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Quantum Electronics, IEEE Journal of

Issue 10 • Date Oct 2001

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Displaying Results 1 - 17 of 17
  • Analysis of a dynamical procedure on diode-end-pumped solid-state lasers

    Page(s): 1368 - 1372
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    For solid-state lasers, we have determined that the overlap integrals Vth, related to the threshold pump power, and Vslope, related to the laser slope efficiency, dynamically change with pump power. The increase of diffraction loss is also caused by the dynamical change of the laser mode size, which alters the Fresnel number of the cavity. Subsequently, the threshold pump power and the laser slope efficiency also change dynamically. The dramatic increase of the laser mode radius at the laser crystal and the sudden decrease of the laser mode radius at the output mirror when operating near the stability limit make the laser output suddenly drop. A longer cavity will have a larger threshold pump power and a smaller total output power View full abstract»

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  • High-speed mid-IR modulator using Stark shift in step quantum wells

    Page(s): 1273 - 1282
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    We show in calculations that there is a capability for high speeds with a low applied voltage in modulators based on intersubband transitions in step quantum wells (QWs). A waveguide based on surface plasmons is assumed to achieve the necessary tight confinement of the optical field. In a structure with 8 GaInAs-AlGaInAs-AlInAs step QWs, we obtain a device capacitance of 14 fF corresponding to a RC limitation of electrical f3 dB=190 GHz. The extinction ratio of 6.6-μm light is 10 dB at an applied voltage of 0.9 V and T=300 K. By simple reasoning, we find that the device capacitance is approximately proportional to the absorption linewidth cubed when the linewidth is considered in the device design. Thus, the linewidth is very decisive for the modulation speed. We propose to place the dopants asymmetrically in the barriers in order to reduce broadening caused by doping induced potential fluctuations. In addition, the doping levels in the outermost barriers of the multi-QW structure are proposed to be reduced and asymmetrical, in order to achieve a uniform electric field over the step QWs, which is shown to increase the achievable f3 dB very markedly View full abstract»

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  • Proposal and finite-difference time-domain simulation of whispering gallery mode microgear cavity

    Page(s): 1253 - 1258
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    The existence of many high Q whispering gallery modes in microdisk and microcylinder lasers seriously affects the internal efficiency in lasing operation and disturbs the enhancement of the spontaneous emission factor. To suppress these modes except for one lasing mode, we propose the microgear cavity having a grating with the same period as that of the mode standing wave. A finite-difference time-domain simulation theoretically demonstrates that the microgear selects one resonant mode that satisfies the unique condition regarding the mode order and the phase. This paper describes the dependence of the mode behavior on some structural parameters, and concludes that a deep grating, which seems to be possible in an experiment, allows for sufficient suppression of any types of nonlasing modes and the enhancement of the Q factor of the lasing mode View full abstract»

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  • High-speed modulation of long-wavelength In1-xGax AsyP1-y and In1-x-yGaxAlyAs strained quantum-well lasers

    Page(s): 1283 - 1291
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    In1-xGaxAs1-yPy quantum-well (QW) lasers with compressive strain and In1-x-yGaxAlyAs QW lasers with two strain types (compressively strained and lattice matched) for 1.55-μm telecommunication applications are investigated both in the steady-state and high-speed microwave modulation schemes. Under steady-state electric bias, the gain and intrinsic loss are measured based on the well-known Hakki-Paoli method from below threshold to threshold. The photon lifetime is obtained from this measurement. A comprehensive theoretical gain model with realistic band structure, including valence band mixing and many-body effects, is then used to fit the experimentally obtained modal gain profiles and extract the carrier density and, therefore, the differential gain. In the high-speed microwave modulation scheme, the experimental modulation response curves are fitted by the theory and parameters such as the differential gain and K factor are obtained. The differential gain agrees very well with the value obtained from the steady-state direct optical gain measurement. The comparison of two material systems will be important to design high-bandwidth high-performance semiconductor lasers in order to meet requirements of 1.55-μm telecommunication applications View full abstract»

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  • Green single- and two-photon gap emission of thin-film CdS formed by infrared pulsed-laser deposition on glass

    Page(s): 1363 - 1367
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (87 KB) |  | HTML iconHTML  

    Thin-film CdS is formed by infrared pulsed-laser deposition (PLD) on glass. The film is excited with continuous-wave (CW) blue laser emission at 457.9 nm and with ultra-fast laser pulses of 200 fs at 801 nm. Both excitations cause green gap emission in the range from 2.43 to 2.45 eV at room temperature. Additionally, blue excitation evokes some sub-gap emission. The principle of detailed balance is used to describe the shape of the two-photon spectrum by modeling the absorption coefficient by the density of states and Urbach's rule. Spectra measured through the glass substrate are shifted 40 meV to lower energies with respect to the emission emitted from the front side of the film. Using Beer's law, it is shown that the shift is caused by stronger absorption at the glass/CdS interface. This is confirmed with the lack of geometry dependence of an interface-free 50-μm CdS platelet. The results show that two-photon spectroscopy is useful for revealing the interfacial absorption effects and PLD CdS exhibits outstanding emission properties, which are important for green light-emitting device fabrication View full abstract»

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  • Dynamic analysis of multiple wavelength DFB fiber lasers

    Page(s): 1237 - 1245
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    The behavior of multi- and single-wavelength distributed feedback fiber lasers is simulated in a comprehensive dynamic model. The evolution of the spatial distribution of gain, saturation-induced gain gratings, and spontaneous emission is taken into account. Stability and relative intensity noise (RIN) of the different laser types and laser modes are compared, and the effect of varying degree of pump RIN and quenching of spontaneous emission lifetimes is analyzed View full abstract»

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  • Synchronization and communication using semiconductor lasers with optoelectronic feedback

    Page(s): 1301 - 1311
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    Semiconductor lasers provide an excellent opportunity for communication using chaotic waveforms. We discuss the characteristics and the synchronization of two semiconductor lasers with optoelectronic feedback. The systems exhibit broadband chaotic intensity oscillations whose dynamical dimension generally increases with the time delay in the feedback loop. We explore the robustness of this synchronization with parameter mismatch in the lasers, with mismatch in the optoelectronic feedback delay, and with the strength of the coupling between the systems. Synchronization is robust to mismatches between the intrinsic parameters of the lasers, but it is sensitive to mismatches of the time delay in the transmitter and receiver feedback loops. An open-loop receiver configuration is suggested, eliminating feedback delay mismatch issues. Communication strategies for arbitrary amplitude of modulation onto the chaotic signals are discussed, and the bit-error rate for one such scheme is evaluated as a function of noise in the optical channel View full abstract»

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  • Non-evanescent adiabatic directional coupler

    Page(s): 1321 - 1328
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    A directional coupling mechanism based on an adiabatic coupling between three optical modes is suggested. The optical power transfer between two waveguides which are far apart is mediated by adiabatic coupling between zero-order optical modes of the individual waveguides and a high-order intermediate mode. The analytical model for an adiabatic three-mode coupling based on a scalar wave equation is presented. The directional coupling via the adiabatic mode coupling between copropagating modes is described and compared with a nonadiabatic directional coupling assisted by periodic perturbation. It is shown that adiabatic directional coupling has much less sensitivity to the mode parameters and to the wavelength View full abstract»

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  • Monolithic InGaAsP optoelectronic devices with silicon electronics

    Page(s): 1246 - 1252
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB) |  | HTML iconHTML  

    The interface between optoelectronic devices and microelectronic circuits is the crucial component in the further development of optical communications, calling for inexpensive mass-produced solutions. We present a procedure for how these diverse elements can be monolithically integrated. A stringent requirement is the compatibility with existing fabrication techniques of microelectronic circuits in silicon. We demonstrate the feasibility of our method by the monolithic integration of a photodetector, based on InGaAs-InP, with a three-stage MOS amplifier on a Si substrate in (100) crystallographic orientation. Basic performance figures (dark current, sensitivity) are comparable to those obtained with test structures on the native InP substrate. We show that the developed technologies can be extended to light-emitting diodes and laser structures displaying efficient electroluminescence View full abstract»

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  • Time-domain large-signal investigation on nonlinear interactions between an optical pulse and semiconductor waveguides

    Page(s): 1329 - 1336
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    A time-domain large-signal model is developed to investigate nonlinear interactions between picosecond optical pulses and semiconductor active waveguide devices, including distributed-feedback and Fabry-Perot lasers, as well as optical amplifiers. The model predicts interesting phenomena such as transform-limited superluminal transmission and directional DFB amplification. The influence of electrical carrier dynamics and feedback from a Bragg grating and/or reflecting facets on output pulses are demonstrated. Moreover, it is found that the time delay of the reflected and transmitted pulses is strongly related to the Bragg grating parameters, as well as to carrier dynamics. As a consequence, careful attention should be paid when the notions of group refractive index and group velocity are to be used in device modeling View full abstract»

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  • Gain optimization in optically pumped AlGaAs unipolar quantum-well lasers

    Page(s): 1337 - 1344
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    A method is described for the optimized design of quantum-well (QW) structures, in respect to maximizing the stimulated gain in optically pumped intersubband lasers. It relies on applying supersymmetric quantum mechanics (SUSYQM) to an initial Hamiltonian, in order to both map one bound state below the spectral range of the initial Hamiltonian, and to generate a parameter-controlled family of isospectral Hamiltonians with the desired energy spectrum. By varying the control parameter, one changes the potential shape and, thus, the values of dipole matrix elements and electron-phonon scattering matrix elements. The use of this procedure is demonstrated by designing smoothly graded and stepwise-constant AlxGa1-xAs ternary alloy QWs, with the self-consistent potential taken into account. Finally, the possibility of employing layer interdiffusion to get optimal smooth potentials is discussed View full abstract»

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  • Active mode locking with hybrid lasers

    Page(s): 1265 - 1272
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    We present the results of a numerical study of active mode locking with hybrid lasers which contain an inhomogeneously broadened laser medium and an homogeneously broadened laser medium. The spectral, pulse, and gain characteristics of actively mode-locked hybrid lasers and the influence of the unsaturated gain, the saturation power, and the homogeneous linewidth on the pulse coherence and bandwidth are studied. The simulations show that coherent and shorter pulses are generated as compared to that by either an inhomogeneously broadened medium or a homogeneously broadened medium alone. Varying the unsaturated gain or the saturation power of the gain medium are two equivalent ways to obtain the same maximal coherent pulse bandwidth for given gain media. When different gain media can be selected, a larger pulse bandwidth can be obtained with the use of a broadband homogeneously broadened medium View full abstract»

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  • Spatio-temporal dynamics of light amplification and amplified spontaneous emission in high-power tapered semiconductor laser amplifiers

    Page(s): 1345 - 1355
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    We investigate the spatio-temporal light field dynamics in high-power semiconductor lasers with continuous-wave optical injection. The amplification processes that characterize this system occur during the propagation of the injected signal within the active area and can be attributed to spatially dependent gain and refractive index variations. Those are shown to be determined by dynamic interactions between the light fields and the active charge-carrier plasma. This microscopic light-matter-coupling is described by a spatially resolved microscopic theory based on Maxwell-Bloch-Langevin equations taking into account many-body interactions, energy transfer between the carrier and phonon system and, in particular, the spatio-temporal interplay of stimulated and amplified spontaneous emission and noise. Results of our numerical modeling visualize the dynamic spatio-spectral beam shaping experienced by the propagating light in amplifiers of tapered geometry. This reveals the microscopic physical processes that are responsible for the particular amplitude and spatial shape of the light beam at the output facet View full abstract»

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  • Modeling the electrooptic evolution in thermally poled germanosilicate fibers

    Page(s): 1312 - 1320
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    We formulate a simple quantitative three-species charge-carrier transport model, consisting of two distinct positive ions and a single negative ion, to describe the dynamics during thermal poling of a germanosilicate optical fiber. We numerically solved the equations and report one-dimensional space-time solutions for the electrooptic (EO) coefficient. In the two-cation model, our findings show the EO coefficient initially dips near the anode and then monotonically rises to a steady-state value, higher than that produced by the initial applied poling field. However, at the cathode, the electric field quickly dropped to zero where it remained zero for the poling duration. The introduction of a moving negative ion clearly shows the existence of a dead time characteristic appearing at the cathode, resulting in a gain in the initial EO coefficient. This model also reveals that the resulting EO evolution in a thermally poled germanium-boron codoped fiber can he attributed to the movement of just two ions of opposite polarity. To explain the increase in the EO coefficient in boron codoped germanosilicate fiber, we found it necessary to allow for an increase in the third-order susceptibility by a factor of ~3.4 View full abstract»

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  • A dual-color injection laser based on intra- and inter-band carrier transitions in semiconductor quantum wells or quantum dots

    Page(s): 1356 - 1362
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    A new type of semiconductor injection laser capable of simultaneously generating radiation in the mid-infrared (MIR) (λ~10 μm) and near-infrared (NIR) (λ~0.9 μm) spectral regions is proposed. The MIR emission is a result of intersubband (intraband) electron transitions within a three-level conduction band in a quantum well or a quantum dot. The NIR emission, on the other hand, is due to conventional interband recombination of injected electrons and holes into the conduction and valence bands, respectively. The conditions for population inversion in the intersubband emission process are determined by an appropriately engineered energy structure for a three-level system in the conduction band of a quantum well or dot structure: for the quantum-well-based system, the structure has an asymmetric funnel shape to provide long electron-phonon lifetime at the third (top) energy level. Under high carrier injection, NIR interband emission depopulates the conduction ground level of the quantum well, thereby stabilizing the electron concentration at this level-a necessary condition fur the operation of the MIR laser. This paper discusses the calculation of the population inversion conditions, the requisite gain, and threshold current for MIR laser operation. We also present a preliminary design of the laser structure with a composite waveguide that accommodates both mid- and NIR stimulated emission View full abstract»

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  • Analysis of semiconductor microlasers with an equilateral triangle resonator by rate equations

    Page(s): 1259 - 1264
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    Semiconductor microlasers with an equilateral triangle resonator (ETR) are analyzed by rate equations with the mode lifetimes calculated by the finite-difference time-domain technique and the Pade approximation. A gain spectrum based on the relation of the gain spectrum and the spontaneous emission spectrum is proposed for considering the mode selection in a wide wavelength span. For an ETR microlaser with a side length of about 5 μm, we find that single fundamental mode operation at about 1.55 μm can be obtained as the side length increases from 4.75 to 5.05 μm. The corresponding wavelength tuning range is 93 nm, and the threshold current is about 0.1 to 0.4 mA View full abstract»

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  • Characteristics of second-harmonic generation including third-order nonlinear interactions

    Page(s): 1292 - 1300
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    A theoretical analysis is presented for second-harmonic generation in nonlinear dielectric media. Mathematical expressions are derived for both the amplitude and phase evolution of optical waves for second-harmonic generation, wherein both second- and third-order nonlinear interactions are taken into consideration. Based on the results, numerical examples of second-harmonic generation in LiNbO3 are presented, and the effects of third-order interactions on the frequency conversion efficiency and the intensity-dependent phase-matching condition are discussed. The derived result is amenable to a rigorous analysis of second-harmonic generation with a high-intensity incidence to nonlinear dielectric media, where the intensity-dependent optical parameters cannot he neglected 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..

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Meet Our Editors

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