Showing papers on "Optical microcavity published in 2000"

Förster energy transfer in an optical microcavity.

Abstract: By studying the transfer of excitation energy between dye molecules confined within an optical microcavity, we demonstrate experimentally that Forster energy transfer is influenced by the local photonic mode density. Locating donor and acceptor molecules at well-defined positions allows the transfer rate to be determined as a function of both mutual separation and cavity length. The results show that the Forster transfer rate depends linearly on the donor emission rate and hence photonic mode density, providing the potential to control energy transfer by modification of the optical environment.

Efficiency of spontaneous emission from planar microcavities

Abstract: We use a computational model to investigate the different routes by which power is lost by an optical emitter placed in a microcavity environment. We make a quantitative investigation of the 1/2n 2 model used by many workers in evaluating the fraction of power radiated from a thin film of emitting material. We show the limitations of the 1/2n 2 model, emphasizing the important role of the orientation of the dipole moment of the emitters. Multi-layer systems, involving dielectric Bragg stack reflectors and metal mirrors, are compared for their efficiency in producing useful radiation. We consider both a standard Bragg reflector and the recently developed omni-directional Bragg stack. We show that metal mirrors, although lossy, may still be effective for producing useful radiation from microcavities. We focus our attention on parameters appropriate for organic microcavity light emitting diode structures.

Coupling semiconductor nanocrystals to a fused-silica microsphere: a quantum-dot microcavity with extremely high Q factors

Abstract: We demonstrate a quantum-dot microcavity by coupling core–shell semiconductor nanocrystals to a fused-silica microsphere. We show that the composite microcavity can feature Q factors of the order of 108, providing a model system for investigating cavity QED and microlasers at the level of single quantum dots.

Microsphere Integration in Active and Passive Photonics Devices

Abstract: As an important step towards integration of microspheres in compact functional photonics devices, we demonstrate direct efficient coupling of light in and out of high-Q whispering- gallery (WG) modes in silica microspheres using angle- polished single mode fibers. Based on this principle, we present a 1-inch fiber-pigtailed microsphere module that can be used for fiber-optic applications, and a fiber-coupled erbium-doped microsphere laser at 1.55 micrometers . In addition, we report preliminary data on the intensity modulation based on high-Q WG modes in a lithium niobate sphere. We also demonstrate a novel geometry WG-mode optical microcavity that combines Q approximately 107, typical for microspheres, with few-nanometer mode spacing either available in lower quality factor Q approximately 104 microfabricated planar rings.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical properties of multilayered porous silicon

Abstract: We present a short review of some optical devices based on multilayered porous silicon, which can be easily obtained by varying the formation current during the etching process. These include Bragg reflectors and Fabry–Perot microcavities, which can be adjusted from the visible to the near infrared. The interface roughness, tragic in the case of multilayers, is studied. It can be drastically reduced when changing the electrolyte viscosity. The high reflectivities obtained in this way are measured by Cavity Ring–Down Spectroscopy. Problems occurring when realising thin layers and an efficient way to adjust precisely the optical thicknesses of the thin layers constituting the multilayered structure are also presented. Finally we present a method of calculation of the emission which takes absorption into account and is able to explain the angular dependence of the luminescence.

4.8 μm vertical emitting PbTe quantum-well lasers based on high-finesse EuTe/Pb1−xEuxTe microcavities

Abstract: Vertical laser emission at 4.8 μm from PbTe quantum wells in high-finesse Pb0.95Eu0.05Te/EuTe microcavity structures at temperatures between 35 and 85 K is reported. The vertical-cavity laser structure was grown by molecular-beam epitaxy on BaF2(111) substrates, and consisted of a 2λ cavity with four 20 nm quantum wells at the cavity antinodes. Laser emission was excited by optical pumping with a pulsed Nd:YVO4 laser. The comparison of the cavity mode positions with envelope function calculations of the quantum-well energy levels indicates that, in this temperature range, lasing is due to transitions between the ground level of the oblique valleys in the conduction and valence bands.

Cavity-Q-driven spectral shift in a cylindrical whispering-gallery-mode microcavity laser

Abstract: Cavity-Q-driven spectral shift of lasing was observed in a cylindrical microcavity formed by rhodamine6G-doped quinoline in a capillary. The envelope of lasing spectrum showed a blueshift induced by the decreasing cavity Q of whispering gallery modes as the pump fluence increases. The thermally induced refractive index changes were measured from the shifts of individual lasing modes. The observed cavity-Q-driven spectral shift was well described by a simple dye laser model, which accounts for the dependence of cavity Q on the thermally induced refractive index change.

Polariton-biexciton transitions in a semiconductor microcavity

Abstract: Summary form only given. Recent pump-and-probe measurements performed on the exciton-polariton in GaAs-based microcavities have been interpreted in terms of contributions due to biexcitons. Inspired by these initial hints we investigated a microcavity containing a single 5 nm ZnSe quantum well which provides large biexciton binding energies and small exciton linewidths. As a result we report here the first direct observation of a spectrally isolated, pump-induced resonance due to polariton-biexciton transitions in a microcavity.

Optical microcavities using highly luminescent films of semiconductor nanocrystals

Abstract: Colloidally grown CdSe nanocrystals with epitaxial ZnS shells show highly efficient, size-tunable luminescence. We report the incorporation of films of these core-shell nanocrystals into wavelength-scale, high-Q, planar microcavities. Under optical excitation, we find that emission from the nanocrystals couples to the discrete optical modes of the microcavity. The broad free-space emission spectrum of the nanocrystals is modified by the presence of the microcavity, giving a series of sharp emission lines with wavelengths determined by the cavity dimension. Our experiments demonstrate that microcavities with semiconductor emitters can be conveniently fabricated using spin-coating techniques. We find that, at room temperature, the microcavity emission spectrum is independent of excitation intensity for excitation densities up to approximately one electron–hole pair per nanocrystal.

Negatively charged quantum well polaritons in a GaAs/AlAs microcavity: An analog of atoms in a cavity

Abstract: The negatively charged exciton (X-) is observed to strongly couple with the microcavity- (MC-)confined photons in a GaAs quantum well containing a two-dimensional electron gas with 0

Optical enhancement with nanoparticles and microcavities

Abstract: A method and apparatus for enhanced optical emissions, the apparatus comprising a light source (12), a microcavity (14), and a medium comprising nanoparticles, located within or near the microcavity. The nanoparticles are either non-aggregated or are aggregated in the form of fractals. The nanoparticles and microcavity exhibit enhanced linear and non-linear optical parametric oscillation, light detection and ranging, increased sensitivity, high density optical data storage, and near-field optical spectroscopy.

Internal spatial modes in glass microring resonators

Abstract: We have used near-field scanning optical microscopy to measure the internal optical modes inside glass waveguides and microring resonators. The period of the observed standing modes provides a direct measure of the local effective index. The measured effective index and modal shape determines the values of all components of the wave vector. The observed standing modes inside the ring resonator are unexpected, but are caused by the standing modes in the coupling waveguide. Last, we describe a technique that can obtain detailed information about the locations of the dielectric interfaces.

Polariton–acoustic-phonon interaction in a semiconductor microcavity

Abstract: The broadening of polariton lines by acoustic phonons is investigated in a semiconductor microcavity by means of interferometric correlation measurements with subpicosecond resolution. A decrease of the polariton-acoustic phonon coupling is clearly observed for the lower polariton branch as one approaches the resonance between exciton and photon states. This behavior cannot be explained in terms of a semiclassical linear dispersion theory but requires a full quantum description of the microcavity in the strong-coupling regime.

Quasi-monolithic tunable optical resonator

Abstract: An optical resonator has a piezoelectric element attached to a quasi-monolithic structure. The quasi-monolithic structure defines an optical path. Mirrors attached to the structure deflect light along the optical path. The piezoelectric element controllably strains the quasi-monolithic structure to change a length of the optical path by about 1 micron. A first feedback loop coupled to the piezoelectric element provides fine control over the cavity length. The resonator may include a thermally actuated spacer attached to the cavity and a mirror attached to the spacer. The thermally actuated spacer adjusts the cavity length by up to about 20 microns. A second feedback loop coupled to the sensor and heater provides a “coarse” control over the cavity length. An alternative embodiment provides a quasi-monolithic optical parametric oscillator (OPO). This embodiment includes a non-linear optical element within the resonator cavity along the optical path. Such an OPO configuration is broadly tunable and capable of mode-hop free operation for periods of 24 hours or more.

Mode structure and ray dynamics of a parabolic dome microcavity

Abstract: We consider the wave and ray dynamics of an electromagnetic field in a parabolic dome microcavity. The structure of the fundamental s wave involves a main lobe in which the electromagnetic field is confined around the focal point in an effective volume of the order of a cubic wavelength, while modes with finite angular momentum have a structure that avoids the focal area and have correspondingly larger effective volumes. The ray dynamics indicate that the fundamental s wave is robust with respect to small geometrical deformations of the cavity, while the higher order modes are unstable, giving rise to optical chaos. We discuss the incidence of these results on the modification of the spontaneous emission dynamics of an emitter placed in such a parabolic dome microcavity.

Modification of Spontaneous Emission of a Single Quantum Dot

Abstract: Modification of spontaneous emission of a single InAs quantum dot is demonstrated using an epitaxial distributed Bragg reflector microcavity that has been post-growth processed into microposts. The micropost structure isolates single quantum dots within the microcavity resonance, and creates a three-dimensionally (3D) confined photonic cavity. Discrete mode structure from the 3D cavity is observed, as well as the coupling of a single quantum dot to one of these modes in the weak coupling cavity QED regime.

Electronic energy transfer in a microcavity

Abstract: We study the microcavity effect on energy transfer via the electromagnetic field. The modification of the optical properties of the microcavity due to the presence of absorbing acceptors is taken into account. We analyze different cases that may be realized depending on the characteristics of the acceptor absorption band: the case of strong and broad absorption, when the cavity mode is practically destroyed; the regime of weak absorption, when the cavity mode is still well defined and just acquires some additional broadening; and the strong-coupling regime, when the acceptor absorption has the shape of a strong and narrow peak and two polariton branches appear, formed due to coherent mixing of the acceptor excitations and the cavity mode. In our calculations we use a realistic model for the cavity mirrors (dielectric or metallic), which is important since the mirrors introduce an additional decay channel for the donor excitation besides the transfer to the acceptors. The distribution of the energy between different decay channels is analyzed in detail.

Method, chip, device and system for effecting and monitoring nucleic acid accumulation

Abstract: A nucleic acid accumulation analyzing chip comprising an optical waveguide having a radiation input port and a radiation output port, the optical waveguide being formed with at least one optical microcavity along its optical path, at least one oligonucleotide being immobilized to the optical waveguide in the microcavity, such that when the at least one oligonucleotide is contacted with reaction reagents under conditions allowing a nucleic acid accumulation reaction to take place, accumulated nucleic acid is detectable by providing radiation at the radiation input port of the optical waveguide and monitoring radiation signal modulation at the radiation output port of the optical waveguide.

Er3+ in strong light-confining microcavity

Abstract: Er3+ ions produce a sharp line emission that has small absorption cross section, long radiative lifetime, and is independent of external perturbations. These optical properties of the Er3+ ions limit the pumping efficiency and tunability of the emission line. In this work we present a study in which Er3+ emission was modified by coupling an ensemble of Er3+ ions to a microcavity resonance. The optical response of an optical cavity that consists of an Er2O3 layer confined between Si/SiO2 distributed Bragg reflectors is studied. When the cavity is in resonance with the optical transition of the Er3+ ions, the resonances in the reflectivity spectra split. The results are explained by a standard semiclassical model of atom–photon coupling.

Ultra-short laser-produced optical microcavities and ionization fronts

Abstract: A class of nonlinear optical effects related to fast field ionization in an interference pattern is investigated by numerical simulations. Interference between counter-propagating ultra-short pulses slightly below the ionization threshold produces a layered distribution of free-electron density. In a dense dielectric target, this effect allows us to trap light between plasma layers creating a sort of optical microcavity. Other peculiar features include frequency upshift, pulse lengthening and self-generated relativistic ionization fronts.

Exciton polaritons in a cylindrical microcavity with an embedded quantum wire.

Abstract: Exciton-light coupling in cylindrical microcavities containing quantum wires has been treated by means of classical electrodynamics within the nonlocal dielectric response model. A typical anticrossing behavior of quasi-one-dimensional exciton-polariton modes has been obtained, as well as the weak-coupling--strong-coupling threshold. Effects of the nonradiative damping of the exciton resonance in the quantum wire on the optical response of the microcavity structure have been analyzed.

Microcavity discharge device

Abstract: A microcavity discharge device generates radiation with wavelengths in the range of from 11 to 14 nanometers. The device has a semiconductor plug, a dielectric layer, and an anode layer. A microcavity extends completely through the anode and dielectric layers and partially into the semiconductor plug. According to one aspect of the invention, a substrate layer has an aperture aligned with the microcavity. The microcavity is filled with a discharge gas under pressure which is excited by a combination of constant DC current and a pulsed current to produce radiation of the desired wavelength. The radiation is emitted through the base of the microcavity. A second embodiment has a metal layer which transmits radiation with wavelengths in the range of from 11 to 12 nanometers, and which excludes longer wavelengths from the emitted beam.

Design, implementation, and characterization of a 2D bidirectional free-space optical link

Abstract: A vertical-cavity surface-emitting laser (VCSEL) based free- space parallel optical interconnect is presented. The rigid optical link interconnects bi-directionally two PCBs over a distance of 3 inches. The 512 optical channels were grouped in 4 by 8 clusters on a 750-micrometers pitch, where each cluster is a 4 by 4 array of channels on a 125-micrometers pitch. Modules combining both microlenses and minilenses were used to propagate light from the VCSELs to the detectors. Details of the optical design and assembly process are presented.17© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Polymer-based microcavity with photoencoded quadratic nonlinearity.

Abstract: Functional electro-optic polymer thin films embedded in microcavity structures have been poled by an all-optical procedure based on the interference of multiphoton absorption processes. The photoinduced χ2 tensor was then further addressed at modal resonance for the fundamental wavelength, leading to significant enhancement of the second-harmonic-generation efficiency. An order-of-magnitude enhancement, which is due to electric field resonant conditions inside the microcavity, has been probed by an optical parametric oscillator, in comparison with a single-path thin-film configuration. This configuration opens new perspectives in the realm of nonlinear photonic device processing.

Optical eigenmodes of a cylindrical microcavity

Abstract: The optical mode structure of a cylindrical microcavity has been investigated using a transfer matrix approach. We derive exact algebraic equations from which the frequencies of the optical eigenmodes of the two polarizations can be obtained, as well as approximate explicit algebraic expressions for those frequencies.

Semiconductor optical device and method of manufacturing the same

Abstract: The semiconductor optical device is provided with an optical waveguide part and an optical amplification part respectively provided on the GaAs semiconductor substrate. The optical amplification part includes at least one semiconductor optical amplifier. The optical waveguide part includes optical elements including optical waveguides. The optical waveguides are optically connected to the semiconductor optical amplifier. The semiconductor optical amplifier is provided with an active layer including a GaxIn1−xNyAs1−y semiconductor, a first conductive type clad layer and a second conductive type clad layer respectively with the active layer between them. The optical waveguides are respectively provided with a core semiconductor layer including at least either of a GaInNAs semiconductor or a GaAs semiconductor, a first clad semiconductor layer and a second clad semiconductor layer respectively with the core semiconductor layer between them.

Visible light emission from Si/SiO2 multilayers in planar microcavities

Abstract: Bright quantum-confined photoluminescence (PL) at visible wavelengths can be obtained from ultrathin-layer Si/SiO2 superlattices. We demonstrate that with the use of an optical resonator the PL peak wavelength and bandwidth can be modified selectively. The strong enhancement and subsequent decrease in the PL intensity in these superlattices with decreasing Si layer thickness has been investigated theoretically. Calculations of the band structure of a Si quantum well separated by crystalline SiO2 barriers using a tight-binding method reveal that the confined conduction and valence bands along the [001] symmetry direction are essentially dispersionless, are strongly nested, and have a direct band-gap character. The enhanced band-edge density of states and the stronger electron–hole interaction across the low-dielectric barriers lead to a competition between several length scales and produce the PL intensity variation with well width observed.