Showing papers on "Optical microcavity published in 2001"

Design of photonic crystal microcavities for cavity QED

Abstract: We discuss the optimization of optical microcavity designs based on two-dimensional photonic crystals for the purpose of strong coupling between the cavity field and a single neutral atom trapped within a hole. We present numerical predictions for the quality factors and mode volumes of localized defect modes as a function of geometric parameters, and discuss some experimental challenges related to the coupling of a defect cavity to gas-phase atoms.

Single-mode spontaneous emission from a single quantum dot in a three-dimensional microcavity.

Abstract: The spontaneous emission from an isolated semiconductor quantum dot state has been coupled with high efficiency to a single, polarization-degenerate cavity mode. The InAs quantum dot is epitaxially formed and embedded in a planar epitaxial microcavity, which is processed into a post of submicron diameter. The single quantum dot spontaneous emission lifetime is reduced from the noncavity value of 1.3 ns to 280 ps, resulting in a single-mode spontaneous emission coupling efficiency of 78%.

Optical heterodyne detection in optical cavity ringdown spectroscopy

Abstract: The present invention relates to optical heterodyne detection cavity ringdown spectroscopy. In one aspect the invention relates to an optical system (1) comprising a ringdown cavity cell (3) defining a resonant optical cavity, means for directing coherent light selected from the group consisting of continuous or quasi-continuous light into said optical cavity (8, 9, 10, 11 and 12), means for altering the resonant optical cavity so as to generate a frequency shift of the coherent light in the optical cavity (6, 7), means for coupling said coherent light into the optical cavity and means for decoupling the frequency shifted coherent light out of said optical cavity (5, 6, 7), means for optically combining (10, 11, 12) said decoupled frequency shifted coherent light with another portion of coherent light not in optical communication with the optical cavity and means for optical heterodyne detection (13) of the intensity of said combined light. A method for optical detection is also described as well as methods and apparatus for detecting a parameter of a sample.

Characteristics of a photonic bandgap single defect microcavity electroluminescent device

Abstract: A microcavity surface-emitting coherent electroluminescent device operating at room temperature under pulsed current injection is described. The microcavity is formed by a single defect in the center of a 2-D photonic crystal consisting of a GaAs-based heterostructure. The gain region consists of two 70-/spl Aring/ compressively strained In/sub 0.15/Ga/sub 0.85/As quantum wells, which exhibit a spontaneous emission peak at 940 nm. The maximum measured output power from a single device is 14.4 /spl mu/W. The near-field image of the output resembles the calculated TE mode distribution in a single defect microcavity. The measured far-field pattern indicates the predicted directionality of a microcavity light source. The light-current characteristics of the device exhibit a gradual turn-on, or a soft threshold, typical of single- or few-mode microcavity devices. Analysis of the characteristics with the carrier and photon rate equations yields a spontaneous emission factor /spl beta//spl ap/0.06.

Optical microcavity resonator sensor

Abstract: An optical resonator accelerometer (10) includes an optical microcavity (30) and an optical waveguide (20) that evanescently couples light incident on an input end of the waveguide core into the high-Q WGMs of the microcavity (30) at a coupling efficiency of over 99%. The waveguide (20) includes a waveguide core (340), and a multi-layer dielectric stack (330) that has alternating high an low refractive index dielectric layers (331, 332). The reflectivity of the dielectric stack is sufficient to isolate the waveguide core and the microcavity from the substrate (320). A flexure (40) has a first end mounted to the substrate, and a second end arranged to interact with said optical microcavity. The flexure is responsive to an inertial input to cause a change in the coupling geometry between the microcavity and the optical waveguide.

Optical sensor for measuring physical and material properties

Abstract: An optical medium having a cavity that defines a variable gap is provided. The optical medium is used in an optical sensor, laser, and variable frequency resonator, by way of example. The cavity is physically altered in response to changes in a measurable parameter like pressure, temperature, force, flow rate, and material composition. The optical medium is characterized in some embodiments by having a cavity disposed near or within a high Q optical resonator. The optical resonator can be formed by various structures of which Bragg reflector cavities, ring resonators, microdiscs, and microspheres are examples. The optical resonator is preferably coupled to a laser source. The altering of the cavity affects the resonance condition within the optical resonator and thereby the laser signal of the system. If the laser source is a mode locked laser, the repetition rate of the pulse train changes in response to changes in the measurable parameter. If the laser source is a CW source the frequency of the laser signal is dependent upon a measurable parameter.

Coupled optical microcavities in one-dimensional photonic bandgap structures : Special issue on photonic bandgaps

Abstract: We present a detailed theoretical and experimental study of the evanescent coupled optical microcavity modes in one-dimensional photonic bandgap structures. The coupled-cavity samples are fabricated by depositing alternating hydrogenated amorphous silicon nitride and silicon oxide layers. Splitting of the eigenmodes and formation of a defect band due to interaction between the neighbouring localized cavity modes are experimentally observed. Corresponding field patterns and the transmission spectra are obtained by using transfer matrix method (TMM) simulations. A theoretical model based on the classical wave analogue of the tight-binding (TB) picture is developed and applied to these structures. Experimental results are in good agreement with the predictions of the TB approximation and the TMM simulations.

Coupled optical microcavities in one-dimensional photonic bandgap structures

Abstract: We present a detailed theoretical and experimental study of the evanescent coupled optical microcavity modes in one-dimensional photonic bandgap structures. The coupled-cavity samples are fabricated by depositing alternating hydrogenated amorphous silicon nitride and silicon oxide layers. Splitting of the eigenmodes and formation of a defect band due to interaction between the neighbouring localized cavity modes are experimentally observed. Corresponding field patterns and the transmission spectra are obtained by using transfer matrix method (TMM)simulations. A theoretical model based on the classical wave analogue of the tight-binding (TB)picture is developed and applied to these structures. Experimental results are in good agreement with the predictions of the TB approximation and the TMM simulations.

Coated optical microcavity resonator chemical sensor

Abstract: A miniaturized chemical sensor features an optical microcavity (12) coated with a surface layer (14), and a waveguide (18) that evanescently couples light into the microcavity (12) The surface layer (14) is adapted to chemically interact with one or more molecule species in a chemical vapor surrounding the microcavity (12), so as to alter the evanescent light The chemical interaction causes a change in the index of refraction of the microcavity (12), resulting in a measurable phase different readout The refractive index sensitivity is substantially increased because of the high Q-value of the optical microcavity (12)

Direct measurement of the quality factor in a two-dimensional photonic-crystal microcavity.

Abstract: A new microcavity design is proposed and structures are realized with a two-dimensional photonic-crystal slab. The cavity consists of seven defect holes that encompass a hexagon and is designed to reduce vertical light leakage. From a direct transmission measurement, a Q value of 816+/-30 is achieved at lambda =1.55 mum . This high- Q cavity will permit the realistic realization of spontaneous-emission modification and on-off optical switches.

Silicon nanocrystals and Er3+ ions in an optical microcavity

Abstract: The characteristics of Si nanocrystals (nc) and Er-doped Si nc embedded within Si/SiO2 Fabry–Perot microcavities are investigated It is shown that very narrow (Δλ∼15 nm) and intense luminescence peaks can be obtained within the 600–1000 nm wavelength range for Si nc and at around 154 μm for Er-doped Si nc by properly varying the cavity resonance The luminescence intensity of the on-axis emission is over an order of magnitude above that of similar samples without a cavity and the overall luminescence is confined within a 30° cone from the sample normal The properties of these cavities are presented and the implications of the results discussed

Tailoring of the resonant mode properties of optical nanocavities in two-dimensional photonic crystal slab waveguides : Special issue on photonic bandgaps

Abstract: Optically thin dielectric slabs, in which a fully etched-through two-dimensional patterning is applied, are used to form high-Q optical cavities with modal volumes approaching the theoretical limit of a cubic half-wavelength. Resonant cavities are formed from local defect regions within the photonic lattice. Simple group theoretical techniques are developed to design cavities which support resonant modes with a particular polarization and radiation pattern. Numerical simulations using the finite-difference time-domain method are then used to study the detailed emission and loss properties of these modes. The cavities are probed spectroscopically through photoluminescence measurements, which when compared with numerical results show the presence of both donor and acceptor type modes. These experimental results show the predictive power of the modest symmetry analysis presented here in describing highly localized defect states within photonic crystals.

Optical response of a quantum dot superlattice under electric and magnetic fields

Abstract: We report calculations of the optical absorption of excitonic states in a linear array of quantum dots in the presence of electric and magnetic fields aligned with the array axis. In this system, in addition to the quantum dot geometric confinement and the Stark confinement, it is also present the confinement induced by the magnetic field that modifies the lateral characteristic energies of the system. The competing action between the effects of the electron-hole correlation and the different mechanisms of quantum confinement produces a rich structure in the spectrum. We show results for a large range of external field values and for different geometric confinement regimes.

Resonant microcavity display with a light distribution element

Abstract: A resonant microcavity display (20) having microcavity with a substrate (25), a phosphor active region (50) and front and rear reflectors (30 and 60). The front and rear reflectors may be spaced to create either a standing or treaveling eledtromagnetic wave to enhance the efificenty of the light transmission.

Optical integrated circuit substrate and optical module

Abstract: An object of the invention is to provide an optical integrated circuit substrate capable of establishing optical connection between an optical waveguide and a semiconductor light-receiving element with high light-receiving efficiency and of achieving low-loss light transmission. In the optical integrated circuit substrate, on a substrate is formed an optical waveguide having a clad and a core layer. Embedded in the optical waveguide are a metal placement portion for an optical element and a thin-film optical element placed thereon. Distance between the thin-film optical element and the core layer is reduced. In a region free of the thin-film optical element, there is an adequate distance between the core layer and the substrate. This allows satisfactory optical connection between the thin-film optical element and the optical waveguide. In the thin-film optical element-free region, low-loss light transmission is achieved without interaction between transmitted light and the substrate.

Strong enhancement of spontaneous emission in amorphous-silicon-nitride photonic crystal based coupled-microcavity structures

Abstract: We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry–Perot (FP) resonator and a coupled-microcavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation.

Giant optical responses in microcavity-fractal composites

Abstract: Optical properties of fractal nanostructured composite materials are considered. The fractal geometry results in localization of plasmon excitations in the hot spots, where the local field can exceed the applied field by several orders of magnitude. The high local fields of the localized fractal modes result in dramatic enhancement of optical responses, making feasible the surface-enhanced nonlinear spectroscopy of single molecules and nanocrystals. The field enhancement becomes especially large when fractals are placed inside a microcavity. A theory for the enhanced Raman and hyper-Raman surface-enhanced scattering in microcavity-fractal composites is developed.

Evanescent-wave coupled microcavity laser

Abstract: Disclosed is an evanescent-wave-coupled microcavity laser in which a gain medium is positioned outside a circularly symmetric microcavity having a size of a few tens of microns to a few hundreds of microns to generate a laser oscillation using a gain medium existing in the evanescent-field of a resonance mode. Particularly, a gain medium containing a semiconductor, atoms, molecules, or quantum dots is placed outside the microcavity where the evanescent-wave of the microcavity mode exists, to be excited by an electric or an optical pumping. Fluorescence irradiated from the excited gain medium is coupled with the evanescent-wave of the resonator mode to obtain a gain, so that amplification of light is triggered. The amplified light circulates inside the microcavity through total internal reflection to induce a stimulated emission of radiation from the excited gain medium in the field of evanescent-wave so that a stable laser oscillation is established. Particularly, the present invention includes the evanescent-wave-coupled microcavity lasers using the microspheres of extremely low energy loss, microdisks or microcylinders capable of being large-scale integrated.

Photoluminescence study of CdSexS1-x quantum dots in a glass spherical microcavity

Abstract: The photoluminescence (PL) of CdSexS1-x semiconductor quantum dots (QDs) in a glass spherical microcavity is investigated. The CdSexS1-x semiconductor clusters embedded in a glass matrix are fabricated by using the heat treatment method. Periodical structures consisting of sharp spectral lines are observed in the PL spectra of CdSexS1-x QDs, which can be well explained by the coupling with the whispering gallery modes of the spherical microcavity based on Mie scattering theory.

Microcavity-based optical channel router

Abstract: An optical channel add/drop router includes at least one optical waveguide disposed on a substrate, and an optical microcavity resonator. Each waveguide includes a waveguide core, and a multi-layer dielectric stack with alternating high and low refractive index dielectric layers. Light propagates from one of the I/O ports or add/drop port of the waveguide, through one of the waveguide channels. Frequency components of the light that match a resonant mode of the microcavity are coupled into the microcavity, and out of the microcavity onto a different waveguide channel, so that desired channels are added to or dropped from the input signal. Optical power transfer efficiency of over 95% can been achieved at a transfer linewidth of about 1 MHz.

Experimental analysis of the whispering-gallery modes in a cylindrical optical microcavity

Abstract: A real-space study of a cylindrical integrated optical microcavity by means of a photon scanning-tunneling microscope with a resolution of 50 nm reveals optical intensity distributions in great detail. Moreover, novel phenomena such as polarization conversion and conversion from copropagation to counterpropagation are observed. We present detailed maps of the optical field distribution of the whispering-gallery modes inside the microcavity as a function of both wavelength and position. We have made a quantitative comparison between measured and calculated field distributions. As a result, the buildup of the various whispering-gallery modes is better understood.

Multi-channel DWDM transmitter based on a vertical cavity surface emitting laser

Abstract: A multi-channel light source for use with a wavelength division multiplexed optical communication system includes a modified vertical cavity surface emitting laser (VCSEL) including a gain region and a resonator reflector layer at a first end for coupling with an optical fiber. An optical or electrical pumping source excites a gain region of the laser. An external cavity couples at a second end of the modified VCSEL and has a mirrored end for forming a resonant cavity with the resonator reflector layer permitting the light source to produce a multi-channel optical signal. The modified VCSEL has a cavity length that is substantially extended compared with a conventional VCSEL.

Correlation effects in the excitonic optical properties of semiconductors

Abstract: A microscopic many-body theory for the optical and electronic properties of semiconductors is reviewed with an emphasis on the role of correlation effects. At the semiclassical level, the semiconductor Bloch equations include many-body effects via bandgap and field renormalization as well as correlation contributions representing two electron-hole pair amplitudes, excitonic populations, and coupled interband and intraband coherences. These Coulomb interaction induced carrier correlations lead to characteristic signatures in nonlinear semiconductor spectroscopy. At the fully quantum mechanical level the dominant light-matter correlations are described by coupled semiconductor Bloch and luminescence equations. Excitonic emission properties of quantum well and microcavity systems are discussed, including effects such as coherent signatures in the secondary emission and coherent control of the emitted light.

Quantum semiconductor device having quantum dots and optical detectors using the same

Abstract: An optical detector includes a pyramidal etch-pit formed in a layered semiconductor structure. A channel layer is provided on facets of the pyramidal etch-pit and a hole-accumulation layer, sandwiched by a pair of barrier layers is formed on the channel layer. Further, electrodes are provided on a top surface and a bottom surface of the layered semiconductor structure. An optical window is provided so as to introduce an optical beam to the channel layer or the hole-accumulation layer.

Micro-optic absorption spectrometer

Abstract: An infrared absorption spectrometer (10) features an optical microcavity (12), and a waveguide (18) that evanescently couples light into the microcavity (12). The optical resonance frequency of the microcavity (12) is tuned to coincide with an atomic or molecular resonance frequency of a selected atom or molecule. In this way, light coupled into the microcavity (12) will experience absorption in the presence of an atomic or molecular substance. The absorption causes a measurable change in the evanescent light coupling into the microcavity (12). The detection sensitivity of the spectrometer (10) is significantly increased, compared to prior art spectrometers, because of the high Q value of the microcavity (12) and the ensuing long optical path lengths of the resonant modes traveling within the microcavity (12).