Showing papers on "Optical microcavity published in 1997"

Optical electronics in modern communications

Abstract: 1. Electromagnetic Theory 2. The Propagation of Rays and Beams 3. Propagation of Optical Beams in Fibers 4. Optical Resonators 5. Interaction of Radiation and Atomic Systems 6. Theory of Laser Oscillation and its Control in the Continuous and Pulsed Regimes 7. Some Specific Laser Systems 8. Second-Harmonic Generation and Parametric oscillation 9. Electronic Modulation of Laser Beams 10. Noise in Optical Detection and Generation 11. Detection of Optical Radiation 12. Interaction of Light and Sound 13. Propagation of Coupling Modes in Optical Dielectric Waveguides-Periodic Waveguides 14. Holography and Optical Data Storage 15. Semiconductor Lasers-Theory and Applications 16. Advanced Semiconductor Lasers: Quantum Well Lasers, Distributed Feedback Lasers, Vertical Cavity Surface Emitting Lasers 17. Phase Conjugate Optics - Theory and Applications 18. Two-Beam Coupling and Phase Conjugation in Photorefractive Media 19. Optical Solitons 20. A Classical Treatment of Quantum Optics Appendices A. The Kramers-Kroning relations B. The Electrooptic Effect in Cubic 43m Crystals C. Noise in Traveling Wave Lasers Amplifiers D. Transformation of a coherent

Experimental study of integrated-optics microcavity resonators: Toward an all-optical switching device

Abstract: An integrated all-optical switch based on a high-Q nonlinear cylindrical microcavity resonator is proposed. The switch consists of single mode planar waveguides that allow coupling light in and out to a microresonator, exhibiting whispering gallery modes. Due to the high Q factor and the small dimensions, fast switching at low power is feasible for devices based on presently available nonlinear polymers as the active material. In this approach, the transmission of an integrated optical waveguide close to a microcavity has been measured and related to the resonances of the cylindrical microcavity.

Microcavity effects in gan epitaxial films and in ag/gan/sapphire structures

Abstract: Luminescence spectra of GaN epitaxial layers grown on sapphire display a strong intensity modulation of the below-band gap transitions and on the low-energy side of the near-band gap transition. The intensity modulation is attributed to a microcavity formed by the semiconductor–air and semiconductor–substrate interface. The microcavity effect is enhanced by using metallic reflectors which increase the cavity finesse. It is shown that microcavity effects can be used to determine the refractive index of the microcavity active material. Using this method, the GaN refractive index is determined and expressed analytically by a Sellmeir fit.

Size Dependence of Confined Optical Modes in Photonic Quantum Dots

Abstract: Confined optical modes in semiconductor microcavities with lateral sizes between 5 and 1 \ensuremath{\mu}m have been investigated by optical spectroscopy. In the laterally patterned structures the optical mode spectrum of the vertical cavity splits into several lines. With decreasing lateral size the modes shift to higher energies, and the splitting between the modes increases. The observed dot size variation of the optical eigenmodes is in quantitative agreement with numerical calculations of quantized photon states in these three-dimensional optical cavities.

Organic electroluminescent device with plural microcavities

Abstract: An OED with a first microcavity including a first transparent spacer positioned adjacent the diode light output and a first mirror stack positioned on the first spacer to reflect light back into the OED and to define an optical length of the first microcavity. The optical length of the first microcavity being such that light emitted from the first microcavity has a first spectrum. A second microcavity including a second transparent spacer positioned adjacent the first microcavity and a second mirror stack positioned on the second spacer to reflect light toward the first microcavity and to define an optical length of the second microcavity. The optical length of the second microcavity being such that light emitted from the second microcavity has a second spectrum. Additional microcavities can be placed in the structure to further enhance and alter the light spectrum.

Dynamics Of Dual-wavelength Emission From A Coupled Semiconductor Microcavity Laser

Abstract: We present an experimental demonstration of the dynamics of dual-wavelength emission from a coupled semiconductor microcavity laser after femtosecond optical excitation at 20 K. The coupled microcavity laser is comprised of two λ sized Al0.2Ga0.8As/Al0.5Ga0.5As cavities, separated by a common mirror. The bottom cavity contains three 10 nm thick GaAs quantum wells (QWs) whereas the top cavity contains three 16 nm thick GaAs QWs. Time-resolved measurements of the stimulated emission show pulses as short as 4.8 ps (10 ps) and peak delays as short as 13 ps (16 ps) for the shorter (longer) emission wavelength. Fast pulse fall times of 1 ps are observed for the pulses of the shorter emission wavelength which can be explained by the simultaneous interaction of the two photon modes with both gain regions of the two types of QWs.

Optical near-field response of semiconductor quantum dots

Abstract: The near-field response of optically excited semiconductor quantum dots is theoretically investigated for the collection and illumination mode of a scanning near-field optical microscope. The study includes resolution, spectral line shape, and field distributions of single and interacting dots. It is shown that in contrast to near-field excitation of molecules with large dipole moments, the line shape and position of typical semiconductor quantum dots can be determined without a disturbance if realistic values for the intrinsic linewidth are assumed. The comparison of regular and irregular quantum-dot distributions yields characteristic signatures for disordered arrays, necessary to understand the optical response of realistic semiconductor quantum dot samples.

Excitation of a single molecule on the surface of a spherical microcavity

Abstract: We use the optical resonance of a spherical microcavity (quality factor ∼106) to excite a single molecule. By attaching a p-terphenyl crystal doped with pentacene and terrylene molecules to a dielectric sphere, we detect individual molecules excited by the near field of the cavity. A low-temperature optical microscope is utilized to image the emission from the single molecule, determine its position on the sphere surface, and measure its absorption linewidth. These results demonstrate the feasibility of single-molecule cavity quantum electrodynamics.

Wavelength compensation for resonant cavity electroluminescent devices

Abstract: Disclosed is a microcavity organic light emitter having reduced variation in emission spectra per change in viewing angle. In an illustrative embodiment, a microcavity EL device comprises a microcavity layer structure stacked on a symmetric, non-planar surface of a substrate. The microcavity layer structure includes at least a first reflective layer on the non-planar substrate surface, a second reflective layer and an active layer having organic material capable of electroluminescence between the first and second reflective layers. The non-planar surface may be a shallow cone, frustum, a dome-like surface, or a combination thereof.

Transition from a microcavity exciton polariton to a photon laser

Abstract: In a previous paper [Phys. Rev. A 54, R1789 (1996)], we reported the observation of a laserlike transition in a single GaAs quantum well microcavity and gave the interpretation as spontaneous buildup of coherent exciton-polariton population via stimulated polariton-phonon emission. In this Brief Report, we present new experimental data and correct our previous interpretation for the microcavity polariton system at high density. We observe a continuous transition from a microcavity polariton emission to a bare photon laser. This conclusion is based on the measurements of the angular resolved photoluminescence, linewidth, and intensity of the lasing line as well as the reflection spectrum under cw pumping.

Eigenmode confinement in the dielectrically apertured Fabry-Perot microcavity [VCSEL]

Abstract: The three-dimensional (3-D) optical confinement of the dielectrically apertured Fabry-Perot microcavity is analyzed by considering electromagnetic coupling between the confined region and parasitic waveguide modes that exist outside the aperture. If the cavity length is close to one-half the emission wavelength and for large enough aperture sizes, all parasitic waveguide modes can be evanescent except one which couples only weakly to the emitting region. If the aperture diameter is too small, loss of optical confinement is predicted, and the optical mode size at which this occurs can be estimated from the cavity length and the relative shifts in the vertical resonances inside and outside the apertured region.

Output control of vertical microcavity light emitting device

Abstract: An improved intracavity sensor based output power control for microcavity light emitting devices. An improved phototransistor transducer is both configured and physically disposed so that it passively transmits the spurious optical energy output of the microcavity light emitting device while simultaneously generating a light determined electrical signal of easily used large magnitude that is nearly free of error. The base-collector region of the transistor is disposed with a quantum well absorbing layer and produces a signal responsive to a selected emission wavelength. The configuration of the optical energy communicating transducer is arranged so that it is improved in sensitivity and especially in selectivity in generating the laser feedback signal.

Time-resolved photoluminescence of all-porous-silicon microcavities

Abstract: The emission property 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 $\ensuremath{\lambda}$ or $\ensuremath{\lambda}$/2 porous silicon layer. The 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 cavity due to the presence of the optical resonator and to the variations in the dielectric environment where the radiative emission takes place.

Vertical Microcavity Lasers with InGaAs/GaAs Quantum Dots Formed by Spinodal Phase Separation.

Abstract: We report the growth, characterization and lasing of vertical microcavity lasers with an active layer of self-organized InGaAs/GaAs quantum dots. The quantum dots are formed by spinodal phase separation in low-In-content (x=0.03) Inx Ga1-x As epilayers deposited with decreasing growth temperature in a hot-wall metalorganic chemical vapor deposition reactor. Optical transitions involving ground and excited states of the quantum dots were investigated using photoluminescence at moderately high excitation densities. Lasing oscillation was observed at 77 K by optical pumping. The coupling parameter β of the spontaneous emission into the lasing mode was estimated to be ~8×10-3.

Quantum well exciton-polariton light emitting diode

Abstract: A light emitting device made of semiconducting materials. The device has an optical microcavity which supports a resonant mode of predetermined photon energy. Within the cavity is a quantum well of predetermined thickness and energy depth. The quantum well is designed such that it forms bound electron, exciton, lower polariton, and hole energy states of predetermined energy. The energy of an exciton state is set to equal the predetermined photon energy of the microcavity mode such that polariton states are created. A means is provided for resonantly tunneling electrons into a quantum well energy state. In a first embodiment, electrons resonantly tunnel into an electron energy state. In a second embodiment, electrons resonantly tunnel into an exciton energy state, during which tunneling the electrons simultaneously fuse with holes to form excitons. In the first embodiment, the electron state to lower polariton state transition energy is made equal to the energy of a longitudinal optical (LO) phonon of the quantum well material. This energy equivalence facilitates the rapid thermalization of resonantly tunneled electrons to combine with holes and form polaritons resonant with the cavity mode. Thermalization is rapid because it only requires the scattering of a single LO phonon. The photon component of the polariton is then emitted through the leaky cavity reflector. The second embodiment sets the exciton to polariton transition energy equal to the LO phonon energy to facilitate rapid thermalization to the polariton state. Photons are then emitted through the leaky Bragg reflector in the same manner as the first embodiment.

Laser emission from photonic dots

Abstract: Laser emission was observed in photonic semiconductor dots with a discretized optical mode spectrum. The photonic dots with lateral sizes between 1 and 5 μm provide a three-dimensional optical confinement by using in the vertical direction AlAs/GaAs Bragg mirrors and in the lateral directions the refractive index discontinuity at the etched surfaces. In the optically pumped structures, the laser emission takes place on the fundamental mode of the microcavities. External threshold excitation densities of 200 W/cm2, which correspond to a very low internal optical excitation power of 0.15 μW per microcavity post, were measured for microcavity structures with a lateral size of 2.7 μm.

Mapping the confined optical field in a microcavity via the emission from a conjugated polymer

Abstract: The distribution of a confined optical field within a microcavity was determined using a thin layer of the fluorescent polymer PPV as a probe of the local-field amplitude. It is shown that the photoluminescence emission intensity from the cavity is a function of the axial position of the polymer, and confirms that a microcavity can be used to control spontaneous emission.

Optical semiconductor device and method of fabricating the same

Abstract: There is provided an optical semiconductor device including an optical waveguide structure having a quantum well layer and an optical confinement layer as a core layer, wherein the core layer has a thickness varying in a lengthwise direction of the optical waveguide to thereby have a function of spot-size conversion, and the quantum well layer is designed to have a band-gap energy which is constant within ±30 meV in the direction. The above-mentioned optical semiconductor device makes it possible to an optical gain to laser oscillation wavelength over all ranges of a resonator, and hence makes it no longer necessary to form a region only for spot-size conversion (SSC). This ensures that a device length can be as small as that of a conventional laser diode. In addition, lower threshold value characteristic and high temperature operation performance could be achieved, and a yield in devices per a wafer can be significantly enhanced.

High brightness single mode vcsel

Abstract: PROBLEM TO BE SOLVED: To obtain a vertical resonance surface emission laser emitting a high intensity single mode light beam along the optical axis by providing a loss determination element coupled with an optical cavity and increasing the optical loss in the optical cavity gradually as the sideways distance from the optical axis increases. SOLUTION: A VCSEL(vertical resonance type surface emission laser) 101 comprises a loss determination element 117 coupled with an optical cavity 103. The loss determination element 117 increases the optical loss in the optical cavity 103 gradually as the distance from the optical axis 105 increases sideways γ. When the optical loss in the optical cavity 103 increases at a position remote sideways from the optical axis 105 during a single mode operation of the VCSEL 101, a threshold value of carrier density required for starting multimode operation increases significantly. Since the loss determination element 117 at least delays starting of multimode operation in VCSEL 101, maximum intensity of a single mode light to be generated from the VCSEL 101 is increased significantly.

Ultrafast study of spontaneous emission from conjugated polymer microcavities

Abstract: Results are presented of femtosecond photoluminescence spectroscopy and photoluminescence quantum efficiency measurements of a planar conjugated polymer microcavity consisting of a layer of poly(p-phenylenevinylene) sandwiched between a dielectric mirror and an evaporated metallic layer. By comparison with measurements of a similar structure in the absence of the metallic mirror it is shown that the spontaneous emission rate is not increased notably due to the optical confinement of the microcavity, even though the emission is significantly enhanced in the forward direction. The time-resolved photoluminescence spectra highlight the rapid vibrational relaxation and energy migration of excitons that occur in conjugated polymers.

Angular distribution of the spontaneous emission in a planar dielectric dye microcavity

Abstract: The angular distribution of the radiation emitted from a dye molecular solution in a planar symmetrical microcavity terminated by two high-reflectivity dielectric mirrors has been investigated. A quantum-mechanical analysis of this process was applied to a microcavity terminated by mirrors bearing dielectric multilayered coatings, whose optical parameters are calculated by means of the Lissberger–Wilcock algorithm. The experiment was performed for different polarizations of the pump beam and of the emitted radiation. The angular distribution of the spontaneous emission is strictly dependent on the behavior of the reflectivity and the phase of the mirrors relative to the angle of incidence. This restriction limits the microcavity confinement to relatively small values of the internal angle of emission.

Interference scanning optical probe microscopy

Abstract: We describe an optical scanning probe technique (Interference Scanning Optical Probe Microscopy) with enhanced resolution possibilities not limited by the aperture size of the optical probe. This is realized using a substrate in the form of a microcavity and probe collection mode in reflection geometry. The microcavity consisting of an opaque and a transparent layer, is used to shift the phase of the wave scattered from the adsorbate with respect to the incident and reflected beams. Using this technique silver island films have been detected with resolution better than 40 nm with a nominal probe aperture size of 100 nm.

Influence of carrier relaxation on the dynamics of stimulated emission in microcavity lasers

Abstract: The influence of carrier relaxation on the emission dynamics of a semiconductor microcavity laser is investigated using femtosecond optical excitation. For moderate excitation intensities, the dynamics of the output laser pulse becomes significantly slower when the photon energy of the pump laser is tuned from the quantum well band-gap energy towards higher energies. Theoretical calculations reproduce this trend only if the interaction-induced dephasing of the polarization driven by the pump pulse, the formation, and relaxation of the nonequilibrium carrier distribution as well as the chirp of the excitation pulse are taken into account. Additionally, band-structure effects such as excitation of light holes influence the thermalization dynamics and lead to discontinuities in the general trend.

Quantum optical semiconductor device producing output optical emission with sharply defined spectrum

Abstract: An optical semiconductor device includes a plurality of quantum structures in an active layer thereof, wherein each of the quantum structures is confined in at least two of the three, mutually perpendicular dimensions, and wherein at least two of the quantum structures are separated with a distance that allows tunneling of carriers therebetween.