Search

The carrier density dependent current-voltage (J-V) characteristics of electrochemically prepared poly(3-methylthiophene) (P3MeT) have been investigated in Pt/P3MeT/Al devices, as a function of temperature from 280 to 84 K. In these devices, the charge transport is found to be mainly governed by different transport regimes of space charge limited conduction (SCLC). In a lightly doped device, SCLC controlled by exponentially distributed traps (Vl+1 law, l>1) is observed in the intermediate voltage range (0.5-2 V) at all temperatures. However, at higher bias (>2 V), the current deviates from the usual Vl+1 law where the slope is found to be less than 2 of the logJ-logV plot, which is attributed to the presence of the injection barrier. These deviations gradually disappear at higher doping level due to reduction in the injection barrier. Numerical simulations of the Vl+1 law by introducing the injection barrier show good agreement with experimental data. The results show that carrier density can tune the charge transport mechanism in Pt/P3MeT/Al devices to understand the non-Ohmic behavior. The plausible reasons for the origin of injection barrier and the transitions in the transport mechanism with carrier density are discussed. [ABSTRACT FROM AUTHOR]

Water-filled boreholes in cold ice refreeze in hours to days, and prior attempts to keep them open with antifreeze resulted in a plug of slush effectively freezing the hole even faster. Thus, antifreeze as a method to stabilize hot-water boreholes has largely been abandoned. In the hot-point drilling case, no external water is added to the hole during drilling, so earlier antifreeze injection is possible while the drill continues melting downward. Here, we use a cylindrical Stefan model to explore slush formation within the parameter space representative of hot-point drilling. We find that earlier injection timing creates an opportunity to avoid slush entirely by injecting sufficient antifreeze to dissolve the hole past the drilled radius. As in the case of hot-water drilling, the alternative is to force mixing in the hole after antifreeze injection to ensure that ice refreezes onto the borehole wall instead of within the solution as slush. [ABSTRACT FROM AUTHOR]

An exact problem of the electromagnetic wave propagation in a multilayer heteronanostructure with complex values of the dielectric constant (permittivity) is solved. The contribution to the refractive index of an additive to the dielectric constant due to the injected carriers is taken into account. A heterostructure based on a nanosystem used for the manufacture of lasers in the range 0.94–1.14 μm is considered. The methods and approaches used are also applicable for optimizing multilayer structures based on other solid solutions and those with several quantum wells. Based on the calculations of the temperature dependence of the radiation characteristics of injection lasers based on heteronanostructures, it was shown that the anomalous behavior of the temperature dependence of the threshold current is associated with a weakening of the waveguide properties of their active region. In accordance with the calculation results, the heteronanotructures parameters of injection lasers were optimized with respect to the thickness and dielectric properties of the waveguide nanolayer material, which made it possible to significantly reduce the temperature dependence of their radiative characteristics. [ABSTRACT FROM AUTHOR]

We study the effect of population inversion associated with the electron and hole injection in graphene p-i-n structures at the room and slightly lower temperatures. It is assumed that the recombination and energy relaxation of electrons and holes are associated primarily with the interband and intraband processes assisted by optical phonons. The dependences of the electron-hole and optical phonon effective temperatures on the applied voltage, the current-voltage characteristics, and the frequency-dependent dynamic conductivity are calculated. In particular, we demonstrate that at low and moderate voltages, the injection can lead to a pronounced cooling of the electron-hole plasma in the device i-section to the temperatures below the lattice temperature. However at higher voltages, the voltage dependences can be ambiguous exhibiting the S-shape. It is shown that the frequency-dependent dynamic conductivity can be negative in the terahertz (THz) range of frequencies at certain values of the applied voltage. The electron-hole plasma cooling substantially reinforces the effect of negative dynamic conductivity and promotes the realization of terahertz lasing. On the other hand, the heating of optical phonon system can also be crucial affecting the realization of negative dynamic conductivity and terahertz lasing at the room temperatures. [ABSTRACT FROM AUTHOR]

The junction-voltage temperature relationship of a laser diode is used to determine the temperature of the device in the range -20 to 120 °C. We consider changes that occur to this relationship when the diode is driven at its nominal operating current and above. It is found that estimates of the parameters that appear in a function fitted to the voltage-temperature data are sensitive to driving currents at and above the nominal operating current. Changes in parameter estimates are attributed to degradation due to surface recombination at facets occurring when the laser diode is overdriven. An indication of this degradation is the change in the ideality factor that occurs as the current to the device is raised. This work indicates that the temperature of the junction can be determined over the range -20 to 120 °C with a standard uncertainty of ≈0.5 °C. [ABSTRACT FROM AUTHOR]

Shift and injection currents are generated in the wurtzite semiconductors CdSe and CdS at 295 K using above-band-gap (hω>Eg) femtosecond pulses and detected via the emitted terahertz radiation; the optical beams are normally incident on samples with the optic axis in the plane of the surface. For optical intensities up to 75 MW cm-2 (or carrier density <1018 cm-3) the terahertz radiation amplitude shows the expected linear dependence and also varies with optical polarization and sample orientation consistent with the third-rank tensors that govern the current generation processes in the wurtzite structure. The largest shift currents are generated along the optical axis for light polarized along that axis. In CdSe with hω=1.80 eV (690 nm), the electron shift distance is ∼40% of the 0.25 nm bond length and the peak current density is 5 kA cm-2 for an optical intensity of 10 MW cm-2; for CdS the corresponding experiment at hω=3.0 eV (410 nm) gives a shift distance ∼80% of the 0.26 nm bond length with a peak current density of 50 kA cm-2 for an incident intensity of 75 MW cm-2. For injection current produced in CdSe with circularly polarized 690 nm excitation, electrons are injected with an average speed of 9 km s-1; this is ∼3% of the group velocity for electrons excited with the same energy. The corresponding values for CdS excited at 410 nm are 20 km s-1 and 2%. From the temporal characteristics of the terahertz emission for injection currents in CdS we deduce that the electron momentum scattering time is <100 fs, consistent with mobility studies. [ABSTRACT FROM AUTHOR]

Laser pulse control of the photoinduced 90 fs charge injection from perylene into the conduction band of TiO2 is studied theoretically. The approach accounts for the electronic-ground state of the dye, the first excited state, the ionized state formed after charge injection, and the continuum of the electronic states in the conduction band, all defined vs a single reaction coordinate. To address different control tasks optimal control theory is combined with a full quantum dynamical description of the electron-vibrational motion accompanying the charge injection process. First it is proved in which way the charge injection time can be changed by tailored laser pulses. In a second step a pump-dump scheme from the perylene ground state to the first excited electronic state and back to the ground state is discussed. Because of the strong coupling of the excited perylene state to the band continuum of TiO2 this control task is more suited to an experimental test than the direct control of the charge injection. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Magnetization switching provoked by spin injection is studied in Ni nanowires of various sizes and morphologies. The response of the magnetization to current injection is measured as a function of the amplitude of the current, the temperature, and the symmetry of the interfaces. The efficiency of the response of the magnetization of spin injection is a decreasing function of the temperature, does not depend on the current sign, and occurs only in the case of asymmetric interfaces. It is shown that the switching provoked by spin injection is not affected by the presence of a magnetic domain inside the layer. Some consequences in terms of spin transfer or exchange torque are discussed. [ABSTRACT FROM AUTHOR]

We propose a contact structure for InAs/GaSb multilayers, such that electrons and holes are selectively injected in alternating layers. This enables the implementation of a far-infrared lateral current injection laser based on the InAs/GaSb superlattice. Preliminary calculation of the gain shows that both surface- and edge-emitting designs are possible. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract Noise is often present in real datasets used for training Machine Learning classifiers. Their disruptive effects in the learning process may include: increasing the complexity of the induced models, a higher processing time and a reduced predictive power in the classification of new examples. Therefore, treating noisy data in a preprocessing step is crucial for improving data quality and to reduce their harmful effects in the learning process. There are various filters using different concepts for identifying noisy examples in a dataset. Their ability in noise preprocessing is usually assessed in the identification of artificial noise injected into one or more datasets. This is performed to overcome the limitation that only a domain expert can guarantee whether a real example is indeed noisy. The most frequently used label noise injection method is the noise at random method, in which a percentage of the training examples have their labels randomly exchanged. This is carried out regardless of the characteristics and example space positions of the selected examples. This paper proposes two novel methods to inject label noise in classification datasets. These methods, based on complexity measures, can produce more challenging and realistic noisy datasets by the disturbance of the labels of critical examples situated close to the decision borders and can improve the noise filtering evaluation. An extensive experimental evaluation of different noise filters is performed using public datasets with imputed label noise and the influence of the noise injection methods are compared in both data preprocessing and classification steps. [ABSTRACT FROM AUTHOR]

Describes a scheme for developing a synchronizable, injection-locked, Q-switched, mode-locked and cavity-dumped 10-atmosphere carbon dioxide lasers. Principle of operation; Information on the amplifier module; Details of the complete optical and electrical arrangement for the laser system.

Presents an analysis of the lateral-mode behavior of a semiconductor-laser array after including the effect of injected charge carriers on the active-layer dielectric constant. Effect of an index profile that peaks at the center of the emitter where the gain is maximum on the behavior of a gain-guided array; Features of phase-locked index-guided arrays; Evaluation of the coupling coefficients.

Discusses an observation of large injection current pulses in a simple circuit containing forward biased p-i-n device structures at low temperatures. Diagram of a forward p-i-n diode at low temperatures; Comparison of the pulse rate with the blackbody source.

Investigates some of the properties of strained-layer quantum-well heterostructure (SL-QWH) current injection lasers to evaluate the potential of the strained-layer lasers. Cross section of SL-QWH laser grown by molecular beam epitaxy; Room temperature emission spectra for SL-QWH laser; Degradation of a SL-QWH laser during 1000 h of operation.

Presents a study which examined the modulation response of a tunneling injection laser by an analytic solution of the rate equations taking into account carrier transport effects. Disadvantages of semiconductor quantum well (QW); Features of the tunneling injection laser; Comparison of the modulation response.

Presents information on a study which described the quantum-well injection laser in terms of the appropriate quasi-Fermi levels and Einstein coefficient for stimulated emission. Methods; Results; Discussion.

Focuses on a study which investigated the thermal dissociation of PH[sub3] and NH[sub3] injected through a tantalum-based high-pressure gas-injection cell. Pyrolytic behavior of PH[sub3] and NH[sub3]; Description of the beam-flux patterns of PH[sub3] and NH[sub3]; Determination of the substitutional nitrogen species.

Reports the observation of frequency locking and quasiperiodicity in a modulated external cavity injection laser. Order of appearance of the frequency-locked regions; Behavior of the laser when modulated at frequencies other than integer multiples of the cavity resonance frequency; Agreement of the observed behavior with a rate equation model.

To date, the shortest wavelength of an ultraviolet current-injection nitride laser has been limited to ∼340 nm. This begs the question of whether there is a fundamental limitation that restricts the realization of injection lasers below this wavelength. This letter investigates this issue. We find that, apart from being the decisive factor for the crystalline quality of nitride epitaxial layers, residual strain plays yet another crucial role in modifying the band structure of (Al,Ga)N quantum wells. A critical analysis of quantum-confinement effects, strain, and the polarization properties of strained (Al,Ga)N layers is essential for the realization of deep ultraviolet laser diodes. [ABSTRACT FROM AUTHOR]

Abstract Beam quality preservation in the external injection scheme is one of the key missing milestones towards staging of plasma-wakefield accelerators, a prerequisite for their utilisation in particle physics or other applications requiring high energy beams. This topic will be studied at FLASHForward, a unique beam-driven plasma wakefield acceleration facility currently under construction at DESY (Hamburg, Germany), in the frame of the FLASHForward X-2 experiment. High-quality 1 GeV-class electron beams from the free-electron laser FLASH with μ m-emittances, kA-scale currents, and less than 100 fs durations will be utilised to generate driver–witness pairs by using a mask in a dispersive section. In this contribution the physics case and the current status of the FLASHForward X-2 experiment are reviewed. The experimental installation is described, with a focus on the electron beamline. Electron beam dynamics and particle-in-cell simulations are presented. [ABSTRACT FROM AUTHOR]

Abstract This article introduces an analytical formalism for the calculation of the evolution of beam moments and the transverse emittance for beams which are externally injected into plasma wakefield accelerators. This formalism is then applied to two scenarios with increasing complexity — a single beam slice without energy gain and a single beam slice with energy gain, both propagating at a fixed co-moving position behind the driver. The obtained results are then compared to particle-in-cell (PIC) simulations as well as results obtained using an semi-analytic numerical approach (SANA) (Mehrling et al., 2016). We find excellent agreement between results from the analytical model and from SANA and PIC. Highlights • Uncorrelated emittance growth in a blowout can be described by an analytic model. • It reproduces results for a beam slice with less effort than existing methods. • The model provides a decoherence time for a parameter mismatch in external injection. [ABSTRACT FROM AUTHOR]

Incomplete luteal regression after treatment with a single dose of prostaglandin F2α during an Ovsynch protocol decreases fertility to timed artificial insemination (TAI). To increase the proportion of cows with complete luteal regression and subsequently pregnancy per artificial insemination (P/AI), an additional treatment with PGF2α 24 h after the first has been recommended. A systematic review of the literature and meta-analytical assessment were performed with the objective of evaluating the effects of adding a second PGF2α treatment during the Ovsynch protocol on luteal regression and reproductive performance in lactating dairy cows. Based on the heterogeneity among the experimental treatments, a fixed or a random effects meta-analysis was conducted. Reproductive outcomes of interest were luteal regression at the end of the Ovsynch protocol, and P/AI measured 32 to 39 d after TAI. Seven randomized controlled experiments from 6 published manuscripts including 5,356 cows with the primary objective to evaluate the effect of an additional treatment with PGF2α during the Ovsynch protocol on P/AI were used. Information regarding luteal regression at the end of the Ovsynch protocol was available for 1,856 cows. Adding a second PGF2α treatment on d 8 during the Ovsynch protocol increased the relative risk (RR) of complete luteal regression at the end of the Ovsynch protocol (RR = 1.14; 95% confidence interval = 1.10 to 1.17) using a fixed effects model and the RR for pregnancy (RR = 1.14; 95% confidence interval = 1.06 to 1.22) 32 d after TAI using a fixed effects model. No heterogeneity was observed among the 6 manuscripts regarding complete luteal regression (P = 0.450) and P/AI (P = 0.942). In summary, there was a clear benefit of an additional PGF2α treatment during the Ovsynch protocol on luteal regression (+11.6 percentage units) and on P/AI (+4.6 percentage units). [ABSTRACT FROM AUTHOR]

We propose an asymmetric electron-hole model of an injection semiconductor quantum-dot laser, which correctly allows for relaxation at transitions between the electron and hole levels. Steady-state solutions of the proposed model, conditions for the simultaneous operation at transitions between the ground and first excited state levels, and relaxation oscillations in the two-wave lasing regime are studied. It is shown that the model can be simplified when the relaxation between hole levels is much faster than the relaxation between electron levels. [ABSTRACT FROM AUTHOR]

The electrical and optical properties of InGaN LEDs with different threading dislocation densities (TDDs) were investigated. LEDs with low TDDs exhibited low forward voltage and high injection efficiency compared with LEDs with high TDDs. The effect of TDDs on the electrical properties of InGaN LEDs was attributed to efficient carrier injection into the QWs brought about by increased transverse carrier mobility in the InGaN layer resulting from reductions in carrier scattering around dislocation cores. In terms of optical properties, LEDs with low TDDs exhibited high peak efficiency and substantial efficiency droops under increased current densities, whereas LEDs with high TDDs showed low peak efficiency and minimal droops under the same condition. These trends can be explained by the correlations of high TDDs with increased dominance of nonradiative recombination and pronounced suppression of peak efficiency under low current densities. [ABSTRACT FROM AUTHOR]

We develop a theoretical framework for modeling of semiconductor laser coupled to an external fiber-optic ring resonator. The developed approach has shown good qualitative agreement between theoretical predictions and experimental results for particular configuration of a self-injection locked DFB laser delivering narrow-band radiation. The model is capable of describing the main features of the experimentally measured laser outputs such as laser line narrowing, spectral shape of generated radiation, mode-hoping instabilities and makes possible exploring the key physical mechanisms responsible for the laser operation stability. [ABSTRACT FROM AUTHOR]

Simultaneous two-state lasing is a unique property of semiconductor quantum-dot (QD) lasers. This not only changes steady-state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single-state laser devices, we find a strong suppression of dynamical instabilities in two-state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all-optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required. [ABSTRACT FROM AUTHOR]

Focuses on an experiment which examined the modal gain of an InAs/GaAs self-organized quantum dot (QD) laser. Potential of injection lasers with self-organized QD active regions for low threshold current density; Results of experiments on InAs self-organized QD; Photocurrent measurements to determine modal gain; Findings.

Compared to intravitreal injection, subretinal injection has more direct effects on the targeting cells in the subretinal space, which provides a new therapeutic method for vitreoretinal diseases, especially when gene therapy and/or cell therapy is involved. To date, subretinal delivery has been widely applied by scientists and clinicians as a more precise and efficient route of ocular drug delivery for gene therapies and cell therapies including stem cells in many degenerative vitreoretinal diseases, such as retinitis pigmentosa, age-related macular degeneration, and Leber's congenital amaurosis. However, clinicians should be aware of adverse events and possible complications when performing subretinal delivery. In the present review, the subretinal injection used in vitreoretinal diseases for basic research and clinical trials is summarized and described. Different methods of subretinal delivery, as well as its benefits and challenges, are also briefly introduced. [ABSTRACT FROM AUTHOR]

A terahertz quantum-cascade (QC) vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated with over 5 mW power in continuous-wave and single-mode operation above 77 K, in combination with a near-Gaussian beam pattern with a full-width half-max divergence as narrow as ~5° ×5°, with no evidence of thermal lensing. This is realized by creating an intra-cryostat VECSEL cavity to reduce the cavity loss and designing an active focusing metasurface reflector with low power dissipation for efficient heat removal. Also, the intra-cryostat configuration allows the evaluation of QC-VECSEL operation vs. temperature, showing a maximum pulsed mode operating temperature of 129 K. While the threshold current density in the QC-VECSEL is higher compared to that in a conventional edge-emitting metal-metal waveguide QC-laser, the beam quality, slope efficiency, maximum power, and thermal resistance are all significantly improved [ABSTRACT FROM AUTHOR]

The exact problem of electromagnetic wave propagation in a multilayer nanostructure with complex values of dielectric permittivity is solved. The contribution to the refractive index of an additive to the dielectric constant connected with the injected carriers is taken into account. Within the framework of this problem, it is shown that an anomalous temperature dependence of the threshold current of injection lasers based on nanoheterostructures is related to the anti-waveguide action of injected carriers. A quantum-well heterostructure based on InGaAs/AlGaAs/GaAs nanosystems used for fabrication of 0.94-1.14 μm lasers is considered. The applied techniques and approaches are also acceptable for the optimization of multilayer nanostructures based on other solid solutions. As an optical model of the active region of injection lasers based on nanostructures, a planar multilayer dielectric waveguide with complex values of dielectric permittivity in the layers is considered. It is shown that with decreasing thickness of the active region of injection lasers, the dependence of the mode gain on the local gain is essentially sublinear. The reason for this is the antiwaveguide action of electrons. The results of calculations of the temperature dependence of the threshold current of injection lasers indicate the presence of a critical point Tc, at which a sharp decrease in the characteristic temperature occurs. The performed calculations and optimization of the temperature dependence of emission characteristics of injection lasers based on nanostructures show that the anomalous behavior of the temperature dependence of the threshold current is also associated with the weakening of the waveguide properties of theirs active region. [ABSTRACT FROM AUTHOR]

This paper proposes a circuit model for injection lasers with functionally integrated optical-radiation modulators. This model takes into account the design and structural features of the functionally-integrated injection laser modulators (FIILMs), as well as the effect exerted by the spatial distributions of electrons, holes, and photons in the FIILMs' active region on the behavior of the physical processes there. [ABSTRACT FROM AUTHOR]

Copyright of Journal of College of Education for Pure Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Numerical simulation results reveal that introducing polarization-induced doping hole injection layer (HIL) in the DUV-LEDs results in a downward band-bending at the EBL/HIL interface, which causes more severe electron leakage. The effect of optimizing EBL thickness on the performance of DUV-LEDs was investigated to mitigate the side-effects due to the introduction of polarization-induced doping HIL. The experimental results show that as the EBL thickness increases, the external quantum efficiency (EQE) and wall-plug efficiency (WPE) of the DUV-LEDs increase and then decrease, while the efficiency droop in an opposite trend. The maximum EQE and WPE of 5.95% and 5.48%, respectively, were achieved when the EBL thickness was 20 nm. Meanwhile, increasing the EBL thickness can improve the DUV-LED reliability. However, an excessively thick EBL will deteriorate the reliability due to generating more Joule heat. Therefore, the reliability of DUV-LED was optimal when the EBL thickness was 25 nm. • Experimental studies were performed based on the polarization-induced doping hole injection layer structure. • Introducing polarization-induced doping hole injection layer causes severe electron leakage. • Increasing the thickness of the triangular hole potential barrier hinders hole injection. • DUV-LED reliability does not monotonically improve as EBL thickness increases. [ABSTRACT FROM AUTHOR]

Diffusion injection lasers based on PbSnSe alloy, emitting in a wide spectral range of 10-46.5 μm depending on the composition and temperatures are fabricated. A technology for growing high-quality single crystals from the vapor phase under conditions of free growth is developed. The dependences of the total emission intensity on the pump current and the emission spectra of injection lasers based on PbSnSe are studied. In these samples, lasing of long-wavelength radiation to a record wavelength of 46.5 μm is achieved. [ABSTRACT FROM AUTHOR]

Studies individual spatial modes of a phase-locked injection laser array observed through spectral selection and selected with an external mirror. Method of the study; Results and discussion; Conclusion.

Focuses on a study which investigated the potential use of a superlattice system for midwave infrared injection laser applications. Information on the use of the superlattice in multispectral infrared applications; Conditions that promote short Auger lifetimes with increasing temperatures; Comparison of the radiative recombination and Auger lifetimes at threshold carrier densities.

The power characteristics of quantum-well lasers with asymmetric barrier layers, which represent a novel type of injection laser, are calculated on the basis of an extended model taking into account asymmetry in the filling of electron and hole states. The electron-hole asymmetry is shown to have no significant effect on the characteristics of these lasers. Even in the presence of intermediate layers (located between the quantum well and each of the two asymmetric barrier layers), where parasitic electron-hole recombination does occur, the internal differential quantum efficiency of such a laser exhibits only a weak dependence on the pump current and remains close to unity; therefore, the light-current characteristic remains linear up to high pumping levels. [ABSTRACT FROM AUTHOR]

Certain experiments in quasi-isobaric supercritical injection remain unexplained by the current state of theory: Without developing a constant value potential core as expected from the mechanical view of break-up, density is observed to drop immediately upon entering the chamber. Furthermore, this phenomenon has never been captured in computational fluid dynamics (CFD) despite having become a de facto standard case for real fluid CFD validation. In this paper, we present strong evidence for a thermal jet disintegration mechanism (in addition to classical mechanical break-up) which resolves both the theoretical and the computational discrepancies. A new interpretation of supercritical jet disintegration is introduced, based on pseudo-boiling, a nonlinear supercritical transition from gas-like to liquid-like states. We show that thermal disintegration may dominate classical mechanical break-up when heat transfer takes place in the injector and when the fluid state is sufficiently close to the pseudo-boiling point. A procedure which allows to capture subsided cores with standard CFD is provided and demonstrated. [ABSTRACT FROM AUTHOR]

Continuous-wave blue semipolar(2021) III-nitride laser diodes were fabricated with highly vertical, smooth, and uniform mirror facets produced by chemically assisted ion beam etching. Uniform mirror facets are a requirement for accurate experimental determination of internal laser parameters, including internal loss and injection efficiency, which were determined to be 9 cm-1 and 73%, respectively, using the cavity length dependent method. The cavity length of the uncoated devices was varied from 900 µm to 1800 µm, with threshold current densities ranging from 3 kA/cm² to 9 kA/cm² and threshold voltages ranging from 5.5V to 7 V. The experimentally determined internal loss was found to be in good agreement with a calculated value of 9.5 cm-1 using a 1D mode solver. The loss in each layer was calculated and in light of the analysis several modifications to the laser design are proposed. [ABSTRACT FROM AUTHOR]

An analytical expression of transient four-wave mixing (TFWM) in inverted semiconductor with carrier-injection pumping was derived from both the density matrix equation and the complex stochastic stationary statistical method of incoherent light. Numerical analysis showed that the TFWM decayed decay is towards the limit of extreme homogeneous and inhomogeneous broadenings in atoms and the decaying time is inversely proportional to half the power of the net carrier densities for a low carrier-density injection and other high carrier-density injection, while it obeys an usual exponential decay with other decaying time that is inversely proportional to half the power of the net carrier density or it obeys an unusual exponential decay with the decaying time that is inversely proportional to a third power of the net carrier density for a moderate carrier-density injection. The results can be applied to studying ultrafast carrier dephasing in the inverted semiconductors such as semiconductor laser amplifier and semiconductor optical amplifier. [ABSTRACT FROM AUTHOR]

We present a numerical analysis of 50 Gbaud coherent detection enabled by injection locked lasers and line coding. The coherent receiver was tested with respect to an ideal receiver for two higher order modulation formats (16-QAM, QPSK) and under diverse operating regimes relating to the slave laser linewidth properties, the injection level and the frequency detuning between the incoming signal and the slave laser. The impact of the slave laser properties and line coding techniques on the receiver performance is highlighted showing that the technique could be used as a practical solution in order to enable low-cost and short reach n × 100 Gb/s Ethernet communication systems with the potential of flexibility in terms of the data rate. [ABSTRACT FROM AUTHOR]

Three-dimensional (3-D) computational code was implemented to solve conservation equations based on finite volume method as to simulate 1.8 L Ford diesel engine. Velocity and pressure of each computational cell is achieved by SIMPLE (semi-implicit method for pressure-linked equations) algorithm. For the exergetic aspect, the initial condition is set at 0.1 MPa and 300 K. The engine modeling is performed with 130 °, 140 °, and 150 ° with respect to x-axis under 1500 and 2500 rpm engine speeds. The results, however, indicate better air/fuel mixture (near stoichiometric equivalence ratio) for 130 ° of injection angle, albeit smaller spray droplets (lower sauter mean diameter) were introduced with 140 °. It is seen that higher soot and NOx mass fraction is attributed to 1500 rpm engine speed. The highest NOx and soot are exhausted at 130 ° and 150 ° of injection, respectively. Second law efficiency was calculated for different spray angle and engine speed schemes such that 36.62%, 30.2%, and 32.07% are associated with 130 °, 140 °, and 150 ° of injection angle under 1500 rpm, respectively. In terms of engine performance, that is, indicated mean effective pressure, indicated specific fuel consumption, and temperature, the best performance metrics are of 130 ° equal to 15.4 bar, 0.3856 kg/kW-h, and 2074.97 K under 1500 rpm, respectively. Instant irreversibility rate is the highest amount with peak value of 17.48 J/deg for 130 deg-1500 rpm, while 140 ° shows higher mean irreversibility rate over crank angle ( CA) period. [ABSTRACT FROM AUTHOR]

A mathematical model is proposed that can be used for numerical analysis of the dynamics of processes in injection lasers with allowance for their structural features; nonuniform spatial distributions of electrons, holes, and photons; and various mechanisms of radiative recombination. Results of numerical modeling of double-heterostructure injection lasers performed using the proposed model are compared to the results obtained using the equations of laser kinetics. Boundaries of applicability of these models are considered. [ABSTRACT FROM AUTHOR]

The internal concentration represented by the critical body residue (CBR) is an ideal indicator to reflect the intrinsic toxicity of a chemical. Whilst some studies have been performed on CBR, the effect of exposure route on internal toxicity has not been investigated for fish. In this paper, acute toxicity data to fish comprising LC and LD values were used to investigate CBR. The results showed that exposure route can significantly affect the internal concentration. LD and CBR calculated from LC and BCF both vary independently of hydrophobicity as expressed by log K; conversely, LC is related to log K. A poor relationship was observed between LC and LD, but the relationship can be improved significantly by introduction of log K because log CBR is positively related to log LD. The parallel relationship of log CBR-log K and log LD-log K indicates that LD does not reflect the actual internal concentration. The average LD is close to the average CBR for less inert and reactive compounds, but greater than the average CBR for baseline compounds. This difference is due to the lipid fraction being the major storage site for most of the baseline compounds. Investigation on the calculated and observed CBRs shows that calculated CBRs are close to observed CBRs for most of compounds. However, systemic deviations of calculated CBRs have been observed for some compounds. The reasons for these systemic deviations may be attributed to BCF, equilibrium time and experimental error of LC. These factors are important and should be considered in the calculation of CBRs. [ABSTRACT FROM AUTHOR]

The classical problem of a semiconductor laser subject to polarized injection is revisited. From the laser rate equations for the transverse electric (TE) and transverse magnetic (TM) modes, we first determine the steady states. We then investigate their linear stability properties and derive analytical expressions for the steady, saddle-node, and Hopf bifurcation points. We highlight conditions for bistability between pure- and mixed-mode steady states for the laser subject to either TE or TM injection. To our knowledge, the first case has not been documented yet. An important parameter is the ratio of the polarization gain coefficients and we explore its effect on the stability and bifurcation diagrams. [ABSTRACT FROM AUTHOR]

We generate 555.8-nm light with sub-MHz linewidth through the use of laser injection locking of a semiconductor diode at 1,111.6 nm, followed by frequency doubling in a resonant cavity. The integrity of the injection lock is investigated by studying an offset beat signal between slave and master lasers, by performing spectroscopy on the $$(6s)^{2}\, {}^{1}S_{0}\hbox{--}(6s6p)\,{}^{3}P_{1}$$ transition in magneto-optically trapped ytterbium, and by demonstrating additional laser cooling of $${}^{171}\hbox {Yb}$$ with the 555.8-nm light in a dual-wavelength magneto-optical trap (MOT). For the $${}^{1}S_{0}$$ - $$\,^{3}P_{1}$$ spectroscopy, we confirm the linear dependence between ground-state linewidth and the intensity of an off-resonant laser, namely that used to cool Yb atoms in a $${}^{1}S_{0}$$ - $$\,^{1}P_{1}$$ magneto-optical trap. A temperature of 60 μK is produced for $${}^{171}\hbox {Yb}$$ in the dual-wavelength MOT. Our results demonstrate the suitability of injection-locked 1,100-1,130-nm laser diodes as a source for sub-MHz linewidth radiation in the yellow-green spectrum. [ABSTRACT FROM AUTHOR]