bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Expected Characteristics of 1.3μm GaInNAs/GaAs Vertical Cavity Surface Emitting Lasers
Authors: Miyamoto T. , Takada T. , Takeuchi K. , Koyama F. , Iga K.
Published: February 2023

The long wavelength vertical cavity surface emitting laser (VCSEL) is becoming one of key devices for future optical communication and interconnection systems. Room temperature (RT) continuous-wave (CW) operations were demonstrated for long wavelength VCSELs with a reduced threshold current and an increased operating temperature [1, 2]. However, temperature characteristics such as characteristic temperature T0 and the maximum operating temperature are not sufficient for use in actual systems. These are due to carrier leakage related to the small conduction-band discontinuity of GaInAsP/InP systems, difficulties in fabrication of small current confining structures and high reflective mirrors, a large non-radiative absorption, and so on. Recently, the GaInNAs material was proposed as a new long wavelength system emitting 1.3μm and 1.55μm grown on GaAs substrates [3] and 1.2μm RT-CW operations of edge emitting lasers have been demonstrated [4]. The bandgap bowing between arsenide and nitride system is very large and thus long wavelength emission and large conduction-band offset are expected for this material system.
Quantum Statistical Effects of Microcavity Exciton Polaritons
Authors: Cao H. , Pau S. , Tassone F. , Huang R. , Björk G. , Yamamoto Y.
Published: February 2023

In the past few years there has been extensive study on exciton-photon coupling in a quantum well (QW) embedded semiconductor microcavity [1, 2]. The strong coupling between the QW exciton state and the cavity photon state results in the new eigenstates of this coupled systems, i. e. the exciton-polariton states [3]. The microcavity exciton-polaritons, as new quasi particles, features interesting quantum statistics.
Anomalous Diffusion of Repulsive Bosons in a Two-Dimensional Random Potential
Authors: Fukuzawa T. , Kim S. Y. , Gustafson T. K. , Haller E. E. , Yamada E.
Published: February 2023

Two-dimensional (2D) bosons can undergo a Kosterlitz-Thouless transition[1], which does not involve macroscopic occupation of a single quantum state, but which can still result in superfluidity. In addition, strongly interacting bosons subject to a random potential can also exhibit superfluidity, as in the case of charged superfluidity that occurs in high-T
c
superconductors. Competition between the strength of the interaction and the degree of potential disorder are among the many complicated and competing factors which determine whether superfluidity is promoted or supressed in a Bose system[2]. Strong potential disorder forces bosons to localize and can result in an insulating Bose glass phase. Alternatively, repulsive interactions among bosons act to release them from their traps, to keep their inter-particle distances as uniform as the potential allows, and to arrange the flow direction. An appropriate interaction strength can thus promote superfluidity.
Quantum Mode Correlations in Vertical Cavity Surface Emitting Lasers
Authors: Kilper D. C. , Roos P. A. , Carlsten J. L. , Lear K. L.
Published: February 2023

Considerable progress has been made during the past decade in understanding the quantum noise processes associated with the generation of photon-number squeezed light from conventional semiconductor lasers. Microcavity lasers, such as the vertical cavity surface emitting laser (VCSEL), have also been predicted to generate photon-number squeezed light based upon the high impedance pump noise suppression model1. Previous measurements, however, have only shown noise far above shot noise2. Several features of VCSELs are expected to lead to important differences from the quantum photon statistics in conventional edge-emitters. Because the cavity length is matched to the lasing wavelength, only a single longitudinal mode is present. This eliminates noise contributions from longitudinal mode competition noise. However, VCSELs often oscillate in multiple transverse modes, particularly for high efficiency devices operating at high pump rates, necessary for squeezing. Although quantum mode correlation effects between multiple longitudinal modes have been studied extensively in edge-emitting devices3, quantum correlations between different transverse modes have not been observed. Furthermore, because of the high mirror reflectivities (>99%) squeezed output from a VCSEL can provide confirmation of the high impedance pump noise suppression model predictions in the good cavity limit, for which the theory was formulated. The enhanced spontaneous emission into the lasing mode that is characteristic of these devices can potentially lead to squeezed output at all pump rates. In present devices, the microcavity effects contribute to a low threshold current that allows for the high pump rates necessary for squeezed output to be achieved at room temperature without damage to the laser.
Time Resolved Amplitude and Phase of Coherent Four Wave Mixing Emission from GaAs Quantum Wells
Authors: Walecki Wojciech J. , Fittinghoff David N. , Smirl Arthur L.
Published: February 2023

Time integrated and time-resolved four wave mixing (FWM) techniques using ultrashort pulses have proven to be extremely powerful tools for studying coherent processes and excitonic effects in semiconductors and semiconductor multiple quantum wells (MQWs). These techniques have provided considerable information about the time dependent amplitude of the emitted FWM signal, but they provide no information about the time dependent phase. Complete characterization of the emitted electromagnetic field requires the measurement of both amplitude and phase. Moreover, it has been emphatically demonstrated1 that the phase dynamics carry essential information about the optical interactions and the fundamental processes. Consequently, failure to measure the phase will result in a loss of this information.
Probing radial electron-hole wavepacket dynamics in quantum wells with terahertz pulses
Authors: Maslov A. , Citrin D. S.
Published: February 2023

The routine availability of sub-ps laser pulses has led to the preparation and probing of electronic wavepackets in Rydberg atoms. [1] An atom – initially in the ground state – is excited optically by a short pulse to a superposition of states centered at a large principle quantum number n. Both radially [2] and angularly localized [3] electronic wavepackets have been created. The wavepacket at various time delays may then be probed by field ionization using a pulsed electric field. [2-4] In semiconductor quantum wells (QW) optically excited electron-hole (e-h) wavepackets have also been observed; [5,6] however, such wavepackets differ markedly from their Rydberg-atom counterparts. In the QW, an optical pulse centered near the QW bandedge E0 and with a bandwidth that exceeds the 1s-exciton binding energy coherently excites from the crystal ground state excitons with principle quantum numbers ranging from n = 1 through the continuum. Moreover, the dipole selection rule for the excitation of e-h pairs from the crystal ground state dictates that only s states are created since these are the only states with nonzero e-h overlap. In Ref. [5], two-pulse four-wave mixing (FWM) experiments were performed on compressively strained Ino.o8Gao.92As/GaAs multiple QW’s excited by 110-fs optical pulses. Compressive strain in such structures substantially increases the light-hole-heavy-hole splitting, thus allowing the excitation of e-h pairs involving only the heavy-hole. The time-integrated (TI-) FWM signal as a function of time delay between the two pulses shows distinct beating when the laser center frequency is near resonance with E0.
Monte Carlo Simulation of Femtosecond Spectroscopy in Semiconductor Heterostructures
Authors: Goodnick Stephen M.
Published: February 2023

Recently, Knox and coworkers1-3 have used time resolved absorption spectroscopy to study the relaxation kinetics of optically excited carriers in undoped1, n and p modulation doped quantum wells2,3. In these experiments, carriers were photoexcited using a 50fs pump pulse which generated electrons with an excess energy of approximately 20meV. Relaxation from the athermal photoexcited distribution to a relaxed equilibrium distribution was observed in the differential absorption with the characteristic relaxation times less than 200fs depending on the concentration and carrier type(n or p). Since the excess carrier energy is less than the optical phonon energy, relaxation in these experiments was argued to arise from carrier-carrier interaction.
Optical Nonlinearities and Cross-Well Transport In Multiple Quantum Well Structures
Authors: Miller A. , Manning R. J. , Bradley P. J.
Published: February 2023

Multiple quantum well (MQW) semiconductors provide a number of nonlinear optical effects associated with well resolved, room temperature, exciton absorption features. Refractive nonlinearities arising from the saturation of the exciton by phase space filling, and the electric field induced quantum confined Stark effect (QCSE) can both be used to produce nonlinear characteristics at low laser powers. We use these effects to monitor optically created excess carrier dynamics in GaAs/AlGaAs MQW structures at room temperature on picosecond timescales. In particular, we have determined the time constants relating to cross-well carrier diffusion by thermionic emission from quantum wells, and tunnelling through 60Å barriers in the presence of an electrical field. Measurement of the temperature dependence of four wave mixing decay rates allows a study of the thermionic emission process, while the voltage dependence of the build up time of the cross­well photocurrent establishes the latter. The differential emission rates for both processes will be discussed.
Free Carrier Radiative Recombination in 2D: PbTe Quantum Wells
Authors: Heyen E.T. , Hagerott M. , Nurmikko A.V. , Partin D.L.
Published: February 2023

There have been a number of studies aimed at isolating radiative recombination in semiconductor quantum wells, a process which in many instances is strongly influenced by excitonic effects such as in III-V (e.g. GaAs [1]) or wide-gap II-VI (e.g. ZnSe [2]) semiconductor heterostructures. Recently, Matsusue and Sakaki have exploited modulation doped GaAs/(Ga,Al)As multiple quantum wells (MQW) to show how radiative recombination of a quasi-two dimensional (2D) free electron-hole gas can be distinctly identified while reducing excitonic complications [3]. In narrow-gap semiconductors, such as PbTe, excitonic effects are negligible; therefore quantum wells from these materials offer a clear opportunity to study quasi-2D free carrier radiative recombination over a wide temperature and density. We show here that radiative recombination dominates in high quality MBE-grown PbTe/(Pb,Eu)Te MQW’s. At the same time PbTe/(Pb,Eu)Te based heterostructures show excellent prospects as low threshold diode injection lasers at mid-infrared wavelengths [4].
Room Temperature Confinement and Photoluminescence in HgCdTe Multiple Quantum Wells
Authors: Cesar C.L. , Islam M.N. , Feldman R.D. , Spitzer R. , Austin R.F. , DiGiovanni A.E. , Shah J. , Orenstein J.
Published: February 2023

We have grown HgCdTe/CdTe Multiple Quantum Wells (MQW) with the lowest transition near 3 µm, and we have observed room temperature confinement and photoluminescence. HgCdTe/CdTe MOW’S of different compositions can be used over the entire infrared range, since the material is lattice matched from 0 to 1.5 eV. The importance of the 3 µm region comes from the possibility of a communications system operating with fluoride fibers. The MQW was grown by MBE with 50 periods of 100 A of Hg0.15Cd0.85Te barriers and 50 A of Hg0.73Cd0.27Te wells (1). Transmission Electron Microscopy (TEM) and X-ray data confirm very little interdiffusion and high reproducibility of layer thickness. The thick barriers are necessary for strong confinement, especially for the light hole. Therefore we can see the heavy and light hole to conduction band transitions. The separation between these two transitions is mainly determined by the value of the valence band offset (VBO) between HgTe/CdTe, a controversial parameter with reported values ranging from 40 to 400 meV (2), and suggestions of being temperature dependent. Our data support a value near 400 mev which has little or no temperature dependence.
Second-order intersubband nonlinear optical susceptibilities of asymmetric quantum well structures.
Authors: Khurgin J.
Published: February 2023

Nonlinear optical properties of quantum wells (QW’s) and superlattices (SL’s) have recently become an object of intense studies 1,2. Quantum confinement of carriers leads to existence of strong resonances in the absorption spectra attributed to both conduction-to-valence band 3 and intersubband 4 transition. That, in turn, leads to large optical nonlinearities. Third order nonlinearity in symmetrical QW’s and SL’s have been studied by numerous authors 5-8. More recently, calculations of second order nonlinear coefficients of asymmetric QW structures were made for interband 9,10 and intersubband 10,11 transitions. Second -order nonlinear properties based on interband processes in various asymmetric QW structures were evaluated in Ref 10 for wide range of materials and QW geometries. It was snown that although both second harmonic generation (SHG) and linear electro-optic (LEO) coefficient are large (on the order of 10−10m /V) they are at least an order of magnitude smaller than what could be expected from a two-level asymmetric system with comparable transition strength. The reason for that is compensation of second-order susceptibilities associated with various ground and excited states and having opposite signs.
Enhanced Spontaneous Emission from GaAs Quantum Wells with Monolithic Optical Microcavities
Authors: Yokoyama H. , Nishi K. , Anan T. , Yamada H.
Published: February 2023

To date, several experiments have demonstrated the alteration of materials’ spontaneous emission rate in cavities1-3). Altering the spontaneous emission is also interesting from the device point of view. For example, Kobayashi et al. proposed the concept of a thresholdless laser with the full confinement of spontaneously emitted photons in closed microcavities4).
1×16 Arrays of GaAs/AlGaAs Multiple Quantum Well Optical Modulators with 26:1 Contrast
Authors: Bailey R.B. , Sahai R. , Lastufka C.
Published: February 2023

Optical modulators fabricated from GaAs/AIGaAs multiple quantum well (MQW) structures have been operated in transmission,1 reflection,2 waveguide,3 and Fabry-Perot resonator4 modes with maximum contrast ratios ranging from 5 to 10. Small arrays of these devices have also been reported,5 but with lower contrasts and relatively little data on uniformity. Large arrays with high contrast and uniformity are required in optical computing and signal processing applications. In this work we report the fabrication of 16 x 16 arrays of transmission and reflection modulators with a maximum contrast ratio of 26. This is believed to be the largest room temperature contrast ever achieved in a MQW device. We have also made measurements of the uniformity of 1x16 columns of modulators from these arrays and have demonstrated that device-to-device variations in the transmission arrays are approximately 1% of the average transmission.
Theoretical optimisation of Electrooptical Phase Modulation in InGaAsP Quantumwells.
Authors: Botteldooren D. , Baets R.
Published: February 2023

The superior performance of light modulators based on the quantum confined Stark effect has been accepted for some time. Many experimental and theoretical data were obtained for GaAs-AlGaAs QW and SL. In the 1.55μm optical window, which is of particular interest for optical communication purposes, InGaAs and InGaAsP QW give better performances. For the ternary material refractive index data were published1 and the use of InGaAs and InGaAsP QW's in waveguide modulators2 and DBR lasers3 was demonstrated. Recently the advantage of using quaternary quantum wells for electrooptic phase modulation at 1.55μm was stressed4. The main point of interest is the additional degree of freedom, namely the InGaAsP composition. The problem of finding the optimal composition together with the best possible QW size for maximal phase modulation, within certain restrictions for the applied field, is treated on a theoretical basis in this paper. The modeling of the electric field dependent absorption in QW’s has already obtained a lot of attention5. Refractive index changes under applied field are much more difficult to model accurately due to the long energy range of the changes induced by the field. Recently Yamamoto et al.6 presented some theoretical results in a 30nm InGaAsP QW. They neglect exciton effects and only consider contributions of heavy holes. Both approximations work quite well in the large well limit, but are less accurate for smaller QW's.
Nonlinear Optical Properties of Quantum-Confined CdSe Microcrystallites
Authors: Morgan R.A. , Park S.H. , Koch S.W. , Peyghambarian N. , Hall D.W. , Borrelli N.F.
Published: February 2023

Lately, quantum confinement effects in semiconductor microstructures have been studied because of their interesting physics and possible nonlinear optical device applications.1-2 The basic optical properties of quantum dots (QDs), which exhibit 3D-confinement effects, have recently been discussed theoretically.1 In this paper, we report a comprehensive experimental study of the steady-state nonlinear optical properties of specially-prepared quantum-confined CdSe microcrystallites suspended in a transparent borosilicate glass matrix.2 Three samples were investigated. The average crystallite diameters of these samples were measured using transmission electron microscopy to be 30 Å, 44 Å, and 79 Å, respectively.2 For bulk CdSe, the exciton Bohr radius (aex) is ≅ 56 Å therefore, our samples fall within the so-called intermediate confinement regime (ah< R <ae).1-2
Disorder of a GaAs-AlGaAs Quantum Well as a Technique For Fabricating Quantum Wires
Authors: Zarem H. A. , Sercel P. C. , Hoenk M. E. , Yariv A. , Vahala K. J.
Published: February 2023

Submicron bandgap tailoring of semiconductors has many exciting applications such as optical waveguiding and carrier confinement. When the carriers are confined to dimensions comparable to their deBroglie wavelength, they exhibit quantum size effects [1,2,3]. Techniques such as molecular beam epitaxy of GaAs-AlGaAs structures allow for such tailoring in one dimension, but control in the other two dimensions requires other techniques. Most of the work toward lateral confinement of carriers to these dimensions has focused on etching techniques [1,3] due to the lack of other methods for creating such small structures. For most device applications, however, a lateral confining structure which does not create an exposed surface is essential. One such technique is the use of ion implantation to selectively disorder a quantum well [2].
Direct Experimental Comparison of GaAs-AlGaAs Multi-Quantum Well Modulators Grown on GaAs and Silicon Substrates
Authors: Goossen K.W. , Boyd G.D. , Cunningham J.E. , Jan W.Y. , Miller DAB. , Chemla D.S. , Lum R.M.
Published: February 2023

Recently there has been a maturing of the technology of GaAs/AlGaAs multiple quantum well (MQW) p -i (MQW)-n modulators1-4 and related self electro-optic effect (SEED) devices 5-7 grown on GaAs substrates by molecular beam epitaxy (MBE). It has been demonstrated that these devices can operate at several GHz8, and that with the incorporation of an MBE-grown dielectric mirror beneath the modulator they may operate in reflection mode.4 These properties make MQW modulators attractive as a device for communicating off chip via optical signals. Since the majority of electronic devices are silicon, it is important to determine the quality of GaAs MQW modulators grown on Si substrates.
Integrated Multiple Quantum Well Lasers and Optical Amplifiers at 1.55 Micron Wavelength
Authors: Koren U. , Eisenstein G. , Tucker R.S. , Koch T.L. , Miller B.I.
Published: February 2023

Photonic integrated circuits (PIC's) can be composed of many active waveguide elements such as lasers, detectors, optical modulators and switches, optical amplifiers etc. These elements can be optically coupled via a complex branching network of low loss passive waveguides all on the same semiconductor chip. Some of the more obvious advantages of this technology are the compact, stable and efficient couplings that can be obtained between the various optical elements of the PIC, and also the potential extensive use of optical amplifiers inside the PIC to compensate for undesirable optical losses that may occur inside the optical circuit or at the outside world. It is possible to use optical amplifiers as switching elements in combination with optical power combiners or splitters in a complex waveguide optical switching circuits. This opens the possibility of creating switching PIC's with switching speeds higher than 1 GHz and with inherent optical gain available in the actual switches.
Carrier-Density- and Excitation-Energy-Dependent Γ-X Photoluminescence of Type-II GaAs/AlAs Superlattices
Authors: Olbright G. R. , Owyoung A. , Hjalmarson H. P. , Brennan T. M.
Published: February 2023

Recently, "Type-II" semiconductor superlattices characterized by a "staggered" alignment of the valence and conduction bands have attracted much interest.1-5 Considerable effort has been directed toward understanding the optical properties of these structures. We focus our attention on a subclass of GaAs/AlAs superlattices in which quantum size effects produce the staggered Type-II band structure as illustrated in Figure 1. Although the linear optical spectroscopy of these structures is fairly well understood, to date there is a paucity of research on their nonlinear optical properties and inter-subband and inter-layer relaxation dynamics.
Excitonic Behavior in Pseudomorphic InGaAs/(Al)GaAs Quantum Wells Grown by Mbe
Authors: Ackley D.E. , Colvard C. , Lee H. , Nouri N.
Published: February 2023

Pseudomorphic InGaAs quantum well (QW) structures have been the subject of considerable interest for electronic and optoelectronic devices. In order to optimize pseudomorphic QW structures for advanced devices it is necessary to understand the properties of the interfaces with the barrier layers. To this end we have utilized photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy to investigate the optical properties of InGaAs strained single quantum wells (QWs) grown by molecular beam epitaxy with different barrier layers. Samples with 100A In.15Ga.85As layers bounded on top and bottom by either GaAs or Al.15Ga.85As were studied over the temperature range 2-300 K. All four possible barrier combinations were included. The GaAs/InGaAs/GaAs samples exhibited linewidths as small as 1.3 meV at 2 K, which are the narrowest yet observed for these structures grown by conventional techniques. Similar results were observed at 2 K for QWs with AlGaAs barriers below, but the linewidths of samples with AlGaAs on top were substantially broadened. Measurements of the excitation spectra of these samples showed a substantial free exciton component to the luminescence from samples without top AlGaAs barriers. Samples with top AlGaAs barriers, however, showed little free exciton contribution. Investigation of the temperature behavior of the luminescence suggest that the homogeneous broadening in all the samples is similar, but that the inhomogeneous contributions are different for the various structures. In addition, the temperature dependent measurements showed an additional bound exciton component of the samples with top barriers that was ionized at temperatures above 15 K. Samples with lower AlGaAs barriers showed an anomalous increase in linewidth with increasing temperature which is still under investigation.
Hole eigenenergies in GaAsP/AlGaAs single quantum wells with biaxial tensile strain
Authors: Bertolet Daniel C. , Hsu Jung-Kuei , Lau Kei May
Published: February 2023

The effects of biaxial strain on the band-structure of III-V semiconductors have been investigated theoretically1,2 and experimentally3. These effects offer new degrees of freedom for heterostructure design, so-called "band-structure engineering4." In particular, when III-V semiconductors are biaxially strained, the heavy- and light-hole bands become non-degenerate, and anisotropic. The valence-band configuration that arises from biaxial tensile strain is particularly well-suited for devices that involve optical absorption. Tensile strain and the quantum size effect (QSE) of a square potential well have the opposite effect on hole energy at k=0, and if the appropriate material parameters and structural dimensions are chosen, the heavy and light-hole eigenenergies of the QW will coincide. Equivalent heavy- and light-hole excitonic resonances will result in a larger absorption coefficient5, which can improve the performance of photodiodes and high speed optical modulators6. In addition, the capability to tailor the relative energies of the heavy- and light-hole could lead to new devices that exploit the different polarization-selection rules for the heavy- and light-hole excitonic transitions6,7. In this presentation we report on the growth and photoluminescence of strained GaAsP/ALGaAs single QW′S. The combined effects of biaxial tensile strain and QSE on the hole eigenenergies will be clearly demonstrated.
Strained Layer InGaAs GRIN-SCH Lasers Grown by MBE
Authors: Ebner J. T. , Plant T. K. , Arthur J. R.
Published: February 2023

The use of ternary In compounds in the active region of a diode laser allows devices to be constructed which operate at wavelengths longer than that obtainable from binary GaAs. If these In compounds are included in a structure grown on a GaAs substrate then they need to be kept thin enough (pseudomorphic) to avoid misfit dislocations which adversely affect device performance. A few lasing devices using pseudomorphic InGaAs have been reported previously (1,2) without comparison to the equivalent structure with no pseudomorphic layer. In this work two laser diode structures are compared: one containing strained InGaAs and the other identical in all respects except with unstrained GaAs in place of the strained InGaAs.
High Quality Quantum Wells of InGaP/GaAs Grown by Molecular Beam Epitaxy
Authors: Quigley J. H. , Lee H. Y. , Crook M. D. , Hafich M. J. , Robinson G. Y. , Li Du , Otsuka N.
Published: February 2023

The materials system AlGaAs/GaAs has been used extensively for synthesis of quantum well (QW) optoelectronic devices. The III-V alloy InGaP provides an alternative to AlGaAs for confinement of GaAs QWs. At the composition for lattice matching to GaAs, In0.48Ga0.52P exhibits a room temperature bandgap of 1.89 eV, somewhat larger than that of Al0.3Ga0.7As, and the In0.48Ga0.52P/GaAs valence band offset (ΔEv) is about 0.3 eV, larger than that of the Al0.3Ga0.52As/GaAs heterojunction. Furthermore, InGaP exhibits a lower concentration of deep levels than AlGaAs, and InGaP does not oxidize as readily as AlGaAs. InGaP/GaAs QWs have been previously reported by Razeghi et al., who used metalorganic chemical vapor deposition to grow wells as narrow as 15Å(1) We report here the growth of InGaP/GaAs QWs by gas-source molecular beam epitaxy (GSMBE). Single QWs as narrow as 6Å and multiple QW superlattices with abrupt interfaces are described.
Optical Transitions in Strained Layer InxGa1−xAs/InP Quantum Wells
Authors: Gershoni D. , Temkin H. , Panish M. B.
Published: February 2023

We present a study of the optical transitions between confined particle states of strained layer quantum wells (SLQWs). SLQWs of InxGa1−xAs/InP with x ranging from 0 to 1 are an excellent system for this type of study because their strain varies systematically from −3.8%(x = 0) to +3.2%(x = 1). In previous studies we have used electro-optic techniques [1,2] and admittance spectroscopy [3] to show that most of the change with x in the band gap discontinuity between InP and InxGa1−xAs layers, takes place in the conduction band. A simple phenomenological deformation potential model, has enabled us to successfully calculate the lowest ( n = 1 ) excitonic transitions for any x and in particular to explain a type I to type II superlattice transition for x ≅ 0.2. In this study we show that in order to account for higer order transitions one has to include non-linear terms in strain and band non-parabolicity effects. Our model which contains no adjustable parameters agrees well with the observed transitions.
A Strained Superlattice Buffer Layer for InGaAs/GaAs Quantum Wells
Authors: VanEck T. E. , Niki S. , Chu P. , Chang W. S. C. , Wieder H. H. , Mardinly A. J. , Aron K. , Hansen G. A.
Published: February 2023

Good electroabsorption has been demonstrated recently in InGaAs/GaAs quantum wells.1,2 A structure described previously1 had only ten quantum wells, and although InGaAs and GaAs are not lattice-matched, the total strain energy in this structure was small enough that the quantum wells grew pseudomorphically, i. e., the InGaAs was strained so that its in-plane lattice constant was equal to the lattice constant of the GaAs substrate. This structure showed good electroabsorption characteristics, but only 6% modulation depth. For a device with 50% modulation depth, about 100 quantum wells are required. However, structures containing only 20 quantum wells appeared to be non-pseudomorphic. Thus 100 quantum wells can not be grown pseudomorphic to the substrate, yet they must be grown with no dislocations to have good electroabsorption characteristics. This can be accomplished by growing the quantum well structure on top of a thick, uniform buffer layer with a lattice constant equal to the weighted average of the lattice constants of the quantum well and buffer layers. Lattice relaxation by means of dislocations occurs only in the buffer layer, and both quantum wells and barriers grow pseudomorphic to the buffer layer rather than the substrate.3 A similar result can be achieved by eliminating the buffer layer; the lattice relaxation occurs in the first few quantum wells, and the rest are dislocation-free.2,4,5 We have employed this method to produce a structure with 80 quantum wells which exhibits good electroabsorption characteristics. We have also grown 50 quantum wells on a strained superlattice buffer layer consisting of alternating layers of InGaAs and GaAs, each 20Å thick. The purpose of this is to remove the dislocations from the quantum wells, which are optically active, and place them in the inactive superlattice.
Orientation dependence of the aluminum concentration in AlxGa1−xAs epilayers grown by molecular beam epitaxy on a nonplanar substrate
Authors: Hoenk Michael E. , Chen Howard Z. , Yariv Amnon , Morkoç Hadis , Vahala Kerry J.
Published: February 2023

Advances in crystal growth technology have led to increased control of the crystal composition during the growth process. An example of this is the monolayer precision with which the composition of semiconductor crystals can be varied using molecular beam epitaxy (MBE). Since MBE growth on planar substrates affords control of the composition only along the growth axis, additional processing is required to introduce lateral variation of the crystal properties. The use of nonplanar substrates produces lateral variations in the properties of crystalline layers grown by MBE, adding a new dimension to the power of MBE as a tool for device fabrication.1–4 For example, growth on nonplanar substrates has been used for the fabrication of buried heterostructure quantum well lasers in a single growth step3, and it has been proposed as a technique for the fabrication of quantum wire lasers.3,4
Electro-Absorption and Refraction by Electron Transfer in Asymmetric Modulation-doped Multiple Quantum Well Structures.
Authors: Wegener M. , Bar-Joseph I. , Chang T.Y. , Kuo J.M. , Chemla D.S.
Published: February 2023

Remarkable changes in the absorption spectrum of n-type modulation doped quantum wells (QW) are produced by varying the electron concentration inside the QW in field effect structures1,2. In the vicinity of the gap, the dominant process is phase space filling. It results in a bleaching of the exciton resonances and a net blue shift of the absorption edge, similar to the Bumstein-Moss shift seen in bulk materials. So far the effect was only demonstrated on single QW, where the carriers were moved in the plan, in and out of the deplition region of a Schottky contact3,4. In this paper we present and demonstrate a novel concept of electric field driven electron transfer in and out of a multiple period QW structure by providing a reservoir of charges in close proximity to each QW. We report measurements of the differential absorption and the refraction associated with this electron transfer in a 10 Reservoir-QW period.
Inducing normally forbidden transitions within the conduction band of GaAs quantum wells
Authors: West Lawrence C. , Pan Janet L. , Walker Susan J. , Malik Roger J. , Walker John F.
Published: February 2023

Recently, a new type of intersubband transition in GaAs quantum wells was observed by West and Eglash [1,2]. This transition differed from previous intersubband transitions [3] in that it had a direct, fully allowed, dipole between the envelope wavefunctions rather than the Bloch wavefunctions, was spectrally narrow, and temperature stable. This particular type of intersubband transition was termed a quantum well envelope subband (or state) transition “QWEST.” The Stark energy shift between the first and second conduction subbands in a GaAs quantum well was observed by Harwit and Harris [4]. Infrared detectors utilizing the QWEST have also been made [5] recently.
Effects Of Modulation Doping On Intersubband Relaxation By Polar Optical Phonons In Multiple Quantum Well Structures
Authors: Educato J. L. , Sugg A. , Leburton J. P.
Published: February 2023

Recently, intersubband relaxation in modulation doped GaAs/Al
x
Ga
1−x
As multiple quantum well structures (MDMQWS) has been observed directly by an infrared bleaching technique [1,2]. The intersubband time constants determined experimentally are surprisingly long (≈ 10 ps). But, as well width increases, electron lifetimes decrease. A well width change from 47 Å to 59 Å results in approximately a factor of two decrease in relaxation time.
Tunneling Dynamics and Resonant Coupling of Electrons in GaAs/AlAs Coupled Double Quantum Well Structures under Electric Fields
Authors: Matsusue T. , Tsuchiya M. , Sakaki H.
Published: February 2023

Resonant tunneling(RT) phenomenon in double-barrier(DB) heterostructure[1,2] has a conceptual similarity to a transmission of optical waves in Fabry-Perot (FP) resonator and involves time delay. Its dynamics should be investigated since they limit the ultimate speed of RT devices. Such a study will also clarify similarities and differences between electronic and optical waves. In our previous work[3], we investigated the tunneling escape process of electrons from AlAs/GaAs/AlAs DBRT structures. The measured escape rate was well explained by the idealized theory of FP-like model, which predicts the tunneling escape time τ in DBRT structures is given by |t| 2vk/Lw, when |t|2 ≪1, where t is the transmission coefficient through the barrier, vk is the group velocity of electrons and Lw is the well width. This predicted escape time is equal to the one calculated by the sequential tunneling model, suggesting that the tunneling escape time is not strongly dependent on the coherency of electron waves. This simple relation may not hold for the tunneling process between quantum wells(QW), where resonant coupling effect plays a more sophisticated role. To clarify the resonant tunneling phenomena between QWs, we report, in this paper, our study on electron dynamics in several different double GaAs QW structures separated by thin AlAs barrier, where the coupling condition between QWs was varied by electric fields. Tunneling process was studied at ~20K by measuring time resolved photoluminescence(PL). Picosecond pulses of a mode-locked dye laser were used to generate electron hole pairs in QWs, and the subsequent PL from particular QWs was monitored by a streak camera to determine the time variation of electron density in the QWs. Note that the electrons are lost either by recombination (radiative[4] and nonradiative) and/or by tunneling process. Since the mass of heavy hole is quite heavy, hole tunneling can be neglected at least in the initial phase of tunneling.
Bidirectional Feedthrough Light Emitting Diode for Fiber Optic Communications
Authors: Simms Garfield , Hunsperger Robert , Whitehead T. Wilson
Published: February 2023

In fiber optic communication systems, emission and detection are usually handled by separate devices. However, previous research has shown that emission and detection can be embodied in a monolithic emitter-detector diode. In doing so, the number of components are reduced, which inherently makes the optical system less expensive and more reliable. By using the Franz-Keldysh shift it has been shown that detection can be accomplished at the band edge; however, the research thus far has been for end terminal devices. In this new research, we have created a broad area feedthrough structure which, when placed in an optical network, will act as a tri-state optical switch. This device when forward biased will emit an optical signal; when reverse biased it will detect that optical signal with a 0.1 A/W responsivity, and with a 0.1-0.4V pre-bias it becomes semi-transparent. The diodes have been optimized for a modulation frequency of less than 50MHz and a wavelength of 900nm. These diodes will have broad application in local area networks, in automobiles and intra-instrumentation links.
Upconversion and Energy Transfer in Active Media for Solid State Lasers
Authors: Yeh Donald C.
Published: February 2023

There is much interest in new solid-state laser materials, and materials which are codoped with two ions, one to absorb the pump radiation (donors) and the other to lase (acceptors), are of special importance. Energy transfer and frequency upconversion play important roles in these systems. Efficient upconversion has been observed in the fluoride glasses and crystals. For example, the 1.5-μm upconversion efficiency of the 4I11/2 emission from the fluoride glass with 4 mol % ErF3 is over 10% for an absorbed light intensity of 400 W/cm2. This high efficiency could play either a useful or a detrimental role for the formation of efficient laser systems. This paper reviews energy transfer and frequency upconversion processes in fluoride glasses.
The Absorption of Optical Radiation in the Atmosphere
Authors: Rothman Laurence S.
Published: February 2023

In this paper we discuss the basis for performing high resolution calculations of transmission and emission of radiation in the atmosphere. We restrict our comments to gaseous molecular absorption in the visible to millimeter region of the electromagnetic spectrum.
Elastic Backscatter Lidar Measurements of Aerosols and Clouds
Authors: Russell Philip B.
Published: February 2023

This paper briefly reviews current applications of the elastic backscatter lidar technique,1 with emphasis on aerosol and cloud measurements. For completeness, it also includes measurements of wind via aerosol pattern tracking, elastic backscatter measurements of molecular density and temperature, and high-spectral-resolution measurements of aerosol properties. These are all closely related techniques not covered by other papers at this conference.
Remote Sensing of Upper Atmospheric Winds
Authors: McCleese D. J. , Margolis J. S.
Published: February 2023

In this paper we describe a passive infrared sensor for remote sounding winds in the stratosphere and mesosphere. We will describe the measurement approach and instrument development work performed to date, including a laboratory demonstration of the instrument concept.
A Laser Weather Indicator System
Authors: Stone Richard J.
Published: February 2023

A second generation laser weather indicator (LWI) system has been developed by the Advanced Systems Laboratory, Systems Development Office (SDO), National Weather Service (NWS) to separate and quantify rain, snow and hail. The discussion of the system is derived from Acheson, 1982, and Abernathy, 1982. The presentation will concentrate on data analyses and algorithm development by the Test and Evaluation Division, (T&ED), NWS.
Inverse Methods for Remotely Determining the Absorption and Anisotropic Scattering Properties of Optically-Thick Atmospheres
Authors: McCormick N. J.
Published: February 2023

Three methods of using cw or pulsed electromagnetic sources to determine the coefficients of the Legendre expansion of the single-scattering phase function are compared.
Mie Scattering of Electromagnetic Waves by Precipitation
Authors: Jin Y. Q. , Kong J. A.
Published: February 2023

The theory for passive remote sensing from a layer of cloud or rain has been developed by using the Mie scattering phase functions [1,2]. Extending the theory to include active remote sensing, we employ all four Stokes parameters for the intensities and calculate for the bistatic scattering coefficients, backscattering cross sections, crosstalk, and brightness temperatures. The theoretical results are illustrated and compared with various experimental data [2-6]. The same techniques are applicable in the infrared range for scattering by aerosol particles.
Aspects of Specie and Temperature Retrieval From High Resolution Infrared Spectral Earthlimb Emission Data
Authors: Kumer J. B. , Uplinger W. G. , James T. C. , Newkirk L. L. , Roche A. E. , Goldman A. , Murcray D. , Harris Ron , Megill L. R.
Published: February 2023

The simulation of the data processing and analysis that is required to extract useful geophysical information from data obtained by a remote sounding experiment is useful in that (1) it provides an opportunity to test the retrieval algorithms under known conditions and (2) it can influence instrument design parameters. Examples of this kind of work would include an article by Chahine (1972) in which a general relaxation method for inverse solution of radiative transfer equations is described. This article describes the application of the method to a single species. Other recent examples would include papers by Majumdar et al (1981) and Abbas et al (1981) which describe the inversion of high resolution measurements of atmospheric absorption. These papers also consider application of the techniques described to single species and make use of simulated radiance data in order to compare the derived temperature and concentrations with the known (input) values.
Evaporation measurement by optical and radio wave scintillation
Authors: Kohsiek W. , Herben M.H.A.J.
Published: February 2023

The feasibility of measuring sensible heat flux by optical scintillation observations along a horizontal path has been demonstrated in the past (Wyngaard et al., 1978). The major advantage of the method is that it gives a line-averaged measurement. In contrast, other methods like temperature profiles, Bowen ratio or eddy correlation are point measurements. Line- or area-averaged measurements are often desirable for e.g. water balance studies and mesoscale meteorological investigations. A drawback of the scintillation method is that a semi-empirical relationship between the heat flux and the optically measured temperature structure parameter (CT2) is involved. This relation seems to be established only for an unstable atmosphere (Wyngaard and Clifford, 1978).
Multicolor Laser Altimeter for Atmospheric Pressure Measurements Over the Ocean: Experimental
Authors: Abshire J.B. , Kalshoven J.E.
Published: February 2023

Short-pulse multiwavelength laser ranging systems have been proposed to measure atmospheric pressure over the oceans (1). Recently, such systems also have been shown to be capable of accurately measuring ocean waveheight and wavelength (2,3). In our companion paper (4), the ocean reflected laser returns are calculated to have sharp features which are characteristic of the ocean surface depth profile, transmitter beam divergence and angle-of-incidence. These features are expected to be well correlated at both received wavelengths if the reflecting specular points are much larger than an optical wavelength, and if the average depth difference between successive points is larger than the transmitter pulse width.
Lidar Measurement of Atmospheric Carbon Dioxide at 4.88 Micrometers
Authors: Bufton Jack L. , Itabe Toshikazu , Korb C. Laurence
Published: February 2023

A lidar instrument based on pulsed carbon dioxide (CO2) lasers has been applied to the measurement of atmospheric CO2 concentration in the earth’s boundary layer. Two lines of the usual 9 μm P branch CO2 laser are translated to two wavelengths near 4.88 μm by a frequency doubling crystal for this measurement. One frequency-doubled line is strongly absorbed by atmospheric CO2 and the other acts as a reference in a conventional differential absorption lidar (DIAL) technique. Measurement of transmitter and receiver pulse energy on these two lines provide data necessary for computation of the differential absorption of a horizontal column of the earth’s atmosphere. Inversion of this data using CO2 spectroscopy results in a measure of CO2 concentration. Both laboratory data and demonstration field measurements have recently been made and results to date are presented and discussed.
Passive Radiometry for Vertical Sounding from Meteorological Satellites
Authors: Smith William L.
Published: February 2023

During the past two decades, passive infrared and microwave radiometers have been used to provide vertical temperature and moisture profiles from meteorological satellites. The infrared instruments have evolved from the medium spectral and low spatial resolution interferometer and grating spectrometer flown on the Nimbus III satellite in 1969 to the high spatial and low spectral resolution filter radiometers currently flying on the operational polar orbiting (NOAA) and geostationary (GOES) satellites. The microwave radiometers utilized have been of the conventional Dicke design. The evolution of the infrared sounding instruments has been driven by the need for high spatial resolution to probe the clear air interstices of the earth's broken cloud cover. Microwave sounders, which penetrate clouds, were initially much larger and heavier and consumed more power than infrared radiometers when compared to infrared sounders on a per channel per unit field-of-view basis. Advances in microwave radiometer technology have permitted the number of spectral channels to be increased, the field-of-view reduced, and the signal-to-noise ratio to be improved without a corresponding increase in the weight, volume, and power requirements.
Spectroscopic Considerations for Laser Remote Sensing of Atmospheric Species
Authors: Wilkerson Thomas D.
Published: February 2023

This paper discusses the close dependence of certain kinds of laser remote sensing measurements on spectroscopic detail--namely, properties of the species being measured, interferences from other spectra, and the spectrum of the laser light source. Our purpose is to summarize the processes that need to be taken into account in quantitative remote measurements, and to indicate the extensive literature now available.
Measurement of Gases Using CW Lasers, Differential Absorption, and Topographic Targets
Authors: Grant William B. , Webster Christopher R.
Published: February 2023

In this paper the specifications and measurement results of three CW laser systems which employ the Differential Absorption Lidar (DIAL) technique1, will be discussed: a helium neon (HeNe) laser system operating at 3.39 μm for the detection of CH4; a CO2 laser system operating at 9.5 μm using direct- or coherent- (heterodyne or modified homodyne) detection of ozone. The third system uses a tunable diode laser (TDL) system for detection of NO2 by scanning over an absorption line in the 6.2-μm band.