super-light under these conditions.
Abstract: Slow and superluminal group velocities can be observed in any material that has large normal or anomalous dispersion. While this fact has been known for more than a century, recent experiments have shown that the dispersion can be very large without dramatically deforming a pulse. As a result, the significance and nature of pulse velocity is being reevaluated. In this review, we discuss some of the current techniques used for generating ultra-slow, superluminal, and even stopped light. While ultra-slow and superluminal group velocities have been observed in complicated systems, from an applications point of view it is highly desirable to do have this done in a solid that can operate at room temperature. We describe how coherent population oscillations can produce ultra-slow and superluminal light under these conditions.
TL;DR: In this paper, the authors survey some recent research on polarization aspects of nonlinear optical interactions in chiral isotropic optical materials and analyze some of the conflicting statements that have recently been made in the scientific literature.
Abstract: Polarization effects play an even more important role in nonlinear optics than in linear optics because of the richer set of phenomena describable by higher-order tensor relations. The present contribution surveys some recent research on polarization aspects of nonlinear optical interactions, paying special attention to nonlinear optical interactions in chiral isotropic optical materials. We especially address the question of the existence of a linear electro-optic effect in chiral isotropic materials and analyse some of the conflicting statements that have recently been made in the scientific literature.
TL;DR: Porous CdSe layers have been produced by anodic etching of crystalline substrates in a HCl solution as discussed by the authors, and gain of luminescence was observed in some porous regions and attributed to the formation of ring microcavities for light in the porous network.
Abstract: Porous CdSe layers have been produced by anodic etching of crystalline substrates in a HCl solution. Anodization under in situ UV illumination resulted in the formation of uniformly distributed parallel pores with a diameter of 30 nm, stretching perpendicularly to the initial surface. At the same time, pronounced nonuniformities in the spatial distribution of pores were evidenced in samples subjected to anodic etching in the dark. Gain of luminescence was observed in some porous regions and attributed to the formation of ring microcavities for light in the porous network.
Patent•
09 Jan 2004TL;DR: In this article, a deterministically polarized single photon using liquid-crystal hosts of either monomeric or oligomeric/polymeric form to preferentially align the single emitters for maximum excitation efficiency is presented.
Abstract: An efficient technique for producing deterministically polarized single photons uses liquid-crystal hosts of either monomeric or oligomeric/polymeric form to preferentially align the single emitters for maximum excitation efficiency. Deterministic molecular alignment also provides deterministically polarized output photons; using planar-aligned cholesteric liquid crystal hosts as 1-D photonic-band-gap microcavities tunable to the emitter fluorescence band to increase source efficiency, using liquid crystal technology to prevent emitter bleaching. Emitters comprise soluble dyes, inorganic nanocrystals or trivalent rare-earth chelates.
TL;DR: Ruchon et al. as discussed by the authors isolated the magnetochiral refraction in Pasteur's tartrates and deduced the associated magnet-ochiral absorption, showing that the first attempt to induce chirality with a magnetic field could perhaps have succeeded, provided that a UV source was simultaneously used.
01 Jan 2004
TL;DR: In this paper, the magnetochiral refraction in tartrates has been isolated and the associated magnetochirality has been deduced, showing that the first attempt to induce chirality with a magnetic field could perhaps have succeeded, provided that a UV source was simultaneously used.
Abstract: We have isolated the magnetochiral refraction in Pasteur’s tartrates and deduced the associated magnetochiral absorption. The presence of a strong peak at 235 nm in the magnetochiral absorption spectrum of tartrates shows that Pasteur’s first attempt to induce chirality with a magnetic field could perhaps have su cceeded, provided that a UV source was simultaneously used. To
20 Dec 2004
TL;DR: An overview of recent research aimed at controlling the propagation velocity of light pulses through material systems is presented in this article, where two basic approaches have been successfully pursued in recent years: quantum coherence effects, such as electromagnetically induced transparency or coherent population oscillations, to modify the material response at an atomic level.
Abstract: An overview of recent research aimed at controlling the propagation velocity of light pulses through material systems is presented. Most of the research involves two basic approaches. One approach is to make use of quantum coherence effects, such as electromagnetically induced transparency or coherent population oscillations, to modify the material response at an atomic level. Another approach is to form artificial material, such as photonic crystals, that possess strong dispersive properties which lead to a large modification to the group velocity. Both of these approaches have been successfully pursued in recent years.
16 May 2004
TL;DR: In this paper, a single photon source based on fluorescence from single-dye molecules in liquid-crystal hosts manifests itself in observed dye-fluorescence antibunching, which increases the source efficiency using dyes/colloidal-quantum-dots as emitters.
Abstract: A single photon source based on fluorescence from single-dye molecules in liquid-crystal hosts manifests itself in observed dye-fluorescence antibunching. 400 to 2200-nm, liquid-crystal 1-D-photonic-bandgap structures will increase the source efficiency using dyes/colloidal-quantum-dots as emitters
TL;DR: In this paper, the authors used pump and probe fields to induce ground-state chromium ions to oscillate coherently at the resulting beat frequency, leading to a decreased absorption of the probe beam, and consequently a steep spectral variation of the refractive index with a positive slope.
Abstract: In recent years there has been great interest in techniques that can lead to a modification of the propagation velocity of light pulses through optical materials [1,2]. Interest stems both from the intrinsic interest in the ability to control the velocity of light over large ranges and from the potential for applications such as controllable delay lines, optical data storage devices, optical memories, and devices for quantum information. Much of this recent work has made use of the process [3] of electromagnetically induced transparency (EIT) to modify the absorptive and refractive properties of a material both to produce the good transparency needed to propagate pulses over long distances and to produce a rapid variation of refractive index needed to produce slow light. We have recently introduced a new method for achieving ultra-slow light propagation [4]. Our method produces slow light in room temperature solids. Like EIT, our method makes use of the concept of quantum coherence, but uses a different effect known as coherent population oscillations [5,6]. In particular, we apply pump and probe fields to our ruby crystal, and the population of ground-state chromium ions is induced to oscillate coherently at the resulting beat frequency. These oscillations lead to a decreased absorption of the probe beam, and consequently (by the Kramers-Kronig relations) to a steep spectral variation of the refractive index with a positive slope. Since the group index is given by n n dn d g = + ω ω / , this process produces a large positive value of the group index. We have also studied light propagation in alexandrite [7], which at certain wavelengths acts as an inverse saturable absorber. In this case, coherent population oscillations lead to increased absorption of the probe beam and consequently a steep variation of the refractive index with negative slope and thus a negative value of the group
TL;DR: In this paper, a pump-power-tunable slow and superluminal pulse propagation at room temperature in an erbium-doped fiber amplifier was demonstrated, obtaining signal group velocities as slow as 19,000 m/s and as fast as -16,000m/s.
Abstract: We demonstrate pump-power-tunable slow and superluminal pulse propagation at room temperature in an erbium-doped fiber amplifier. Signal pulses at 1550 nm were sent through an EDF with various pump intensities, obtaining signal group velocities as slow as 19,000 m/s and as fast as -16,000 m/s.
TL;DR: In this paper, the authors constructed and characterized several optical micro-ring Resonators with scale sizes of the order of 10 microns, which are intended to serve as building blocks for engineerable linear and nonlinear photonic media.
Abstract: Microring resonators can serve as key elements in the realization
of engineerable photonic media. A sequence of resonators coupled
to an optical waveguide can be viewed as an optical transmission
line with highly controllable dispersive and nonlinear properties,
similar to those of photonic crystals or gratings. We have
constructed and characterized several optical micro-ring
resonators with scale sizes of the order of 10 microns. These
devices are intended to serve as building blocks for engineerable
linear and nonlinear photonic media. Light is guided vertically by
an epitaxially grown structure and transversely by deeply etched
air-clad sidewalls. In this work, we chose to construct ring
resonators in AlGaAs and probe them at a photon energy below the
half-gap of the material. Our motivation for this choice was to
maximize the ultrafast bound (Kerr) nonlinearities resulting from
virtual transitions while minimizing the two-photon contribution
to carrier generation. We report on the spectral phase transfer
characteristics of such resonators. We also report the observation
of a pi-radian Kerr nonlinear phase shift accumulated in a single
compact ring resonator evidenced by all-optical switching between
output ports of a resonator-enhanced Mach-Zehnder interferometer.
TL;DR: An exact theoretical model describing third harmonic generation in 1D photonic crystals has been developed in this paper, which employs the transfer matrix method and accounts for material and structural dispersion Experimental results for THG in a 1D polymer-dispersed liquid crystal grating are in good agreement with the model.
Abstract: An exact theoretical model describing third harmonic generation in 1D photonic crystals has been developed The model employs the transfer matrix method and accounts for material and structural dispersion Experimental results for THG in a 1D polymer-dispersed liquid crystal grating are in good agreement with the model Full-text article is not available
02 Aug 2004
TL;DR: In this article, the authors have observed ultralow and superluminal propagation in alexandrite enabled by the process of coherent population oscillations, where the velocity of light can be controlled.
Abstract: We have observed ultraslow propagation in ruby and superluminal propagation in alexandrite enabled by the process of coherent population oscillations. Novel applications are allowed by the ability to control the velocity of light.
28 Mar 2004
TL;DR: In this article, the phase transfer characteristics and all-optical switching in optical micro-ring resonators were characterized and constructed and characterized photonic devices with epitaxially grown layers and air-clad sidewalls.
Abstract: We have constructed and characterized photonic devices based on optical micro-ring resonators. Light is guided by epitaxially grown layers and by air-clad sidewalls. We describe the phase transfer characteristics and all-optical switching in these devices.