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Quantum Electronics, IEEE Journal of

Issue 3 • Date March 2000

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Displaying Results 1 - 18 of 18
  • Above-threshold analysis of second-order circular-grating DFB lasers

    Page(s): 259 - 267
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    The behavior of second-order circular-grating DFB lasers in the above-threshold regime are analyzed. The formulation uses the standing wave method for treating lasers with second-order gratings. The effects of spontaneous emission and the variation of carrier and photon densities in the radial direction are included in a self-consistent fashion in the model. In particular, we examine the output power emitted from the surface of the laser, the near-field, and the far-field pattern of the laser as a function of the injected current. View full abstract»

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  • Novel all-reflective stretcher for chirped-pulse amplification of ultrashort pulses

    Page(s): 268 - 274
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    We describe the design and operation of an all-reflective on-axis pulse stretcher (with only four simple elements) that has achieved stretching ratios of over 40000. The design is insensitive to alignment errors and is simple to align. Optical aberrations in the system have an effect on the fourth-order phase term, but this can be used to compensate for material dispersion, resulting in a quintic-phase-limited chirped-pulse-amplification system. View full abstract»

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  • Nonlinear harmonic generation in free-electron lasers

    Page(s): 275 - 281
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    A three-dimensional nonlinear simulation code to treat multiple frequencies simultaneously is described and used to study nonlinear harmonic generation in free-electron lasers (FELs). Strong nonlinear harmonic gain is found where the gain length varies inversely with the harmonic number. Substantial power levels are found in the harmonics. The odd harmonics are favored with generally higher power levels since a planar wiggler geometry is employed; however, the second harmonic exhibits substantial power as well. The analysis is relevant to the emission expected from self-amplified spontaneous emission (SASE) free-electron laser schemes. View full abstract»

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  • Finite-element analysis of second-harmonic generation in AlGaAs waveguides

    Page(s): 282 - 289
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    A rigorous and efficient finite-element method based beam propagation method is used to model second-harmonic generation (SHG) in semiconductor waveguides. The effect of loss on the efficiency of SHG is analyzed and it is shown that, under certain conditions, GaAlAs-based devices with a lower nonlinear susceptibility tensor could be more efficient than GaAs-based devices with a higher nonlinear susceptibility tensor. Numerical results are also presented, to show the effect of domain fabrication error, in the case of quasi-phase-matched devices, on the efficiency of SHG. View full abstract»

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  • "Magic" dispersion maps for multichannel soliton transmission

    Page(s): 290 - 299
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    Using asymptotic theory and a momentum method, we have identified a family of dispersion management schemes that are advantageous for massive multichannel soliton transmission. For the practical case of two-step dispersion maps, special schemes are found that have optimal launch point locations (where no pulse prechirping is needed) that are independent of the fiber's dispersion. Despite the variation of dispersion with respect to carrier wavelength due to the fiber's dispersion slope, the transmission in several different channels can be optimized simultaneously using the same optimal launch point. Theoretical predictions are verified by direct numerical simulations. View full abstract»

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  • A synchronization scheme using self-pulsating laser diodes in optical chaotic communication

    Page(s): 300 - 304
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    A synchronization scheme using self-pulsating laser diodes in optical chaotic communication is proposed. Optical chaotic light can be obtained by injecting a sinusoidal electronic signal into a self-pulsating laser diode. To synchronize between two identical chaotic systems with different initial conditions, a drive and response system model is constructed according to Pecora and Carroll's theory. Synchronization can be achieved for optical simplex and duplex transmissions provided that the conditional Lyapunov exponents for the drive and response systems are all negative. This approach offers a key step toward realizing optical chaotic modulation and demodulation. View full abstract»

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  • Optical frequency domain ranging by a frequency-shifted feedback laser

    Page(s): 305 - 316
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    This paper describes the theoretical and experimental study of a new technique for optical frequency domain ranging (OFDR) by a frequency-shifted feedback (FSF) laser. In conventional OFDR, a frequency chirped single-mode laser is used as a light source to convert a distance into a beat frequency, and a tradeoff exists between measurement range and resolution. The FSF laser output consists of periodically generated chirped frequency components whose chirp rate is faster than 100 PHz/s (P=10/sup 15/), By use of the FSF laser, the tradeoff is removed and long-distance high-resolution OFDR is realized In the experiment, a distance of 18.5 km was measured with a resolution of 20 mm. View full abstract»

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  • A chopped quantum-well polarization-independent interferometric switch at 1.53 /spl mu/m

    Page(s): 317 - 324
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    We have theoretically designed and realized a phase shifter for a low-loss Mach-Zehnder interferometric switch. The phase shifter is based on 0.85% tensile strained InGaAs-InP chopped quantum-well material. We realized a Mach-Zehnder interferometric switch with polarization-independent switching voltages as low as 3.3/spl plusmn/0.05 V at 1525 nm for a switch with a 4-mm-long phase shifting section. The wavelength sensitivity of the switch is 0.036 V/nm for TE and 0.053 V/nm for TM polarization. Calculations of the electro-refraction in the -0.85% strained chopped quantum-well (QW) material based on the 4/spl times/4 Luttinger-Kohn Hamiltonian show that the electro-refraction due to the quantum-confined Stark effect (QCSE) for TM polarization is equal to the sum of the mutually comparable QCSE electro-refraction and the Pockels effect for TE polarization in waveguides along the [11~0] axis. Our first-principle model for calculating the electro refraction is an accurate design tool for predicting device performance in complicated layer structures. The shortest possible phase shifter with a <-25 dB crosstalk penalty due to electro-absorption unbalance can be as short as 2.2 mm. This compact switch is predicted to have a 6-V switching voltage and a 15-nm window for polarization-independent switching with a <-25-dB crosstalk penalty. With a slight increase of the strain, this chopped QW material can be used for polarization independent switching around 1550 nm. View full abstract»

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  • Design of resonant-cavity-enhanced photodetectors using genetic algorithms

    Page(s): 325 - 332
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    Expressions of quantum efficiency of resonant-cavity-enhanced (RCE) PIN photodetectors reported in the literature are based on the assumption of constant reflectivities of the quarter-wave stacks (QWS) at the ends of the cavity. The quantum efficiency is formulated in a closed analytical form that includes the structural parameters of the photodetector and takes into account the wavelength dependence of the reflectivities and the active region absorption coefficient. The variation of the QWS reflectivity and, in particular, its phase constant with wavelength has a significant influence on the resulting quantum efficiency spectra, as demonstrated in this paper. The results are in very good agreement with recently published experimental data which show a dominant peak at the operating wavelength. This behavior has not been predicted by previous simulation results. Since the quantum efficiency spectra are not periodic, the use of the finesse, defined as the ratio of the free spectral range to the full width at half maximum, as a measure of wavelength selectivity is not valid. The conventional quality factor definition used for filter design is thus adopted as a measure of selectivity. A genetic algorithm-based optimization and design procedure for RCE photodetectors have also been developed with the quantum efficiency, quality factor, and frequency bandwidth as input design parameters. View full abstract»

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  • Effectiveness of the pseudowindow for edge-coupled InP-InGaAs-InP PIN photodiodes

    Page(s): 333 - 339
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (177 KB)  

    We have shown that edge-coupled PIN photodiodes can benefit from the incorporation of a pseudowindow of appropriate thickness. In our experiments, a pseudowindow 2-3 /spl mu/m thick can effectively protect the device and antireflection (AR) coating during the cleavage process without sacrificing the device efficiency and speed performance. Also, devices with a pseudowindow could have an increased coupling aperture, which results from the dielectric layers, and thus permits more light to enter the device. The light input facet of the device without a pseudowindow can be severely damaged during the cleavage process and AR coating, which may degrade the device dark current by several orders of magnitude. We also found that, even with partial recovery after rapid thermal annealing, devices without pseudowindows still suffer from damage and the maximum photocurrent is typically restricted to about 3 mA. The typical performance at -5 V of a device with a 100-/spl mu/m junction length and a 3-/spl mu/m pseudowindow is a responsivity of /spl sim/0.95 A/W responsivity and a /spl sim/5.5-GHz bandwidth at a wavelength of 1.3 /spl mu/m under 100-/spl mu/W illumination. View full abstract»

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  • An autocompensating fiber-optic quantum cryptography system based on polarization splitting of light

    Page(s): 340 - 347
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB)  

    We have developed a system for quantum key distribution (QKD), based on standard telecommunication lasers, detectors, and optical fiber, that passively compensates for time-dependent variations of the fiber-optic path due to stress, temperature changes, or birefringence. This approach allows information encoded in phase shifts imposed on single-photon-level pulses to be accurately read out after transmission over many kilometers of uncontrolled fiber. Cooled InGaAs avalanche photodiodes, pulse-biased using a special noise canceling circuit, are used to detect single 1.31-/spl mu/m infrared photons with a high efficiency, low dark-count rate, and subnanosecond time resolution. A single optical fiber carries both the quantum information and precise 1.55 /spl mu/m timing pulses between the two end stations. Overall synchronization of end-station activities, public discussion of basis choices, error correction, and privacy amplification have all been implemented over a local area network (LAN). The system at present generates raw, error-corrected, and privacy-amplified key data at rates of /spl sim/1000, 600, and 200 bits/s, respectively, over a 10-km single-mode fiber link. View full abstract»

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  • 2-D-3-D crossover in single asymmetric quantum wells: investigation of the electric field and temperature effects

    Page(s): 348 - 353
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    The 2-D-3-D crossover in n-doped GaAs-Ga/sub 0.63/Al/sub 0.37/As single asymmetric quantum wells is theoretically investigated. The coupled one-dimensional Schrodinger and Poisson equations are solved self-consistently, in the frame of the finite-difference method. The present study shows that the 2-D-3-D crossover depends upon the geometrical parameters, as for instance, the quantum well width and spacer layer width. It also depends on the temperature and the gate voltage applied on an asymmetric quantum-well-based device. The 2-D-3-D crossover diagrams involving the well width dependence of both the electric field and the temperature are presented and discussed. View full abstract»

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  • On the dimensionality of optical absorption, gain, and recombination in quantum-confined structures

    Page(s): 354 - 362
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    The purpose of this paper is to explore the dimensionality of the optoelectronic properties of quantum-well and dot systems by expressing carrier distributions in the confinement directions in terms of envelope functions rather than assuming that carriers are localized to the geometrical extent of the confining potential. The conclusions apply to an ideal two-dimensional (2-D) system or a structure where only the n=1 electron and hole subbands are populated. We show that optical absorption normal to the plane of a QW cannot be expressed as an absorption coefficient but should be specified as a fraction of light transmitted or absorbed per well. The modal gain for light propagating along the plane of a QW does not scale with well width and the variation of the material gain inversely proportional to the well width is a consequence of the definition of the confinement factor and has no independent physical significance. Coupling to the optical mode can be specified as a mode width without the need to assume the gain medium is localized in the well. Optical absorption and gain by quantum dots should be expressed as a cross section per dot. The radiative recombination current should be expressed in terms of a two-dimensional recombination coefficient and use of an equivalent three-dimensional coefficient introduces an artificial dependence on well width which can lead to errors in the comparison of QW systems. We provide an analysis of experimental data for optical absorption in GaAs wells and show that, using the correct dimensional forms, it is straightforward to use this to estimate modal gain and the recombination coefficient. View full abstract»

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  • Analytical solution for the eigenmodes of closed waveguide resonators with small curvature mirrors

    Page(s): 363 - 365
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    The exact closed-form expression of the eigenmodes of a closed waveguide resonator terminated with small-curvature cylindrical mirrors is presented. The results obtained are compared with those recently obtained through the use of the WKB approximation. Plots of the spatial structure of the transverse modes inside the resonator are also shown. View full abstract»

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  • Self-consistent analysis of high-temperature effects on strained-layer multiquantum-well InGaAsP-InP lasers

    Page(s): 366 - 374
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (214 KB)  

    We present a comprehensive evaluation of the temperature effects on the threshold current and the slope efficiency of 1.55 /spl mu/m Fabry-Perot ridge-waveguide lasers between 20/spl deg/C and 120/spl deg/C. Experimental results are analyzed using the commercial laser simulator PICS3D. The software self-consistently combines two-dimensional carrier transport, heat flux, strained quantum-well gain computation, and optical waveguiding with a longitudinal mode solver. All relevant physical mechanisms are considered, including their dependence on temperature and local carrier density. Careful adjustment of material parameters leads to an excellent agreement between simulation and measurements at all temperatures. At lower temperatures, Auger recombination controls the threshold current and the differential internal efficiency. At high temperatures, the vertical electron leakage from the separate confinement layer mainly limits the laser performance. The increase of internal absorption is less important. However, all these carrier and photon loss enhancements with higher temperature are mainly triggered by the reduction of the optical gain due to wider Fermi spreading of electrons. View full abstract»

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  • Experimental and theoretical study of filtered optical feedback in a semiconductor laser

    Page(s): 375 - 384
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (434 KB)  

    We report on the systematical investigation of the steady-state regime and the dynamical behavior of a semiconductor laser subject to delayed filtered optical feedback. We study a Fabry-Perot (FP) interferometer type of filter placed in the external feedback loop of a diode laser. The effects of the filter on the locking of the diode laser frequency to the external cavity modes are described. We report and observe hysteresis, bistability, and multistability and show that all these are well described by a set of rate equations for the coupled laser and FP cavity system. We also present an experimental stability diagram that summarizes the dynamical behavior of the system. View full abstract»

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  • Noise characteristics of single-mode semiconductor lasers under external light injection

    Page(s): 385 - 393
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    Presents a theoretical investigation of the noise behavior of a semiconductor laser operating under relatively strong light injection. Equations have been presented to describe the noise effect through the calculation of the relative intensity noise as well as the carrier-to-noise ratio available at the receiving end. Illustrative examples are given, showing the impact of the master and slave laser bias currents. Also, the injection-locked and free-running operation regimes have been comparatively analyzed. The results show how the noise characteristics are affected by optical injection and, consequently, how the operating conditions must be chosen to reduce this effect. In particular, it is shown, in agreement with previous works, that the master laser emission noise will essentially take the lead. As a result, to improve the noise behavior by injection locking a solitary laser, the use of a low-noise master laser is required. To make it easy to apply the present results to any laser diode under the stable-locking condition, the necessary relations are explicitly given before specifying the parameters of simulation. View full abstract»

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  • Supermode stabilized coupled-cavity 5- and 10-GHz mode-locked Ti:Er:LiNbO/sub 3/ waveguide lasers

    Page(s): 394 - 399
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    By coupling the active laser cavity to a passive low-finesse Fabry-Perot resonator, supermode stabilization of mode-locked Ti:Er:LiNbO/sub 3/ waveguide lasers for 5- and 10-GHz pulse repetition rates with side mode suppression ratios of 60 and 55 dB has been achieved. The 10-GHz source emits pulses with a pulsewidth of 5.7 ps and a time-bandwidth product lower than 0.52 within an RF frequency tuning range of 3.2 MHz. The 5-GHz source has been used in a 2/spl times/5 Gbit/s soliton transmitter. In a back-to-back measurement, a Q-factor of 25.1 dB has been obtained. In soliton transmission experiments over 160 km on a step-index fiber, an extrapolated bit error rate of 6/spl middot/10/sup -17/ has been measured. The passive cavity can serve also as a pulse repetition rate multiplier. Pulse repetition rate multiplication from 2.5 to 10 GHz has been demonstrated. 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