Showing papers on "Spontaneous emission published in 2003"
Journal Article•
TL;DR: Optical microcavities confine light to small volumes by resonant recirculation as discussed by the authors, and are indispensable for a wide range of applications and studies, such as long-distance transmission of data over optical fibres; they also ensure narrow spot-size laser read/write beams in CD and DVD players.
Abstract: Optical microcavities confine light to small volumes by resonant recirculation. Devices trased on optical microcavities are already indispensable for a wide range of applications and studies, For example, microcavities made of active III-V semiconductor materials control laser emission spectra to enable long-distance transmission of data over optical fibres; they also ensure narrow spot-size laser read/write beams in CD and DVD players. In quantum optical devices, mocrocavities can coax atoms or quantum dots to emit spontaneous photons In a desired direction or can provide an environment where dissipative mechanhms such as spontaneous emission are overcome so that quantum entanglement of radiation and matter is possible. Applications of these remarkable devices are as diverse as their geometrical and resonant properties.
1,855 citations
IBM1
TL;DR: Electrical measurements show that the observed optical emission originates from radiative recombination of electrons and holes that are simultaneously injected into the undoped nanotubes, consistent with a nanotube FET model in which thin Schottky barriers form at the source and drain contacts.
Abstract: Polarized infrared optical emission was observed from a carbon nanotube ambipolar field-effect transistor (FET). An effective forward-biased p-n junction, without chemical dopants, was created in the nanotube by appropriately biasing the nanotube device. Electrical measurements show that the observed optical emission originates from radiative recombination of electrons and holes that are simultaneously injected into the undoped nanotube. These observations are consistent with a nanotube FET model in which thin Schottky barriers form at the source and drain contacts. This arrangement is a novel optical recombination radiation source in which the electrons and holes are injected into a nearly field-free region. Sucha source may form the basis for ultrasmall integrated photonic devices.
926 citations
TL;DR: In this article, a broad visible and infrared photoluminescence continuum is detected from surface-plasmon-enhanced transitions in gold nanostructures, and the infrared signal is only present for surfaces with nanometer-scale roughness.
Abstract: A broad visible and infrared photoluminescence continuum is detected from surface-plasmon-enhanced transitions in gold nanostructures. We find that the ratio of generated infrared to visible emission is much stronger for gold nanostructures than for smooth gold films. While visible emission is well explained by interband transitions of d-band electrons into the conduction band and subsequent radiative recombination, the strong infrared emission cannot be accounted for by the same mechanism. We propose that the infrared emission is generated by intraband transitions mediated by the strongly confined fields near metal nanostructures (localized surface plasmons). These fields possess wave numbers that are comparable to the wave numbers of electrons in the metal, and the associated field gradients give rise to higher-order multipolar transitions. We compare photoluminescence spectra for single gold spheres, smooth and rough gold films, and sharp gold tips and demonstrate that the infrared signal is only present for surfaces with nanometer-scale roughness.
609 citations
TL;DR: In this paper, the authors describe methods for analysis of edge-emitted amplified spontaneous emission spectra measured as a function of the pumped stripe length, and show that both the modal gain and the unamplified spontaneous emission spectrum can be extracted from the data, and describe a means of calibrating the spontaneous emission in real units, without requiring the carrier populations to be described by Fermi functions.
Abstract: In this paper, we describe methods for analysis of edge-emitted amplified spontaneous emission spectra measured as a function of the pumped stripe length. We show that both the modal gain and the unamplified spontaneous emission spectra can be extracted from the data, and we describe a means of calibrating the spontaneous emission in real units, without requiring the carrier populations to be described by Fermi functions. The gain and emission spectra can be determined for transverse electric and transverse magnetic polarizations and by summing the recombination currents for each polarization the total radiative current can be measured. This enables the overall internal radiative quantum efficiency to be calculated. Once the calibration factor is known the internal stimulated recombination rate at the facet can also be estimated. The experiment can be configured to give a measurement of the passive modal absorption of the gain medium. The internal optical mode loss can be determined from the long-wavelength region of the gain spectrum or the modal absorption spectrum. In summary, we show that measurements of amplified spontaneous emission spectra provide a full characterization of the gain medium.
223 citations
TL;DR: In this paper, the authors reported large external photoluminescence quantum efficiencies of textured bulk crystalline silicon wafers of up to 10.2% at T =130 K and of 6.1% at room temperature.
Abstract: Due to its indirect bandstructure, bulk crystalline silicon is generally regarded as a poor light emitter. In contrast to this common perception, we report here on surprisingly large external photoluminescence quantum efficiencies of textured bulk crystalline silicon wafers of up to 10.2% at T=130 K and of 6.1% at room temperature. Using a theoretical model to calculate the escape probability for internally generated photons, we can conclude from these experimental figures that the radiative recombination probability or internal luminescence quantum efficiency exceeds 20% at room temperature.
177 citations
TL;DR: In this paper, the effect of light forces on atoms when the field is enclosed in an optical resonator of high finesse is discussed, and the authors identify the dynamical coupling between the light field intensity and the atomic motion as the central mechanism underlying the cavity-induced cooling.
Abstract: We review the modifications and implications of the effect of light forces on atoms when the field is enclosed in an optical resonator of high finesse. The systems considered range from a single atom strongly coupled to a single mode of a high-Q microcavity to a large ensemble of atoms in a highly degenerate quasi-confocal resonator. We set up general models that allow us to obtain analytic expressions for the optical potential, friction, and diffusion. In the bad-cavity limit the modified cooling properties can be attributed to the spectral modifications of light absorption and spontaneous emission in a form of generalized and enhanced Doppler cooling. For the strong coupling regime in a good cavity, we identify the dynamical coupling between the light field intensity and the atomic motion as the central mechanism underlying the cavity-induced cooling. The dynamical cavity cooling, which does not rely on spontaneous emission, can be enhanced by multimode cavity geometries because of the effect of coherent photon redistribution between different modes. The model is then generalized to include several distinct frequencies to account for more general trap geometries. Finally we show that the field-induced buildup of correlations between the motion of different particles plays a central role in the scaling behavior of the system. Depending on the geometry and parameters, its effect ranges from strong destructive interference, slowing down the cooling process, to self-organized crystallization, implying atomic self-trapping and faster cooling to lower temperatures by cooperative coherent scattering.
175 citations
TL;DR: A hybrid 2D-3D photonic band gap (PBG) heterostructure which enables both complete control of spontaneous emission of light from atoms and planar light-wave propagation in engineered wavelength-scale microcircuits is introduced.
Abstract: We introduce the concept of a hybrid 2D-3D photonic band gap (PBG) heterostructure which enables both complete control of spontaneous emission of light from atoms and planar light-wave propagation in engineered wavelength-scale microcircuits. Using three-dimensional (3D) light localization, this heterostructure enables flow of light without diffraction through micron-scale air waveguide networks. Achieved by intercalating two-dimensional photonic crystal layers containing engineered defects into a 3D PBG material, this provides a general and versatile solution to the problem of "leaky modes" and diffractive losses in integrated optics.
153 citations
TL;DR: In this article, the authors present a comprehensive theoretical and experimental analysis of 1.3/spl mu/m InGaAsN/GaAs laser devices and show that the threshold current is dominated by nonradiative, defect-related recombination.
Abstract: We present a comprehensive theoretical and experimental analysis of 1.3-/spl mu/m InGaAsN/GaAs lasers. After introducing the 10-band k /spl middot/ p Hamiltonian which predicts transition energies observed experimentally, we employ it to investigate laser properties of ideal and real InGaAsN/GaAs laser devices. Our calculations show that the addition of N reduces the peak gain and differential gain at fixed carrier density, although the gain saturation value and the peak gain as a function of radiative current density are largely unchanged due to the incorporation of N. The gain characteristics are optimized by including the minimum amount of nitrogen necessary to prevent strain relaxation at the given well thickness. The measured spontaneous emission and gain characteristics of real devices are well described by the theoretical model. Our analysis shows that the threshold current is dominated by nonradiative, defect-related recombination. Elimination of these losses would enable laser characteristics comparable with the best InGaAsP/InP-based lasers with the added advantages provided by the GaAs system that are important for vertical integration.
145 citations
TL;DR: In this article, a single-photon source based on a quantum dot in a micropost microcavity was demonstrated, which exhibits a large Purcell factor together with a small multiphoton probability.
Abstract: We demonstrate a single-photon source based on a quantum dot in a micropost microcavity that exhibits a large Purcell factor together with a small multiphoton probability. For a quantum dot on resonance with the cavity, the spontaneous emission rate is increased by a factor of 5, while the probability to emit two or more photons in the same pulse is reduced to 2% compared to a Poisson-distributed source of the same intensity. In addition to the small multiphoton probability, such a strong Purcell effect is important in a single-photon source for improving the photon outcoupling efficiency and the single-photon generation rate, and for bringing the emitted photon pulses closer to the Fourier transform limit.
145 citations
TL;DR: In this article, the authors theoretically analyzed the Purcell effect at room temperature by using the four-level rate equations that include the intraband relaxation and the non-radiative effect, and confirmed that the carrier lifetime was shortened to 1/10 of that in the as-grown epitaxial wafer at a low pump level.
Abstract: In this paper, we discuss the Purcell effect, which enhances the spontaneous emission rate, in microdisk lasers operating at room temperature by continuous wave photopumping. We theoretically analyzed the Purcell effect at room temperature by using the four-level rate equations that include the intraband relaxation and the nonradiative effect. We also fabricated 1.55-/spl mu/m GaInAsP microdisk lasers with a minimum diameter of 1.7 /spl mu/m and a minimum threshold power of 19 /spl mu/W. Then, we measured the carrier lifetime in a 2.6-/spl mu/m-diameter device by the phase-resolved spectroscopy method, and confirmed that the carrier lifetime was shortened to 1/10 of that in the as-grown epitaxial wafer at a low pump level. From the comparison between the theory and the experiment, we estimated the Purcell factor to be 6.7, the spontaneous emission factor to be 0.11, and the nonradiative lifetime to be 4 ns. The nonradiative lifetime was consistent with that estimated by another methods. We believe that this is the first demonstration of the Purcell effect in semiconductor microcavities at room temperature.
144 citations
TL;DR: In this article, an asymptotic expression for the spectrum of spontaneous x-ray emission from an axisymmetric monoenergetic electron beam is derived and three-dimensional particle-in-cell simulations of a 25-GeV electron bunch propagating in a laser-produced ion channel are mad...
Abstract: X-ray generation by relativistic electrons in an ion channel is studied. The emission process is analyzed in the regime of high harmonic generation when the plasma wiggler strength is large. Like for the conventional free electron laser, the synchrotron-like broadband spectrum is generated in this regime. An asymptotic expression for the radiation spectrum of the spontaneous emission is derived. The radiation spectrum emitted from an axisymmetric monoenergetic electron beam is analyzed. The stimulated emission in the ion channel is studied and the gain of the ion-channel synchrotron-radiation laser is calculated. It is shown that the use of laser-produced ion channels leads to a much higher power of x-ray radiation than the one in a self-generated channel. In addition, the mean photon energy, the number of emitted photons and the brilliance of the photon beam increase dramatically. Three-dimensional particle-in-cell simulations of a 25-GeV electron bunch propagating in a laser-produced ion channel are mad...
TL;DR: Vertical-cavity surface-emitting lasers subjected to weak polarization-insensitive optical feedback are studied experimentally and theoretically and it is found that the feedback induces random anticorrelated hopping between the two orthogonal linearly polarized modes.
Abstract: Vertical-cavity surface-emitting lasers subjected to weak polarization-insensitive optical feedback are studied experimentally and theoretically. We find that the feedback induces random anticorrelated hopping between the two orthogonal linearly polarized modes. This polarization mode hopping is accompanied by rapid anticorrelated oscillations in the linearly polarized intensities at the external-cavity frequency. The study of a simple stochastic delay differential equation suggests that these oscillations generated by the delay are typical of any hopping phenomenon between states.
01 Jan 2003
TL;DR: In this paper, the authors reviewed the development of cavity-quantum electro- dynamics experiments in all semiconductor microcavities using self-assembled quan- tum dots as "artificial atoms" and discussed several major issues for future work, such as the quest for a strong coupling regime for single quantum dots in cavities and the feasibility and performances of single QD lasers.
Abstract: In this contribution, the recent development of cavity-quantum electro- dynamics experiments in all semiconductor microcavities using self-assembled quan- tum dots as "artificial atoms" is reviewed. In the weak coupling regime, a strong enhancement of the spontaneous emission rate (Purcell effect) can be observed for collection of dots as well as single dots. This effect permits to achieve a regime of "nearly" singlemode spontaneous emission and is the key for the efficient operation of the first solid-state singlemode single photon source, which is based on a single quantum dot in a pillar microcavity. Several major issues for future work, such as the quest for a strong coupling regime for single quantum dots in cavities and the feasibility and performances of single QD lasers are also discussed.
TL;DR: It is demonstrated that a continuously measured microelectronic circuit, the Cooper-pair box measured by a radio-frequency single-electron transistor, approximates a quantum two-level system.
Abstract: We demonstrate that a continuously measured microelectronic circuit, the Cooper-pair box measured by a radio-frequency single-electron transistor, approximates a quantum two-level system. We extract the Hamiltonian of the circuit through resonant spectroscopy and measure the excited-state lifetime. The lifetime is more than 10(5) times longer than the inverse transition frequency of the two-level system, even though the measurement is active. This lifetime is also comparable to an estimate of the known upper limit, set by spontaneous emission, for this circuit.
TL;DR: In this article, the authors proposed to use Si nanocrystallites, nanowires, and alloying with Ge and crystal strain methods to achieve the carrier confinement required to boost radiative recombination efficiency.
Abstract: Research on efficient light emission from silicon devices is moving toward leading-edge advances in components for nano-optoelectronics and related areas. A silicon laser is being eagerly sought and may be at hand soon. A key advantage is in the use of silicon-based materials and processing, thereby using high yield and low-cost fabrication techniques. Anticipated applications include an optical emitter for integrated optical circuits, logic, memory, and interconnects; electro-optic isolators; massively parallel optical interconnects and cross connects for integrated circuit chips; lightwave components; high-power discrete and array emitters; and optoelectronic nanocell arrays for detecting biological and chemical agents. The new technical approaches resolve a basic issue with native interband electro-optical emission from bulk Si, which competes with nonradiative phonon- and defect-mediated pathways for electron-hole recombination. Some of the new ways to enhance optical emission efficiency in Si diode devices rely on carrier confinement, including defect and strain engineering in the bulk material. Others use Si nanocrystallites, nanowires, and alloying with Ge and crystal strain methods to achieve the carrier confinement required to boost radiative recombination efficiency. Another approach draws on the considerable progress that has been made in high-efficiency, solar-cell design and uses the reciprocity between photo- and light-emitting diodes. Important advances are also being made with silicon-oxide materials containing optically active rare-earth impurities.
TL;DR: The optical properties of laser-induced plasma generated firm solid and liquid samples expanded across an external, steady magnetic field have been studied by atomic-emission spectroscopy and enhanced emission was found to be due to an increase in effective density of the plasma as a result of magnetic confinement when the plasma cooled after expansion.
Abstract: The optical properties of laser-induced plasma generated firm solid (Al alloy) and liquid (Mn, Cr, Mg, or Ti solutions) samples expanded across an external, steady magnetic field have been studied by atomic-emission spectroscopy. Various line emissions obtained from the constituents of the Al alloy and of the aqueous solution show an enhancement in intensity in the presence of an approximately 5-kG magnetic field. The enhancement of the signal was nearly a factor of 2 for the minor constituents of the solid samples and a factor of 1.5 for the elements in liquid phase. Temporal evolution of the emission from the solid sample showed maximum enhancement in emission intensity at 3-10-micros time delay after plasma formation in the laser energy range 10-50 mJ. However, for the liquid sample the maximum signal was for a gate delay of 3-25 micros the energy range 50-200 mJ. This enhancement in the emission intensity was found to be due to an increase in effective density of the plasma as a result of magnetic confinement when the plasma cooled after expansion. This enhanced emission was due to an increase in the rate of radiative recombination in the plasma.
TL;DR: In this paper, the quantum resonances occurring with δ-kicked atoms when the kicking period is an integer multiple of the half-Talbot time are analyzed in detail.
Abstract: The quantum resonances occurring with δ-kicked atoms when the kicking period is an integer multiple of the half-Talbot time are analysed in detail. Exact results about the momentum distribution at exact resonance are established, both in the case of totally coherent dynamics and in the case when decoherence is induced by spontaneous emission. A description of the dynamics when the kicking period is close to, but not exactly at resonance, is derived by means of a quasi-classical approximation where the detuning from exact resonance plays the role of the Planck constant. In this way scaling laws describing the shape of the resonant peaks are obtained. Such analytical results are supported by extensive numerical simulations, and explain some recent surprising experimental observations.
TL;DR: In this paper, the optical detection of single atoms held in a microscopic atom trap close to a surface is investigated. And the results suggest that with present-day technology microcavities can be built around the atom with sufficiently high finesse to permit unambiguous detection of a single atom in the trap with 10 µs of integration.
Abstract: We investigate the optical detection of single atoms held in a microscopic atom trap close to a surface. Laser light is guided by optical fibers or optical microstructures via the atom to a photodetector. Our results suggest that with present-day technology microcavities can be built around the atom with sufficiently high finesse to permit unambiguous detection of a single atom in the trap with 10 µs of integration. We compare resonant and nonresonant detection schemes and discuss the requirements for detecting an atom without causing it to undergo spontaneous emission.
TL;DR: In this article, the authors studied collective spontaneous emission from a linear array of N two-state atoms using quantum trajectory theory and without an a priori single-mode assumption, and investigated the evolution of the distribution from a dipole radiation pattern for the first photon emission to a distribution characteristic of directional superradiance.
Abstract: We study collective spontaneous emission from a linear array of N two-state atoms using quantum trajectory theory and without an a priori single-mode assumption. Assuming a fully excited initial state, we calculate the angular distribution of the $k\mathrm{th}$ emitted photon, $k=1,\dots{},N.$ We investigate the evolution of the distribution from a dipole radiation pattern for the first photon emission to a distribution characteristic of directional superradiance. The formalism is developed around an unravelling of the master equation in terms of source-mode quantum jumps. Exact calculations for 11 and fewer atoms do not show directional superradiance, but are characterized by delayed (subradiant) photon emissions directed along the axis of the linear array. A modified boson approximation is made to treat the many-atom case, where it is found that strong directional superradiance occurs for a few hundred atoms; the decay of subradiant excitations is preserved in the tail of the superradiant pulse.
Book•
01 Aug 2003
TL;DR: In this article, the authors present a simple design of VLSs and a simple characterization of the properties of the VLS with respect to thermal, electrical and nonlinear properties.
Abstract: Preface.Acknowledgments.1. Vertical Cavity Surface Emitting Lasers - An overview.2. Simple Design Consideration of Vertical Cavity Surface Emitting Lasers.3. Modal Characteristics of Vertical Cavity Surface Emitting Lasers.4. Polarization Properties of Vertical Cavity Surface Emitting Lasers.5. Thermal Characteristics of Vertical Cavity Surface Emitting Lasers.6. Electrical Characteristics of Vertical Cavity Surface Emitting Lasers.7. Direct Modulation of Vertical Cavity Surface Emitting Lasers.8. Spontaneous Emission of Vertical Cavity Surface Emitting Lasers.9. Nonlinear Characteristics in Vertical Cavity Surface Emitting Lasers. Index.
TL;DR: In this article, a fully microscopic model is used to calculate absorption/gain and spontaneous emission for GaInNAs quantum-well laser gain media, which can be used to derive the optical properties for the regime of semiconductor laser operation from low density photo luminescence spectra.
Abstract: A fully microscopic model is used to calculate absorption/gain and spontaneous emission for GaInNAs quantum-well laser gain media. It is demonstrated how this approach can be used to derive the optical properties for the regime of semiconductor laser operation from low density photo luminescence spectra which can be obtained from simple experiments. Numerical results are presented showing that increased well depth leads to strongly increased differential gains and gain amplitudes and pronounced shifts of the gain maximum with increasing density. On the basis of a quantum Blotzmann model for the incoherent carrier dynamics it is shown, that high carrier confinement can lead to unusually long carrier capture times. Furthermore, temperature dependent bandstructure parameters for GaInNAs for the applied 10-band k · p -model are presented that have been derived from comparison to recent experimental data.
TL;DR: In this article, the authors demonstrate coherent control of spontaneous emission for a three-level atom located within a photonic band gap (PBG) material, with one resonant frequency near the edge of the PBG.
Abstract: We demonstrate the coherent control of spontaneous emission for a three-level atom located within a photonic band gap (PBG) material, with one resonant frequency near the edge of the PBG. Spontaneous emission from the three-level atom can be totally suppressed or strongly enhanced depending on the relative phase between the steady-state control laser coupling the two upper levels and the pump laser pulse used to create an excited state of the atom in the form of a coherent superposition of the two upper levels. Unlike the free-space case, the steady-state inversion of the atomic system is strongly dependent on the externally prescribed initial conditions. This non-zero steady-state population is achieved by virtue of the localization of light in the vicinity of the emitting atom. It is robust to decoherence effects provided that the Rabi frequency of the control laser field exceeds the rate of dephasing interactions. As a result, such a system may be relevant for a single-atom, phase-sensitive optical memory device on the atomic scale. The protected electric dipole within the PBG provides a basis for a qubit to encode information for quantum computations. A detailed literature survey on the nature, fabrication and applications of PBG materials is presented to provide context for this research.
TL;DR: In this paper, the steady-state spontaneous emission of a V-type three-level atom was investigated, with the coherence between the two upper levels modified and controlled via incoherent pumping to a fourth auxiliary level.
Abstract: We investigate the steady-state spontaneous emission of a V-type three-level atom, with the coherence between the two upper levels modified and controlled via incoherent pumping to a fourth auxiliary level. The external pumping gives us an easily controllable handle in manipulating the spontaneous emission to such an extent that, under certain conditions, complete quenching of spontaneous emission is possible. We also show that even the interference between the decay channels, which is considered a key requirement in spontaneous emission quenching through quantum interference, is not essential to achieve near 100% trapping and almost complete suppression of spontaneous emission. Thus we provide a scheme for spontaneous emission quenching which can be easily realized experimentally.
TL;DR: In this article, a selfconsistent numerical Poisson-Schrodinger-drift-diffusion solver is described for simulation of multiple-quantum-well (MQW) Al/sub x/Ga/sub 1-x/As-GaAs solar cells.
Abstract: A self-consistent numerical Poisson-Schrodinger-drift-diffusion solver is described for simulation of multiple-quantum-well (MQW) Al/sub x/Ga/sub 1-x/As-GaAs solar cells. The rates of escape, capture, and recombination of photoexcited carriers in quantum wells embedded in the intrinsic region of a p-i-n device are self-consistently incorporated in the model. The performance of the device for various quantum-well configurations is investigated and the device characteristics are related to the dynamics of capture, escape, absorption, and recombination of carriers in the quantum wells. Our results show that the incorporation of MQWs in the intrinsic region of a p-i-n solar cell can improve the conversion efficiency of non-optimal devices, if the device is designed based on careful consideration of the behavior of the photoexcited carriers in the quantum wells. Specifically, we found out that an Al/sub 0.1/Ga/sub 0.9/As-GaAs cell with multiple quantum wells of 150 /spl Aring/ is more efficient than an identical single bandgap Al/sub 0.1/Ga/sub 0.9/As cell with no quantum wells, but less efficient than a single bandgap GaAs cell without such quantum wells.
TL;DR: In this article, a single quantum dot was used in a micropost microcavity to generate triggered single photons, which led to a large enhancement of spontaneous emission rate and allowed for strong coupling and single-dot lasing.
Abstract: We have used a single quantum dot in a micropost microcavity to generate triggered single photons. Coupling between the quantum-dot dipole and the confined microcavity mode leads to a large enhancement of the spontaneous emission rate. This, in turn, leads to efficient coupling of the emitted photons into a single traveling-wave mode. Optimization of the microcavity design should lead to nearly unity efficiency, and could also allow for strong coupling and for single-dot lasing.
TL;DR: In this paper, a 3-nitride VCSEL with dielectric distributed Bragg reflectors (DBRs) was constructed by removing a SiC substrate from a III-nitric cavity with a dry etching technique and then wafer bonding the cavity and SiO2/ZrO2 DBRs.
Abstract: Lasing action is achieved in InGaN vertical-cavity surface-emitting lasers (VCSELs) with dielectric distributed Bragg reflectors (DBRs). We fabricated III-nitride VCSELs by removing a SiC substrate from a III-nitride cavity with a dry etching technique and then wafer bonding the cavity and SiO2/ZrO2 DBRs. These VCSELs have a high quality factor of 460 and a spontaneous emission factor of 10−2. We observed lasing at a wavelength of 401 nm at room temperature with optical pumping. This lasing action was demonstrated at a low threshold of 5.1 mJ/cm2 by using a high-quality crystalline cavity and quantum-well layers without surface roughening or cracking.
TL;DR: In this paper, the spontaneous emission of colloidal CdSe quantum dots embedded in a half-wavelength one-dimensional cavity was shown to be enhanced by a factor of 2.7.
Abstract: We demonstrate an enhancement of the spontaneous emission from colloidal CdSe quantum dots embedded in a half-wavelength one-dimensional cavity. When embedded in the cavity, the emission of the quantum dots is enhanced by a factor of 2.7. We also show a strong amplification by one order of magnitude in the absorption of the CdSe quantum dots due to the cavity effect.
TL;DR: In this article, a numerical model that accounts for the effects of amplified spontaneous emission (ASE) on the carrier dynamics in a traveling wave semiconductor optical amplifier is presented, and the ASE is modeled using effective parameters that are derived starting from the spontaneous emission and gain models.
Abstract: A numerical model that accounts for the effects of the amplified spontaneous emission (ASE) on the carrier dynamics in a travelling wave semiconductor optical amplifier is presented. The ASE is modeled using effective parameters that are derived starting from the spontaneous emission and gain models. The gain dynamics are then analyzed using the parameters extracted from measurements on a real device to explain the overshoot in the gain recovery. The model is also used to simulate the gain recovery in a three-wavelength device configuration for various injected powers and wavelengths. The recovery time when the injected beam is at the device transparency wavelength is also analyzed with particular attention to the differences between co- and counter-propagating configurations.
09 Jul 2003
TL;DR: An overview of planar resonant-cavity light-emitting diodes is presented in this article, where state-of-the-art devices in different semiconductor material systems and at different wavelengths are reviewed.
Abstract: An overview of planar resonant-cavity light-emitting diodes is presented. Letting spontaneous emission happen in a planar cavity will in the first place affect the extraction efficiency. The internal intensity distribution is not longer isotropic due to interference effects (or density of states effects). The basics of dipole emission in planar cavities will be shortly reviewed using a classical approach valid in the so called weak-coupling regime. The total emission enhancement or Purcell factor, although small in planar cavities, will be explained. The design of a GaAs/AlGaAs RCLED is discussed. We review the state-of-the-art devices in different semiconductor material systems and at different wavelengths. Some advanced techniques based on gratings or photonic crystals to improve the efficiency of these devices are discussed. RCLEDs are not the only candidates that can be used as high-efficiency light sources in communication and non-communication applications. They compete with other high-efficiency LEDs and with VCSELs. The future prospects of RCLEDs are discussed in view of this competition.
TL;DR: In this paper, an experimental and theoretical investigation into the low-frequency intensity noise characteristics of erbium-doped distributed feedback (DFB) fiber lasers is presented along with the characteristics of the grating and doped fibers.
Abstract: We present an experimental and theoretical investigation into the low-frequency intensity noise characteristics of erbium-doped distributed feedback (DFB) fiber lasers. The intensity noise characteristics of six nonidentical erbium-doped DFB fiber lasers are presented along with the characteristics of the grating and doped fibers. An analytical model has been used to predict the intensity noise generated in a linear fiber laser and explain the observed noise characteristics. Overall we find good agreement between our analytical model and observations. In particular, we find the intensity noise at frequencies close to the relaxation oscillation frequency significantly elevated due to excess noise from either spontaneous emission or cavity loss modulation. These results can be used to optimize the fiber laser design for sensor applications.