Showing papers on "Quantum well published in 1995"

High-brightness InGaN blue, green and yellow light-emitting diodes with quantum well structures

Abstract: High-brightness blue, green and yellow light-emitting diodes (LEDs) with quantum well structures based on III-V nitrides were grown by metalorganic chemical vapor deposition on sapphire substrates. The typical green LEDs had a peak wavelength of 525 nm and full width at half-maximum (FWHM) of 45 nm. The output power, the external quantum efficiency and the luminous intensity of green LEDs at a forward current of 20 mA were 1 mW, 2.1% and 4 cd, respectively. The luminous intensity of green LEDs (4 cd) was about 40 times higher than that of conventional green GaP LEDs (0.1 cd). Typical yellow LEDs had a peak wavelength of 590 nm and FWHM of 90 nm. The output power of yellow LEDs was 0.5 mW at 20 mA. When the emission wavelength of III-V nitride LEDs with quantum well structures increased from the region of blue to yellow, the output power decreased dramatically.

Superbright Green InGaN Single-Quantum-Well-Structure Light-Emitting Diodes

Abstract: Superbright green InGaN single quantum well (SQW) structure light-emitting diodes (LEDs) with a luminous intensity of 12 cd were fabricated The luminous intensity of these green InGaN SQW LEDs (12 cd) was about 100 times higher than that of conventional green GaP LEDs (01 cd) The output power, the external quantum efficiency, the peak wavelength and the full width at half-maximum of green SQW LEDs were 3 mW, 63%, 520 nm and 30 nm, respectively, at a forward current of 20 mA The p-AlGaN/InGaN/n-GaN structure of green InGaN SQW LEDs were grown by metalorganic chemical vapor deposition on sapphire subsutrates

High‐power InGaN single‐quantum‐well‐structure blue and violet light‐emitting diodes

Abstract: High‐power blue and violet light‐emitting diodes(LEDs) based on III–V nitrides were grown by metalorganic chemical vapor deposition on sapphire substrates. As an active layer, the InGaN single‐quantum‐well‐structure was used. The violet LEDs produced 5.6 mW at 20 mA, with a sharp peak of light output at 405 nm, and exhibited an external quantum efficiency of 9.2%. The blue LEDs produced 4.8 mW at 20 mA and sharply peaked at 450 nm, corresponding to an external quantum efficiency of 8.7%. These values of the output power and the quantum efficiencies are the highest ever reported for violet and blue LEDs.

Type‐II quantum‐well lasers for the mid‐wavelength infrared

Abstract: We discuss an improved mid‐wave infrared diode laser structure based on InAs‐Ga1−xInxSb‐ InAs‐Ga1−xAlxSb Type‐II multiple quantum wells. The proposed design combines strong optical coupling, 2D dispersion for both electrons and holes, suppression of the Auger recombination rate, and excellent electrical and optical confinement.

Ultralow threshold current vertical-cavity surface-emitting lasers obtained with selective oxidation

Abstract: The authors report InGaAs single quantum well vertical-cavity surface-emitting lasers with an intracavity p-contact fabricated by selective oxidation of AlAs and distributed Bragg reflectors composed of binary materials (AlAs/GaAs). Record low threshold currents of 8.7 µA in ~3 µm square devices and 140 µA in 10 µm square devices with maximum output powers over 1.2 mW are achieved.

Ultrafast coherent control and destruction of excitons in quantum wells.

Abstract: We demonstrate the coherent destruction of photogenerated excitons in semiconductor quantum wells within a few hundred femtoseconds of their excitation. Coherent control of carrier dynamics is achieved with phase-locked pairs of 100 fs infrared pulses. The technique induces an optical response which is faster than the inverse of the exciton linewidth superseding Fourier limits for a single pulse. Energy selectivity enables the coherent transfer of angular momentum between hole states. Such phase-tailored pulse trains can be utilized to investigate the generation process and intermediate virtual states in quantum structures.

Phase-controlled currents in semiconductors.

Abstract: The direction of emission of photoexcited electrons in semiconductors is controlled by adjusting the relative phase difference between a midinfrared radiation and its second harmonic. This is achieved by using quantum interference of electrons produced with one- and two-photon bound-to-free intersubband transitions in AlGaAs/GaAs quantum well superlattices.

Superlattices and Other Heterostructures: Symmetry and Optical Phenomena

Abstract: 1 Quantum Wells and Superlattices.- 2 Crystal Symmetry.- 2.1 Symmetry Operations, Groups.- 2.2 Point-Group Classification.- 2.3 Space Groups.- 2.4 Group Representations, Characters.- 2.5 Point-Group Representations.- 2.6 Spinor Representations.- 2.7 Representations of Space Groups.- 2.8Invariance Under Time Inversion.- 2.9 Selection Rules.- 2.10 Determination of Linearly Independent Components of Material Tensors.- 3 Electron Spectrum in Crystals, Quantum Wells and Superlattices.- 3.1 The k-p Method.- 3.2 The Effective-Mass Method Deformation Potential.- 3.3 Method of Invariants.- 3.4 Electron and Hole Spectrum in Diamond-and Zincblende-Type Cubic Crystals.- 3.5 Electron Spectra of Quantum Wells and Superlattices.- 3.6 Hole Spectrum in Quantum Wells and Superlattices for Degenerate Bands.- 3.7 Deformed and Strained Superlattices.- 3.8 Quantum Wells and Superlattices in a Magnetic Field.- 3.9 Spectrum of Quantum Wells and Superlattices in an Electric Field.- 4 Vibrational Spectra of Crystals and Superlattices Electron-Phonon Interaction.- 4.1 Normal Vibrations: Distribution in Irreducible Representations.- 4.2 Vibrational Spectra of Superlattices.- 4.3 Electron-Phonon Interaction.- 5 Localized Electron States and Excitons in Heterostructures.- 5.1 Shallow Impurity Centers.- 5.2 Localized States at Superlattice Defects.- 5.3 Excitons.- 5.4 Exchange Splitting of Exciton Levels.- 6 Interband Optical Transitions.- 6.1 Optical Superlattices.- 6.2 Interband Transitions and Dielectric Susceptibility of a Periodic Heterostructure.- 6.3 Coulomb Interaction Between the Electron and the Hole.- 6.4 Exciton Polaritons in an Optical Superlattice.- 6.5 Light Reflection.- 6.6 Electro-Optical Effects in Interband Transitions.- 6.7 Magneto-Optical Spectra.- 7 ntraband Transitions.- 7.1 Cyclotron Resonance and Effective Electron Mass.- 7.2 Intersubband Absorption.- 7.3 Electron-Spin Resonance.- 7.4 IR Reflection in an Undoped Superlattice.- 8 Light Scattering.- 8.1 Theory of Light Scattering in Semiconductors.- 8.2 Scattering by Intersubband Excitations.- 8.3 Scattering by Acoustical Phonons with a Folded Dispersion Law.- 8.4 Scattering by Optical Phonons in Heterostructures.- 8.5 Acceptor Spin-Flip Raman Scattering.- 9 Polarized Luminescence in Quantum Wells and Superlattices.- 9.1 Luminescence as a Tool to Study Electronic Spectra and Kinetic Processes in Two-Dimensional Systems.- 9.2 Luminescence in the Quantum Hall Regime, Quantum Beats.- 9.3 Optical Spin Orientation and Alignment of Electron Momenta.- 9.4 Optical Orientation and Alignment of Excitons.- 9.5 Polarized Luminescence of Excitons and Impurities in an External Magnetic Field.- 10 Nonlinear Optics.- 10.1 Two-Photon Absorption.- 10.2 Photoreflectance.- 10.3 Diffraction from a Light-Induced Spatial Grating.- 10.4 Third-Harmonic Generation.- 10.5 Linear and Circular Photogalvanic (Photovoltaic) Effects.- 10.6 Current of Optically Oriented Electrons.- 10.7 Photon Drag Current.

1.3 μm photoluminescence from InGaAs quantum dots on GaAs

Abstract: We use molecular beam epitaxy to grown coherently strained InGaAs islands on (100) GaAs substrates. The islands show room‐temperature photoluminescence at 1.3 μm with a full width at half‐maximum of only 28 meV. The integrated photoluminescence intensity is comparable to that of a quantum well. The islands are formed by depositing 22 monolayers of In0.3Ga0.7As with alternating beams of In, Ga, and As2. Atomic force microscopy measurements show that the islands are ellipsoidal sections with an average peak height of 24 nm. The intersection of the islands with the (100) plane is an ellipse whose major axis is along [011] and has a mean length of 54 nm, and whose minor axis is along [011] and has a mean length of 36 nm. The islands form a dense array with an areal coverage of about 40%.

Photoluminescence and electroluminescence of SiGe dots fabricated by island growth

Abstract: We present a study of photo‐ and electroluminescence of SiGe dots buried in Si and compare them with structures containing smooth SiGe layers. The SiGe dot structures were fabricated by low‐pressure chemical vapor deposition using the Stranski–Krastanov growth mode (island growth). We show that the localization of excitons in the dots leads to an increase of the luminescence efficiency at low excitation compared to smooth SiGe layers (e.g., quantum wells). At higher excitation the efficiency decreases which is attributed to nonradiative Auger recombination processes in the dots.

Exciton condensate in semiconductor quantum well structures.

Abstract: We propose that the exciton condensate may form in a well-controlled way in appropriately arranged semiconductor quantum well structures. The mean-field theory of Keldysh and Kopaev, exact in both the high density and low density limits, is solved numerically to illustrate our proposal. The electron-hole pairing gap and the excitation spectrum of the exciton condensate are obtained. The energy scales of the condensate are substantial at higher densities. We discuss how such densities could be achieved experimentally by generating an effective pressure.

Stimulated Emission by Current Injection from an AlGaN/GaN/GaInN Quantum Well Device

Abstract: Quantum well structures composed of GaInN well and GaN barrier were fabricated. Room-temperature stimulated emission by pulsed current injection is observed from group III nitride using the very thin active layer, for the first time.

Confined Electrons and Photons

Abstract: The scientific fields of confined electrons and photons have become areas of major efforts worldwide. Their appeal originates in the many facets they offer in fundamental and applied science, in technology and device development, and to high technology, large-scale industries.

Vertical transition quantum cascade laser with bragg confined excited state

Abstract: A new midinfrared (λ∼4.5 μm) intersubband quantum cascade laser based on a vertical transition is reported. A superlattice graded gap region was incorporated in the design to provide strong electron confinement in the upper state using a Bragg reflector. Pulsed operation at 100 K is reported with a threshold current density of Jth=3 kA/cm2 and a measured slope efficiency of 300 mW/A.

Confined electrons and photons : new physics and applications

Abstract: Confined Electrons and Photons: A Summary:.- Basic Solid State Optics in Bulk and 2D Structures.- Dynamics of Optical Excitations in Semiconductors.- Optical Transitions, Excitons and Polaritons in Bulk and Low-Dimensional Semiconductor Structures.- Electron States in Biased Heterostructures.- Phonons and Electron-Phonon Interaction in Low-Dimensional Structures.- Excitonic Radiative Dynamics in Semiconductor Quantum Wells.- Superlattices and Quantum Wells in Organic Semiconductors: Excitons and Optical Non-linearities.- Intersubband Transitions in Quantum Wells.- Confined Electrons in 1D and 0D.- Principles of Electron Solid State Electron Optics.- Atomic-like Spectroscopy of Low Dimensional Electron Systems.- Inelastic Scattering and Thermalization in low-III-V Semiconductor Structures.- Synthesis and Spectroscopy of II-VI Quantum Dots: an Overview.- Prospects of High Efficiency Quantum Boxes obtained by direct epitaxial growth.- Confined Photons.- Atoms in Cavities.- Controlling Spontaneous Emission and Optical Microcavities.- Spontaneous Emission Control in Semiconductor Microcavities.- Strong Coupling in Semiconductor Microcavities.- Localization of Light in Disordered and Periodic Dielectrics.- Photonic Bloch Waves and Photonic Band Gaps.- Light Emission in Photonic Crystal Micro-Cavities.- Special Topics - Applications.- Semiconductor Nanostructure lasers: Fundamentals and Fabrications.- Quantum Wells Optical Switching Devices.- High-efficiency, Narrow Spectrum Resonant Cavity Light Emitting Diodes.- Short Papers (Seminars and Selected Posters).- Spontaneous Emission Control in Planar Structures: Er3+ in Si/SO2 Microcavities.- Vacuum Rabi Splitting in a Semiconductor Microcavity.- Impurity Modes in One-Dimensional Periodic Systems: The Transition from Photonic Bandgaps to Microcavities.- Photonic Bandgap Calculations: Inward and Outward Integral Equations and the KKR method.- Soliton-Polariton Interaction near an Excitonic Resonance in Semiconductors.- Dynamics of Excitons and Electron-Hole Plasma Confined in Semiconductor Nanocrystals.- Coupled-Quantum Wells for Optical Modulation.- In-plane Electro-Optic Effect in a Quantum Well.- Reprinted Papers: Basics.- Aspects of Polaritons.- Interband Optical Transitions in Extremely Anisotropic Semiconductors.- Effect of Retarded Interaction on the Exciton Spectrum in One-Dimensional and Two-Dimensional Crystals.- On the Exciton Luminescence at Low temperatures: Importance of the Polariton Viewpoint.- Spatial and Spectral Features of Polariton Fluorescence.- Reprinted Papers: Confined Electrons.- Studies of Exciton Localization in Quantum-Well Structures by Nonlinear-Optical Techniques.- Excitonic Optical Nonlinearity and Exciton Dynamics in Semiconductor Quantum Dots.- Very Large Optical Nonlinearity of Semiconductor Microcrystallites.- Reprinted Papers: Confined Photons.- Spontaneous Emission Probabilities at Radiofrequencies.- Inhibited Spontaneous Emission.- Inhibited Spontaneous Emission in Solid State Physics and Electronics.- Cavity Q.E.D.- Cavity Quantum Electrodynamics at Optical Frequencies.- Physics and Device Applications of Optical Microcavities.- Optical Processes in Microcavities.- Photon Number Squeezed States in Semiconductor Lasers.- Photonic Bandgap Structures.- Applications of Photonic Band gap Structures.- Contributors.

Vertical Cavity Surface Emitting Lasers

Abstract: Vertical cavity surface emitting laser (VCSEL) structures have been grown by both metal-organic chemical vapour deposition (MOCVD) and molecular beam epitaxy (MBE). These incorporate 3 strained InGaAs / GaAs quantum wells placed resonantly in a two wavelength long optical cavity, formed between AlAs / GaAs quarter wave dielectric reflector stacks through which current is injected. The reflection spectra of these stacks is studied in detail; the effects on the laser threshold gain of absorption due to impurities and of errors in growth are investigated. Methods of disruption of the AlAs / GaAs heterointerfaces have been used to reduce the operating voltage. The completed designs use 200A intermediate layers containing 30 or 50% aluminium or a superlattice graded region simpler than that used in previous designs. The effectiveness acceptor dopants; Be in MBE, C and Zn in MOCVD; is studied also. Modulation doping was employed to reduce the effects of optical absorption. Devices were fabricated into mesas by SiC14 reactive ion etching or defined by proton implant isolation. MBE grown devices were resonant at wavelengths in the range 950 to 1059mn with essentially constant (at —1020nm) eihhi transition energies in the wells. A detailed study of the wavelength variation of threshold current density Jth (X)was made. A minimum of 366A.cnr2 was measured at 1018nm in mesa devices. A similar relation is found for ion-implanted devices but the minimum is increased to 535A.cm-2 by incomplete isolation. Gain calculations, including strain effects, are used to explain the Jth(X) variation. Implanted devices offer superior c.w. performance due to reduced thermal and ohmic resistances. The relative offset between the gain spectrum and cavity resonance was examined for c.w. operation. It was found that carrier thermal effects limit the output power rather than shifts in the offset. The bias voltage of MOCVD grown devices is as low as 1.7V and the threshold current is as low as 764A.cm-2. This is higher than for MBE grown devices because of growth thickness errors and non-optimal alignment of the gain spectrum and cavity mode. The uniformity in emission wavelength is ±1% over 80% of a 2 inch diameter wafer, offering suitability for very large uniform arrays.

Low-loss intracavity AlAs/AlGaAs saturable Bragg reflector for femtosecond mode locking in solid-state lasers.

Abstract: We introduce a new low-loss semiconductor structure for femtosecond intracavity mode locking in low-gain solid-state lasers. This monolithic device can be engineered to exhibit specific saturation characteristics desirable for mode locking solid-state lasers. Self-starting 90-fs pulses are obtained with Ti:sapphire and diode-pumped Cr:LiSAF lasers. We discuss mode-locking mechanisms in quantum-well passively mode-locked solid-state lasers.

Continuous wave operation of a vertical transition quantum cascade laser above T=80 K

Abstract: Continuous wave operation of a quantum cascade laser at λ=4.6 μm is reported above liquid nitrogen temperature. Optical powers of 15 mW at 50 K and 2 mW at 85 K are reported. The single mode spectrum is temperature tunable over 1.8 cm −1. These devices also operated in pulse mode with 20 mW peak power at 200 K. Gain measurements show evidence for ultralow linewidth enhancement factor α<0.1.

Modeling of strained quantum-well lasers with spin-orbit coupling

Abstract: A complete model with the spin-orbit coupling for strained quantum-well lasers is presented. Explicit formulas for the momentum-matrix elements are given. The improvement in the threshold current density of tensile strained quantum-well lasers, as compared with that of the unstrained quantum well, is shown to result from the enhanced momentum matrix. The differential gain and the linewidth enhancement factor are calculated. The theoretical results show a smaller linewidth enhancement factor for compressively and tensile strained quantum wells than that of the unstrained structure, as has been experimentally observed. The temperature behavior of both the radiative component and the Anger component of the threshold current density is shown. Due to a decrease of gain and differential gain with increasing temperature, the threshold carrier density in unstrained quantum wells is increased with a large increment of the Auger recombination current at high temperature. For strained quantum wells, this increment is moderate because of the smaller threshold carrier density. >

Quantum cascade laser with plasmon‐enhanced waveguide operating at 8.4 μm wavelength

Abstract: A unipolar cascade laser operating at 8.4 μm wavelength is reported. The structure, grown by molecular beam epitaxy in the AlInAs/GaInAs material system, contains a 25‐stage coupled‐quantum‐well active region. The waveguide design is optimized to enhance optical confinement and reduce losses associated with the interface plasmon mode, by taking advantage of the dispersion of the refractive index of the contact layer near the plasma frequency. The peak optical power is 30 mW and the threshold current density 2.8 kA/cm2, at a heat‐sink temperature of 100 K and the highest operating temperature is 130 K. The slope efficiency at 100 K is ∼0.1 W/A, corresponding to a differential quantum efficiency of 5.4% per stage. This work, combined with previous results on shorter wavelength quantum cascade lasers, demonstrates that the wavelength of these new light sources can be tailored over a wide range by changing the active layers’ thicknesses using the same materials.

Electron relaxation times due to the deformation-potential interaction of electrons with confined acoustic phonons in a free-standing quantum well

Abstract: The confined acoustic phonons in free-standing quantum wells are considered in detail. The Hamiltonian describing interactions of the confined acoustic phonons with electrons in the approximation of the deformation potential and the corresponding electron transition probability density are derived. They are used to analyze the electron scattering times (inverse scattering rate, momentum relaxation time, and the energy relaxation time) in the test-particle approximation as well as in the kinetic approximation. It is shown that the first dilatational mode makes the main contribution to electron scattering in the lowest electron subband. The contribution of the zeroth mode and the second mode are also essential while the modes of higher order are insignificant. Our analysis is performed for both nondegenerate and degenerate electron gases. It is shown that electron scattering by confined acoustic phonons interacting through the deformation potential is substantially suppressed up to the electron energies corresponding to the energy of the first dilatational mode.

Electronic states in gallium arsenide quantum wells probed by optically pumped NMR.

Abstract: An optical pumping technique was used to enhance and localize nuclear magnetic resonance (NMR) signals from an n-doped GaAs/Al0.1Ga0.9As multiple quantum well structure, permitting direct radio-frequency measurements of gallium-71 NMR spectra and nuclear spin-lattice relaxation rates (1/T1) as functions of temperature (1.6 K < T < 4.2 K) and the Landau level filling factor (0.66 < v < 1.76). The measurements reveal effects of electron-electron interactions on the energy levels and spin states of the two-dimensional electron system confined in the GaAs wells. Minima in 1/T1 at v approximately 1 and v approximately 2/3 indicate energy gaps for electronic excitations in both integer and fractional quantum Hall states. Rapid, temperature-independent relaxation at intermediate v values indicates a manifold of low-lying electronic states with mixed spin polarizations.

Semiconductor laser element

Abstract: PURPOSE:To improve the high output and low noise characteristic by constructing an active layer of a single quantum well layer and superlattice multiple quantum well layers provided on the upper and lower surfaces thereof and forming a ridged waveguide structure for obtaining a self-oscillating laser element. CONSTITUTION:An active layer is constructed of a single quantum well layer 5 and superlattice multiple quantum well layers 4, 6 provided on the upper and lower surfaces thereof, and composition, film thickness, and impurity concentration of respective layers 4, 5, 6 are caused by have predetermined values. A light waveguide layer, on the opposite side of a semiconductor substrate with respect to the active layer, has a mesa-stripe-like ridged part extending in the resonator length direction, and light absorption and current constriction parts are formed on the light waveguide layer with the ridge part at the both ends of the ridged part, and self-oscillation is effected. Therefore, the laser light distribution is controlled and the light absorption layer is provided at a predetermined position relative to the active layer, so that the effective refraction index difference in the lateral direction of the active layer can be caused to have a desired value. Thus, a high output characteristic required by a writing and erasing light source for an optical disk, and a low noise characteristic required by a reading light source can be obtained.

Lasing at three-dimensionally quantum-confined sublevel of self-organized In/sub 0.5/Ga/sub 0.5/As quantum dots by current injection

Abstract: A laser oscillation from self-organized In/sub 0.5/Ga/sub 0.5/As quantum dots is achieved at 80 K by current injection. Lasing at a three-dimensionally quantum confined sublevel of the In/sub 0.5/Ga/sub 0.5/As quantum dots is clearly demonstrated for the first time by electroluminescence and diamagnetic energy shift measurement. The results predict the possibility of ultra-low threshold current operation of quantum dot lasers.

Tunable lasers handbook

Abstract: F. J. Duarte, Introduction: Tunable Laser Complementarity. Goal of This Book. F. J. Duarte, Narrow-Linewidth Oscillators and Intracavity Dispersion: Dispersive Oscillator Configurations. Physical Dimensions. Generalized Interference Equation. Dispersion Linewidth Equation. Beam Divergence. Intracavity Dispersion. Intracavity Multiple-Prism Dispersion and Pulse Compression. Transmission Efficiency of Multiple-Prism Arrays. Wavelength Tuning. Appendix: Dispersion of Multiple-Prism Arrays and 4 x 4 Transfer Matrices. R. C. Sze and D.G. Harris, Tunable Excimer Lasers: Excimer Active Media. Tuning of Discharge and Electron Beam Pumped Excimer Lasers. Discharge Excimer Lasers. Charles Freed,CO2 Isotope Lasers and Their Applications in Tunable Laser Spectroscopy: Vibrational Energy-Level Structive of the CO2 Molecule. Rotational Energy-Level Substructure of the CO2 Molecule. Processes Governing the Excitation of Regular BandLaser Transitions in CO2. Additional Characteristics of Regular Band CO2 Lasers Transitions. Lineshape Functions and Broadening Due to Gas Pressure and Doppler Shift in CO2 Gas. Spectral Purity and Short-Term Stability. Long-Term Line-Center Stabilization of CO2 Lasers. Absolute Frequencies of Regular Band Lasing Transitions in Nine CO2 Isotopic Species. Pressure Shifts in Line-Center-Stabilized CO2 Lasers. Small-Signal Gain and Saturation Intensity of Regular Band Lasing Transitions in Sealed-off CO2 Isotope Lasers. Laser Design. Spanning the Frequency Range between Line-Center Stabilized CO2 Laser Transitions. Spectroscopic Use of CO2 Lasers outside Their Fundamental 8.9- to 12.4-(m Wavelength Range. F. J. Duarte, Dye Lasers: Laser-Pumped Pulsed Dye Lasers. Flashlamp-Pumped Dye Lasers. cw Laser-Pumped Dye Lasers. Appendix of Laser Dyes. Norman P. Barnes, Transition Metal Solid-State Lasers: Transition Metal and Lanthanide Series Lasers. Physics of Transition Metal Lasers. Cr:AlO3. Cr:BeAl2O3 Ti:Al2O3. Cr:LiCaAIF6 and Cr:LiSrAlF6. Cr:GSGG, Cr:YSAG, and Cr:GSAG. Co:MgF2, Ni:MgF2, and V:MgF2. Wavelength Control Methods. Norman P. Barnes, Optical Parametric Oscillators: Parametric Interactions. Parametric Oscillation. Spectral bandwidth and Acceptance Angles. Birefringence Effects. Average Power Limitations. Nonlinear Crystals. Phase-Matching Calculations. Performance. Tuning. Paul Zorabedian, Tunable External-Cavity Semiconductor Lasers: Semiconductor Optical Gain Media. Classes of External-Cavity Lasers. First-Order Properties. Feedback Model. External-Cavity Design. Cavity Components. Survey of External-Cavity laser Designs. Mode Selectivity of Grating Cavities. Phase-Continuous Tuning. Characterization Methods for External-Cavity Lasers. Measurement of Facet and External-Cavity Reflectances. Multimode Suppression. Multiple-Wavelength Operation. Wavelength Stabilization. Advanced Modeling Topics. Construction and Packaging. Applications. Stephen Vincent Benson, Tunable Free-Electron Lasers: Methods of Wavelength Tuning. Broadly Tunable Optical Cavities. Wiggler Considerations. Tunable Laser Facilities and Their Characteristics. Summary. References. Subject Index. F. J. Duarte, Introduction. F. J. Duarte, Narrow-Linewidth Oscillators and Intracavity Dispersion. R. C. Sze and D.G. Harris, Tunable Excimer Lasers. Charles Freed, CO2 Isotope Lasers and Their Applications in Tunable Laser Spectroscopy. F. J. Duarte, Dye Lasers. Norman P. Barnes, Transition Metal Solid-State Lasers. Norman P. Barnes, Optical Parametric Oscillators. Paul Zorabedian, Tunable External-Cavity Semiconductor Lasers. Stephen Vincent Benson, Tunable Free-Electron Lasers. References. Subject Index.

Luminescence from excited states in strain-induced In_(x)Ga_(1-x)As quantum dots

Abstract: We have fabricated quantum dots by locally straining ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As quantum wells with self-organized growth of nanometer-scale InP stressors on the sample surface. The structure is completed in a single growth run using metalorganic vapor-phase epitaxy. Photoluminescence from the dots is redshifted by up to 105 meV from the quantum-well peak due to the lateral confinement of excitons. Clearly resolved luminescence peaks from three excited states separated by 16--20 meV are observed when the quantum well is placed at the depth of 1--10 nm from the surface of the sample. The observed redshift and peak separation are in agreement with simple calculations using a finite-element method and two-dimensional parabolic potential model. This structure is easily fabricated and offers a great potential for the optical study of relaxation and recombination phenomena.

Ideal theory of quantum well solar cells

Abstract: An ideal model for quantum well solar cells is developed and is used to theoretically explore the dependence of terminal characteristics on the host cell and quantum well properties. The model, which explicitly treats carrier generation and recombination in the quantum wells, is described and compared with an analogous ideal model for bulk homojunction cells. Open‐circuit voltages, short‐circuit current densities, and conversion efficiencies are then calculated as functions of the well and barrier band gaps for ideal cells in the radiative limit, assuming air‐mass‐zero (AM0) solar illumination at a cell temperature of 300 K. Qualitative trends in these characteristics and regimes of operation are identified, the effects of non‐radiative recombination are explored, and idealized approximations used in the model are assessed. Finally, published experimental data for quantum well solar cells are surveyed and discussed, and are found to exhibit strong qualitative consistencies with predictions from the ideal ...

Cavity characteristics of selectively oxidized vertical‐cavity lasers

Abstract: We show that a buried oxide layer forming a current aperture in an all epitaxial vertical‐cavity surface emitting laser has a profound influence on the optical and electrical characteristics of the device. The lateral index variation formed around the oxide current aperture leads to a shift in the cavity resonance wavelength. The resonance wavelength under the oxide layer can thus be manipulated, independent of the as‐grown cavity resonance, by adjusting the oxide layer thickness and its placement relative to the active region. In addition, the electrical confinement afforded by the oxide layer enables record low threshold current densities and threshold voltages in these lasers.