Showing papers on "Optical microcavity published in 1996"

Optical filter including a sub-wavelength periodic structure and method of making

Abstract: An optical filter includes a dielectric layer formed within a resonant optical cavity, with the dielectric layer having formed therein a sub-wavelength periodic structure to define, at least in part, a wavelength for transmission of light through the resonant optical cavity. The sub-wavelength periodic structure can be formed either by removing material from the dielectric layer (e.g. by etching through an electron-beam defined mask), or by altering the composition of the layer (e.g. by ion implantation). Different portions of the dielectric layer can be patterned to form one or more optical interference filter elements having different light transmission wavelengths so that the optical filter can filter incident light according to wavelength and/or polarization. For some embodiments, the optical filter can include a detector element in optical alignment with each optical interference filter element to quantify or measure the filtered light for analysis thereof. The optical filter has applications to spectrometry, colorimetry, and chemical sensing.

Real-time detection of individual atoms falling through a high-finesse optical cavity.

Abstract: The enhanced coupling between atoms and photons inside a high-finesse optical cavity provides a novel basis for optical measurements that continuously monitor atomic degrees of freedom. We describe an experiment in which cavity quantum-electrodynamic effects are utilized for real-time detection of individual atoms falling through an optical cavity after being dropped from a magneto-optical trap. Our technique permits experiments that are triggered by the presence of a single optimally coupled atom within the cavity mode volume.

High intensity single-mode VCSELs

Abstract: A VCSEL 101 comprising an optical cavity having an optical loss and a loss-determining element 117 coupled to the optical cavity. The loss-determining element 117 progressively increases the optical loss of the optical cavity with increasing lateral distance from the optical axis 105. The optical cavity includes a first mirror region 111, a second mirror region 107, a plane light-generating region 125 sandwiched between the first mirror region 111 and the second mirror region 107, perpendicular to the optical axis 105, and an element 113 that defines the lateral extent of the optical cavity in the plane of the light-generating region 125. The first mirror region 111 and the second mirror region 107 are both conductive and have opposite conductivity modes.

Widely tunable spectrum translation and wavelength exchange by four-wave mixing in optical fibers

Abstract: Summary form only given. Wavelength conversion has been the subject of much research in recent years. Various methods have been studied with use of optical nonlinearities in either semiconductors or fibers. We introduce a novel technique based on four-wave mixing (FWM) in fibers, which has the potential for achieving unit conversion efficiency. It involves only spectrum translation, not inversion or phase conjugation. It is widely tunable and can, in principle, shift wavelengths by tens and even hundreds of nanometers. It can also perform a novel optical function, namely, complete exchange of optical power between two wavelengths.

Directional light output from photonic-wire microcavity semiconductor lasers

Abstract: We have obtained directional light output from a recently realized InGaAsP photonic-wire microcavity ring lasers. The output was achieved by fabricating a 0.45-/spl mu/m-wide U-shape waveguide next to a 10-/spl mu/m diameter microcavity ring laser. The laser has a threshold pump power of around 124 /spl mu/W when optically pumped at 514 nm. It is comparable to the former structure without output coupling. The output coupling efficiency can be controlled carefully by choosing the spacing between the laser cavity and the waveguide.

Strongly directed single mode emission from organic electroluminescent diode with a microcavity

Abstract: The strongly directed spontaneous emission along the optical axis of an organic electroluminescent (EL) diode with a typical emitting material, tris(8‐quinolinolato) aluminum, is realized with a planner microcavity structure. The structure of the microcavity EL diode is designed to have a resonance condition in which the total optical length is 3/2λ and the resonance wavelength λ is located at shorter wavelength side of a natural emission spectrum of a noncavity EL diode.

Spontaneous emission in a planar Fabry-Pérot microcavity.

Abstract: ~Received 19 September 1995! We study the spontaneous-emission of a single atom located between two parallel infinite plates where one of the plates is partially reflective and the plate separation is of the order of the wavelength of the atomic transition. We pay particular attention to the nature of the field modes in such a finite finesse cavity, including the full three-dimensional nature of the field. We then compute the decay rate of an excited atom placed inside such a cavity. The angular distributions of the spontaneous-emission and of the cavity field vacuum fluctuation variances are investigated. Finally, we examine the output field from an atom inside a finite finesse microcavity. We show that the radiation transmitted outside such microcavity forms a nondiffracting Bessel beam.

Low threshold microcavity light emitter

Abstract: Disclosed is a low threshold vertical cavity surface emitter having a low refraction index confining layer directly in the cavity spacer. This allows a ½ wavelength cavity spacer and a lateral size of as low as 2 μm. Also disclosed is a method of rapid temperature annealing to seal a III-V crystal and inhibit oxidative degradation.

Raman efficiency in a planar microcavity.

Abstract: We present a model for Raman efficiency in a planar microcavity. We calculate the modifications of excitation and emission induced by optical confinement in a $\frac{3\ensuremath{\lambda}}{2}$-thick GaAs/AlAs multiple quantum well grown on a semiconductor-distributed Bragg reflector. Such a structure constitutes a low-finesse asymmetric microcavity. Both excitation and emission are shown to depend strongly on photon frequency, leading to enhancements of up to a factor of 50 for a double resonance process. The cavity-induced Raman efficiency modifications are tested by folded-acoustic- and optical-phonon scattering experiments, finding quantitative accord with theory.

Emission dynamics of In0.2Ga0.8As/GaAs λ and 2λ microcavity lasers

Abstract: We study the emission dynamics of two In0.2Ga0.8As/GaAs microcavity lasers after femtosecond optical excitation at 20 K. The pulse widths and the peak delays of λ and a 2λ cavity are compared. Pulses as short as 3.3 ps (9.5 ps) and peak delays as short as 8.2 ps (16.5 ps) are obtained with the 2λ cavity (λ cavity). The pulse widths and peak delays are well described by a model based on a rate equation analysis for carrier and photon densities; in particular, the better high speed characteristics of the 2λ cavity compared to the λ cavity are well reproduced.

Coherent control of quantum-well excitons in a resonant semiconductor microcavity for high-speed all-optical switching

Abstract: Coherent control of excitons in quantum wells embedded in a resonant planar semiconductor microcavity versus in quantum wells without the cavity at high repetition rates is investigated theoretically to determine the practical constraints for application in high bit-rate optical switching. It is shown that /spl pi/-shifted pulse pairs are optimal to coherently populate and depopulate the QW on the 100-fs timescale. For the cavity-free case, the small optical nonlinearity will require devices incorporating /spl sim/100 quantum wells; the resonant enhancement of the confined mode for the case of the cavity leads to an effective increase in the optical nonlinearity and thus a reduction of the required number of quantum wells to /spl sim/10. In addition, switch architectures that avoid interferometers, and thus will have superior temperature and mechanical stability, based on the microcavity are proposed. We believe that although room-temperature operation of a 100-Gb/s switch based on this principle may be difficult, operation at liquid-nitrogen temperature should be feasible.

Exciton-polariton ladder in a semiconductor microcavity.

Abstract: We investigated the strongly coupled single cavity photon state and multiple discrete quantum-well exciton states in a semiconductor microcavity. The measured exciton-polariton dispersion curves feature multiple anticrossing. The theoretical simulation is in good agreement with the experimental result. \textcopyright{} 1996 The American Physical Society.

Ultrafast balanced-homodyne chronocyclic spectrometer

Abstract: We describe an optical detection system for simultaneous time- and frequency-resolved measurements: the Balanced-Homodyne Chronocyclic Spectrometer (chrono equals time; cyclic equals frequency). This system uses balanced, optical homodyne detection, with a wavelength- tunable, pulsed local-oscillator (LO) field to time resolve the spectrum of weak light pulses. The LO field defines the time and frequency window in which the signal field is sampled. The method time resolves the photon statistics as well as the mean intensity. Measurement examples are given for: (1) Temporal oscillations of laser pulses transmitted through a semiconductor quantum well in an optical microcavity and (2) The time-frequency profile of a linearly chirped ultrashort laser pulse.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Coupling between one-dimensional excitons and two-dimensional photons: Quantum wires in a microcavity.

Abstract: Maxwell equations are solved for the light incident on the microcavity with an embedded periodical grating of quantum wires, taking into account the nonlocal excitonic contributions to the dielectric polarization. The dispersion of exciton polaritons created due to the coupling of one-dimensional excitons and two-dimensional photon modes is obtained. The backscattering of light due to its resonant diffraction at the grating of quantum wires is found to result in the four-mode polaritonic spectrum, while numerically calculated spectra of light reflection, absorption, and diffraction scattering show from two to four resonant features. \textcopyright{} 1996 The American Physical Society.

Light emission from vertical-microcavity quantum dot laser structures

Abstract: A vertical microcavity laser structure with an active layer of Stranski-Krastanow quantum dots was fabricated for the first time. The microcavity consists of an InGaAs quantum dot layer grown by MOCVD, located between two AlAs/Al0.2Ga0.8As distributed Bragg-reflector mirrors. The length of the microcavity was 4λ(λ = 884 nm). The cavity effect was evidenced by the difference of the PL linewidths of samples with and without the cavity.

Recent advances in semiconductor vertical cavity lasers for optical communications and optical interconnects

Abstract: We discuss error free optical fiber transmission at data rates up to 10 Gbit/s using high performance InGaAs strained QW vertical cavity surface emitting laser diode (VCSEL) sources. Fabricated multi-mode VCSELs achieve 50 mW maximum output power and 47% conversion efficiency. Single-mode devices have 290 /spl mu/A threshold current, 2.7 mW maximum output power, 27% conversion efficiency and 50 dB sidemode suppression.

Fabrication and low threshold current density CW operation of GaInAsP/InP multiple-reflector microcavity laser

Abstract: We report CW operation of a GaInAsP/InP multiple-reflector microcavity (MRMC) laser operated at fairly low threshold current density. The threshold current density with broad contact (stripe widthW=240 μm, cavity lengthL=60 μm) under pulsed operation was 180 A cm−2 (lth=20 mA), and was 230 A cm−2 under CW operation at room temperature operating at 1.52 μm wavelength.

Dynamics of four-wave mixing on excitons in a quantum optical microcavity

Abstract: A theory of degenerate four-wave mixing in a semiconductor optical cavity with quantum wells is constructed. The nonlinear response of a microcavity can be four to five orders of magnitude stronger than that of an isolated quantum well. For P2E-and P3-type nonlinearities the damped diffracted signal oscillates with a period determined by the Rabi splitting. For a biexcitonic mechanism of nonlinearity, the signal contains damped overtones of the Rabi splitting and the biexciton binding energy.

Magnetic and Electric Field Effects in Semiconductor Quantum Microcavity Structures

Abstract: The effects of magnetic and electric field on the vacuum Rabi exciton-photon coupling in semiconductor quantum microcavity structures are presented. A number of phenomena are described including marked increase (decrease) of the vacuum Rabi coupling in external magnetic (electric) field due to the increased (decreased) exciton oscillator strength, exciton Zeeman splitting, and unusual linewidth narrowing effects attributed to motional narrowing.

Enhancement of the Spontaneous Emission Rates in all Porous Silicon Optical Microcavities

Abstract: The emission properties of a porous silicon layer placed in an optical microcavity is investigated by photoluminescence and time resolved photoluminescence measurements. The microcavity is formed by an all porous silicon Fabry-Perot filter made by two distributed Bragg reflectors separated by a λ or λ/2 porous silicon layer. Our main findings are that the spontaneous emission spectrum is drastically modified: the linewidth is narrowed, the time decay of the emission is shortened by a factor of about 2/3 at room temperature and the peak emission intensity is increased by a factor of more than 10. These facts are caused by the redistribution of the optical modes in the microcavity due to the presence of the optical resonator and to the variation of the dielectric environment.

Photonic microstructures for the next generation of microcavity lasers

Abstract: Summary form only given. We present the first experimental demonstration of a two-dimensional photonic bandgap (2D PBG) at optical wavelengths and the localisation of light at a defect in a lD PBG structure. These are major milestones for a novel class of waveguide based GaAs-AlGaAs microcavity semiconductor lasers with very low threshold, reduced noise and a substantial degree of spontaneous emission control.