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Quantum Electronics, IEEE Journal of

Issue 9 • Date Sep 1996

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Displaying Results 1 - 22 of 22
  • Backward optical parametric oscillators and amplifiers

    Page(s): 1574 - 1582
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    Degenerate backward optical parametric oscillators and amplifiers have been considered, for the first time, to the best of our knowledge. When the pump intensity is four times the threshold pump intensity, the conversion efficiency reaches a maximum value. On the other hand, for nondegenerate optical parametric oscillators, the conversion efficiency always increases as the pump intensity increases. This behavior is different from those for forward optical parametric oscillators. In either configuration, the oscillation can occur without an external feedback. There is, however, a distributed feedback provided through the opposite propagation directions of the signal and idler. The threshold pump intensities for the oscillators can be achieved by the lasers currently available based on quasi-phase matching in several structures. As the input intensity for the backward parametric wave increases, the gain for this wave decreases dramatically if the pump intensity is on the order of the threshold or higher. When the input intensity is much larger than the threshold pump intensity, there is almost no gain regardless of the level of the pump intensity View full abstract»

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  • Numerical analysis of the whispering gallery modes by the finite-difference time-domain method

    Page(s): 1583 - 1587
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    The finite-difference time-domain (FDTD) method is used to analyze the whispering-gallery modes of microdisk lasers. The method takes no a priori assumption. It solves the Maxwell's equations directly while taking into account the actual structure of the microdisk. The numerical results are in agreement with experimentally measured spectrum. Our Q values, however, are higher than previously published theoretical results. By calculating the resonant wavelengths and Q factors for different disk sizes, we demonstrate that the FDTD can be used to optimize the design of microdisk lasers View full abstract»

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  • Investigation of high-efficiency surface-emitting lasers with blazed grating outcouplers

    Page(s): 1596 - 1605
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    Grating outcouplers for use in grating coupled surface emitting semiconductor lasers were investigated. For this purpose, horizontal cavity InGaAs-AlGaAs laser oscillators, each integrated with one detuned grating outcoupler, were fabricated using electron beam lithography and chemically assisted ion beam etching. Outcouplers with gratings of both rectangular and blazed profile as well as of different toothwidth-to-period ratios were fabricated and evaluated. Superior differential quantum and surface emission efficiencies of 56% and 84%, respectively, were measured for lasers with optimized blazed outcouplers. This shows that efficiencies comparable to those of conventional edge emitting lasers can be achieved. The measured surface emission efficiencies were also compared with predictions from a theoretical grating analysis View full abstract»

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  • Modeling of integrated erbium-doped waveguide amplifiers with overlapping factors methods

    Page(s): 1685 - 1694
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    An analysis of the applicability of overlapping factors methods to the modeling of integrated erbium-doped waveguide amplifiers is presented. These methods offer as main advantage a considerable seduction in computation time without a decrease in their effective accuracy. We propose an extension of previous overlapping factors methods in order to model highly erbium-doped waveguide amplifiers. New sets of parameters related to the relevant upconversion and cross-relaxation mechanisms are introduced. Some numerical examples illustrate both working-conditions dependent and independent overlapping factors main dependences, which are fully explained. Finally, the accuracies of the results obtainable by both methods are examined and interpreted and the reduction in computation time is considered View full abstract»

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  • Continuously tunable high-pressure CO2 laser for spectroscopic studies on trace gases

    Page(s): 1549 - 1559
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    A high-pressure CO2 laser with unique characteristics in terms of continuous tunability and emission bandwidth is presented. It is operated at a pressure of 11.5 bar and transversely excited by short, high-voltage pulses generated by a double LC inversion circuit. Auxiliary discharges parallel to the electrodes provide a sufficient free-electron density through UV ionization of the laser gas mixture. The laser resonator consists of a near-grazing-incidence grating setup in which the grating is positioned at a large incidence angle of 77°. A theoretical model for the calculation of the emission bandwidth is presented and its predictions are compared to direct measurements and show excellent agreement. The achieved very narrow bandwidth of 0.018 cm-1 constitutes the ultimate wavelength resolution of any detection system using this laser as radiation source. It allows the resolution of any fine structure in the spectra of absorbing gases at atmospheric pressure. Continuous tunability has been achieved over 76 cm-1 between 932 cm-1 and 1088 cm -1 with minimum pulse energies in excess of 10 mJ. The narrow bandwidth precludes the occurrence of mode-pulling effects so that the laser exhibits a linear wavelength tuning behavior throughout the entire emission range. The calibration of the laser wavelength is performed by photoacoustic measurements on low pressure CO2 gas. An absolute accuracy of ±10-2 cm-1 is achieved. A great potential improvement in detection selectivity can thus be expected from a scheme with the high-pressure CO2 laser as radiation source View full abstract»

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  • High-reliability 1.3-μm InP-based uncooled lasers in nonhermetic packages

    Page(s): 1606 - 1614
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    We report the first uncooled nonhermetic 1.3-μm InP-based communication lasers that have reliability comparable to their hermetically packaged counterparts for possible applications in fiber in the loop and cable TV. The development of reliable nonhermetic semiconductor lasers would not only lead to the elimination of the costs specifically associated with hermetic packaging but also lead the way for possible revolutionary low-cost optoelectronic packaging technologies. We have used Fabry-Perot capped mesa buried-heterostructure (CMBH) uncooled lasers with both bulk and MQW active regions grown on n-type InP substrates by VPE and MOCVD. We find that the proper dielectric facet passivation is the key to obtain high reliability in a nonhermetic environment. The passivation protects the laser from the ambient and maintains the proper facet reflectivity to achieve desired laser characteristics. The SiO facet passivation formed by molecular beam deposition (MBD) has resulted in lasers with lifetimes well in excess of the reliability goal of 3,000 hours of operation at 85°C/90% RH/30 mA aging condition. Based on extrapolations derived experimentally, we calculate a 15-year-average device hazard rate of <300 FITs (as against the desired 1,500 FITs) for the combination of thermal-and humidity-induced degradation at an ambient condition of 45°C/50% RH. For comparison, the average hazard rate at 45°C and 15 years of service is approximately 250 FITs for hermetic lasers of similar construction. A comparison of the thermal-only degradation (hermetic) to the thermal plus humidity-induced degradation (nonhermetic) indicates that the reliability of these nonhermetic lasers is controlled by thermal degradation only and not by moisture-induced degradation. In addition to device passivation for a nonhermetic environment, MBD-SiO maintains the optical, electrical, and mechanical properties needed for high-performance laser systems View full abstract»

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  • Ultrafast pulse generation in photoconductive switches

    Page(s): 1664 - 1671
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    Carrier and field dynamics in photoconductive switches are investigated by electrooptic sampling and voltage-dependent reflectivity measurements. We show that the nonuniform field distribution due to the two-dimensional nature of coplanar photoconductive switches, in combination with the large difference in the mobilities of holes and electrons, determine the pronounced polarity dependence. Our measurements indicate that the pulse generation mechanism is a rapid voltage breakdown across the photoconductive switch and not a local field breakdown View full abstract»

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  • A novel cladding structure for semiconductor quantum-well lasers with small beam divergence and low threshold current

    Page(s): 1588 - 1595
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    A novel cladding structure is proposed and analyzed for semiconductor quantum-well lasers to achieve a small vertical-beam divergence and a low threshold current density simultaneously. This cladding structure is designed to guide a wide optical mode but with a high peak intensity in quantum wells. The wide expansion of the optical mode results in a small beam divergence. In addition, the high optical Intensity in quantum wells causes a low threshold current density. This novel cladding structure is optimized. The result shows that this type of cladding structures can achieve a beam divergence as small as 14.6° while the threshold current density remains small View full abstract»

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  • Spatiotemporal evolution of probe beams guided between bright solitons of nondegenerate frequencies

    Page(s): 1657 - 1663
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    We analyzed an alternative approach for guiding parallel signal beams nested between noninteracting fundamental bright spatial solitons. The numerical results show that stable signal-wave guiding without a cross-talk is obtainable even at small-intensity fluctuations of the control beams (±10%) and at nonperfect alignment of the signal beams with respect to the channels formed by the solitons. Conditions under which the temporal changes of the signal pulses could be asymptotically reduced are discussed View full abstract»

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  • Temperature and gain dynamics in flashlamp-pumped Er:YAG

    Page(s): 1636 - 1644
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    A novel optical transmission method was used for measuring transient temperature dynamics inside an Er:YAG laser crystal during optical pumping with flashlamp pulses of different duration and spectral composition. Time-resolved measurements of the crystal gain at 2.94 μm were also performed for the same set of pumping conditions. The results are compared with predictions of a theoretical model for gain and temperature dynamics during optical pumping of Er:YAG. A good spatial resolution of the implemented temperature measurement method was utilized also to determine the lateral temperature profiles inside the laser rod under various pumping conditions View full abstract»

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  • Modeling of laser-pumped Tm and Ho lasers accounting for upconversion and ground-state depletion

    Page(s): 1645 - 1656
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    Models for numerical simulations of laser-pumped thulium- and thulium-holmium-doped lasers have been developed. In the models, upconversion losses and ground-state depletion in both thulium and holmium are accounted for, as well as spatial dependencies of the pump and resonator modes. The models apply to CW operation and to the build-up of population inversion prior to lasing in pulsed modes of operation. It is shown that upconversion losses in Tm:Ho:YAG significantly reduce the output from the laser in both CW and Q-switched mode. Simulations of CW lasers show good agreement with experimental results View full abstract»

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  • Coherent current control in semiconductors: a susceptibility perspective

    Page(s): 1570 - 1573
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    We show that the all-optical generation and control of dc current in semiconductors, also known as coherent current control, can be described within the standard framework of nonlinear optics using perturbative susceptibilities. In particular, we find that such effects arise from zero frequency divergences in the susceptibilities; this identification provides a novel and convenient method to classify the various contributions in the response. However, these physical divergences are distinct from other unphysical divergences that are commonly encountered and which have led to incorrect results elsewhere in the literature. The susceptibility viewpoint offered here allows one to understand the optical response for both resonant and nonresonant excitation, exposes the relationship between second- and third-order (and higher) processes, and will provide a natural framework in which to include dissipative effects View full abstract»

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  • A simplified analytic model for gain saturation and power extraction in the flowing chemical oxygen-iodine laser

    Page(s): 1525 - 1536
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    This paper describes the development of a simplified saturation model (SSM) for predicting power extraction from a chemical oxygen-iodine laser (COIL). Using the Fabry-Perot gain saturation assumption, analytic expressions for COIL extraction efficiency are presented for both constant-density and variable-density cavity conditions. The model treats mirror scattering, nonsaturable distributed losses, and diffractive losses from the mode-limiting aperture and is shown to be in excellent agreement with experimental COIL power extraction data. A comparison of the model with the Rigrod power extraction model is presented showing that the Rigrod model accurately predicts COIL extraction efficiency only in the limit that the COIL device no longer behaves as a transfer laser View full abstract»

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  • Lateral spatial effects of feedback in gain-guided and broad-area semiconductor lasers

    Page(s): 1630 - 1635
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    Starting from Fresnel diffraction theory, we derive analytic expressions for the lateral spatial dependence of feedback fields for the cases of conventional and phase-conjugate optical feedback. By using numerical simulations we show that for narrow-stripe gain-guided lasers, both types of optical feedback from an external cavity can convert the twin-lobed far fields into a nearly single-lobed far field. We also find that conventional and phase-conjugate feedbacks in broad-area lasers induce a spatial modulation of the lateral field that increases the tendency for filamentation at moderate (-30 dB) feedback levels View full abstract»

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  • Analytical treatment of transverse-mode evolution in free electron lasers

    Page(s): 1544 - 1548
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    The problem of the small-signal transverse-mode evolution in free electron lasers is discussed within the framework of an analytical treatment. The analysis is based on the formalism of the amplitude approximants and includes the effect of high gain and inhomogeneous broadening contributions. Mode distortion and focusing effects are derived fairly straightforwardly. We comment on the possibility of including the pulse propagation mechanism View full abstract»

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  • Effects of plate thickness and stack distribution of quasi-phase-matched materials on nonlinear frequency generation

    Page(s): 1560 - 1569
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    Analytical results indicate that the plate-thickness tolerance of the GaAs plates in a quasi-phase-matched (QPM) stack with respect to the coherence length is not a critical parameter. Rather, proper placement order of the plates of different thicknesses that make up the stack is essential for generating efficient nonlinear conversion; conversion efficiency approaching that from a stack of plates with plate thickness equal exactly to the coherence length can be obtained. In effect, such ordered stacking optimizes the relative phase of the nonlinear process as it propagates down the stack and enhances the conversion efficiency. Furthermore, the analysis shows that random-order stacking of plates of different thicknesses produces a large variation in conversion efficiency, varying from one random stack to another. This may not be desirable in practice; one would normally prefer to have a process that produces QPM stacks with good and predictable performance. A single-pass three-wave coupled nonlinear frequency interaction model with temporal and spatial pulse profiles is used to analyze the behavior of the nonlinear conversion process in a quasi-phase-matched stack. Second-harmonic generation of CO2 laser radiation in GaAs plates is used as an example View full abstract»

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  • Dynamic behavior of reflection optical bistability in a nonlinear fiber ring resonator

    Page(s): 1537 - 1543
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    We present an analysis of the dynamic behavior of a nonlinear fiber ring resonator when an optical pulse with an arbitrary shape envelope is incident into it through a fiber directional coupler. The transient analysis is based on the extension of a well-known multiple-beam interference method to non-linear transmission problems. The steady-state analyses reported so far predict that the ring resonator exhibits reflection optical bistability in the input-output characteristics under appropriate conditions. But, our transient analysis shows that a nearly periodical oscillation of the transmitted power always takes place at a suitable initial detuning when the resonator has no loss or a small loss. It seems that the present instability is caused by the repetition of accumulation and release of the power in the ring resonator. We can obtain a bistable hysteresis loop by introducing a loss to the directional coupler. The dynamic behavior of bistability in a nonlinear fiber ring resonator with coupler loss is then investigated. It is found that a remarkable undershoot and overshoot occur in the switch-off curve and switch-on curve, respectively View full abstract»

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  • Ti:Er:LiNbO3 waveguide laser of optimized efficiency

    Page(s): 1695 - 1706
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    The development of a Fabry-Perot-type Ti,Er:LiNbO3 waveguide laser of optimized CW output power up to 63 mW (λs =1561 nm) at a pump power level of 210 mW (λp=1480 nm) and a slope efficiency of up to 37% is reported. The theoretical model for the waveguide laser is presented and applied to determine the optimum resonator configuration using waveguide parameters obtained from a detailed characterization of the laser sample. With pulsed pumping, waveguide laser pulses of up to 6.2 W peak power were observed. Apart from residual relaxation oscillations, the laser emission proved to be shot-noise limited View full abstract»

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  • Tunneling injection lasers: a new class of lasers with reduced hot carrier effects

    Page(s): 1620 - 1629
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    In conventional quantum-well lasers, carriers are injected into the quantum wells with quite high energies. We have investigated quantum-well lasers in which electrons are injected into the quantum-well ground state through tunneling. The tunneling injection lasers are shown to have negligible gain compression, superior high-temperature performance, lower Auger recombination and wavelength chirp, and better modulation characteristics when compared to conventional lasers. The underlying physical principles behind the superior performance are also explored, and calculations and measurements of relaxation times in quantum wells have been made. Experimental results are presented for lasers made with a variety of material systems, InGaAs-GaAs-AlGaAs, InGaAs-GaAs-InGaAsP-InGaP, and InGaAs-InGaAsP-InP, for different applications. Both single quantum-well and multiple quantum-well tunneling injection lasers are demonstrated View full abstract»

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  • Optimization of an Er-doped silica glass optical waveguide amplifier

    Page(s): 1680 - 1684
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    The optical gain performance of a highly Er-doped waveguide amplifier is affected by concentration quenching and cooperative upconversion effects. Based on materials parameters, which were previously determined for Er-doped sodalime-silicate glass, we calculate how the gain performance can be improved by reducing these limiting processes. For amplifiers with an Er concentration exceeding 0.1 at.%, the Er dc-excitation rate is dominated by cooperative upconversion rather than radiative decay or nonradiative decay due to coupling to defects. The effect of lowering the waveguide loss and reducing the optical mode diameter is also demonstrated View full abstract»

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  • Multiple-route current-voltage (I-V) characteristics of GaAs-InGaAs metal-insulator-semiconductor-like (MIS) structure for multiple-valued logic applications

    Page(s): 1615 - 1619
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    A new GaAs-InxGa1-xAs metal-insulator-semiconductor-like (MIS) device with the interesting dual-route and multiple-negative-differential-resistance (MNDR) current-voltage (I-V) characteristics has been fabricated and demonstrated. These performances are caused by the successive barrier lowering and potential redistribution effect. A novel multiple-route I-V characteristic is obtained in the studied device at low temperature (-130°C). This performance is different from the previously reported NDR switching device and has not yet been found in other devices. The interesting property of the studied structure provides a promising candidate for switching device applications View full abstract»

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  • Numerical physics of subpicosecond electrical pulse generation by nonuniform gap illumination

    Page(s): 1672 - 1679
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    The physical mechanism of subpicosecond electrical pulse generated by nonuniform illumination of transmission-line gaps is studied in detail using a two-dimensional numerical model. This model agrees very well with existing theories as well as experimental observations and further explains the observed highly nonuniform field distributions, which have been neglected in previous theories. The pulse dependence on light intensity, bias voltage, substrate doping, and beam size and location are studied and discussed. It also confirms that this mechanism should be observable in silicon View full abstract»

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Aims & Scope

The IEEE Journal of Quantum Electronics is dedicated to the publication of manuscripts reporting novel experimental or theoretical results in the broad field of the science and technology of quantum electronics..

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Aaron R. Hawkins
Brigham Young University