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Quantum Electronics, IEEE Journal of

Issue 6 • Date June 2007

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Displaying Results 1 - 16 of 16
  • Table of contents

    Page(s): 435 - 436
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  • Output Phase Characteristics of a Nonlinear Regenerative Fiber Amplifier

    Page(s): 437 - 439
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (90 KB) |  | HTML iconHTML  

    A simple regenerative fiber amplifier with a nonlinear refractive index is described and analyzed. Using standard equations of operation, we model the circulating intensity within the resonant cavity and determine the nonlinear phase response to changes in this intensity over the entire range of initial cavity detuning. Simple stability criteria are established and described. It is shown that the presence of sufficient nonlinearity leads to stable regions of operation with consistent phase-intensity relationships. Based on these results, the phase of the amplifier output is predicted relative to the injected field for the entire range of initial detuning View full abstract»

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  • Equilateral-Triangle-Resonator Injection Lasers With Directional Emission

    Page(s): 440 - 444
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    Equilateral-triangle-resonator (ETR) lasers with an output waveguide jointed at one vertex of the resonator are fabricated on (100) GaInAsP-InP wafers using photolithography and a two-step inductively coupled plasma (ICP) etching technique. Distinct peaks with the mode spacing of longitudinal mode intervals are observed in the luminescence spectra at room temperature. Furthermore, some minor peaks appear in the middle of the main peaks, which can be attributed to the first-order transverse modes as predicted in the theoretical results. CW directional lasing emissions are achieved for ETR lasers with side lengths ranging from 15 to 30 mum up to 200 K. The temperature dependences of the threshold current and lasing wavelength are measured for an ETR laser with the side length of 20 mum from 80 to 200 K. The observed threshold current rapidly increases as temperature increases over 170 K View full abstract»

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  • Novel Gain Medium Design for Short-Wavelength Vertical-External-Cavity Surface-Emitting Laser

    Page(s): 445 - 450
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    We report on a novel material developed as the gain medium for a vertical-external-cavity surface-emitting laser (VECSEL) operating around 850 nm. The new material departs from the conventional approach of using GaAs as the quantum-well (QW) material and expands the previously reported concept of using InAlGaAs QWs. The inclusion of indium pins dislocation propagation into the active region of the VECSEL. Crucial for the success of this design is also the development of indium and phosphorous containing quinternary strain-compensating layers. These surround the QWs and provide a more substantial resistance to defect propagation. Results are presented for stable high-power single spatial mode operation of a laser based on this material together with measurements of the unsaturated gain of the device and the characteristic temperature for the threshold power View full abstract»

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  • Faraday Rotators With Short Magneto-Optical Elements for 50-kW Laser Power

    Page(s): 451 - 457
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    Faraday rotators with short magneto-optical elements are created and experimentally studied. The magneto-optical elements are made three to four times shorter either by cooling them to nitrogen temperatures or by increasing the magnetic field. These ways are shown to increase maximum average laser power passing through the Faraday isolators up to 50 kW View full abstract»

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  • Sudden Change of Electrical Characteristics at Lasing Threshold of a Semiconductor Laser

    Page(s): 458 - 461
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    Accurate forward electrical characteristics of multiquantum-well (MQW) lasers have been measured using ac admittance measurements together with dc I-V plot. The synchronous step offsets of apparent conductance, apparent capacitance, junction voltage, series resistance, and ideality factor at the onset of lasing were observed for the first time. With this effect, the lasing threshold can be deduced immediately by the LCR Meter. It is also found that the junction voltage jumps abruptly to a saturated value at the onset of lasing, and the starting and end points of jumping exactly correspond to the maximum of the second derivative of lasing power with respect to current and the kink point of the first derivative, respectively. All of the phenomena may help to verify and improve existing semiconductor laser models. In addition, negative capacitance effect in LDs was observed View full abstract»

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  • Three-Dimensional FDTD Simulation of Micro-Pillar Microcavity Geometries Suitable for Efficient Single-Photon Sources

    Page(s): 462 - 472
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    We present the results of calculations of the microcavity mode structure of distributed-Bragg-reflector (DBR) micro-pillar microcavities of group III-V semiconductor materials. These structures are suitable for making single photon sources when a single quantum dot is located at the center of a wavelength scale cavity. The 3-D finite difference time domain (FDTD) method is our primary simulation tool and results are validated against semi-analytic models. We show that high light extraction efficiencies can be achieved (>90%) limited by sidewall scattering and leakage. Using radial trench DBR microcavities or 2-D photonic crystal structures, we can further suppress sidewall emission, however, light is then redirected into other leaky modes View full abstract»

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  • Ultrafast Response of Arrayed Waveguide Gratings

    Page(s): 473 - 478
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    The ultrafast limit of the response of arrayed waveguide gratings is studied both theoretically and experimentally. We present new experimental results that show that interference occurs inside of an arrayed waveguide pulse shaper even when pulses that travel through different paths do not overlap. A comprehensive discussion of this extreme case is presented View full abstract»

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  • Metal–Dielectric Slot-Waveguide Structures for the Propagation of Surface Plasmon Polaritons at 1.55 μm

    Page(s): 479 - 485
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    We present a deep-subwavelength-size metal slot-waveguide structure which can efficiently propagate surface plasmon polaritons (SPPs) at 1.55 mum within a high-index material. Through a systematic design analysis, we investigate the intrinsic tradeoffs and suggest solutions to substantially increase the propagation length of SPPs combining high-index dielectrics and metal structures. By studying several metal/dielectric geometries, we have found that the slot-waveguide size can be significantly decreased by the use of high-index materials without compromising the overall propagation losses. Our analysis also indicates that the device size-scaling is ultimately limited by a cutoff thickness for the metal film in which the slot is defined. For film thicknesses below cutoff, radiation modes exist which leak out of the guiding region. For certain operating frequencies, the radiant energy leaks out into both free space modes as well as surface plasmons guided along the top/bottom metal surfaces of the device. We have shown that, by using a silicon filling, the cutoff thickness of a 100-nm-wide slot waveguide can be as small as 90 nm, compared with 750 nm for the unfilled reference structures. In addition, we have demonstrated that by the use of SiO2 gap regions surrounding the Si dielectric core in a 200times400-nm silver slot region (partially filled metal slot), we can considerably reduce the overall propagation losses to less than 0.14 dB/mum, corresponding to a propagation length of approximately 50 mum View full abstract»

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  • Ultrafast Electronic Dynamics in Unipolar n-Doped InGaAs–GaAs Self-Assembled Quantum Dots

    Page(s): 486 - 496
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    The dynamics of electron capture and relaxation in an n-doped quantum-dot (QD) infrared detector structure are studied directly in the time domain using ultrafast intraband-pump-interband-probe differential transmission spectroscopy. Femtosecond midinfrared pulses are used to excite electrons from the doped QDs into the conduction band continuum, and the complete electron distribution functions are monitored as a function of time using an interband probe. Because only electrons are excited and no holes are present, the electron-hole scattering which dominates the relaxation in bipolar systems is not present, and the measurement yields the electron dynamics exclusively. Excitation-dependent electron capture times were measured from 40 to <10 ps with increasing pump intensity. Intradot inter-level relaxation times were observed to be ~100 ps, driven by Auger-type electron-electron scattering. Nanosecond-scale dynamics in the n=1 state were also observed and attributed to transport effects. Our results indicate that the phonon bottleneck in the QDs is circumvented by Auger scattering; nevertheless, the electron dynamics in the unipolar device are found to be slower than those observed in bipolar systems, which confirms the significance of the holes in the carrier relaxation in bipolar devices. The results also support the improved operation of QD infrared photodetectors relative to quantum-well-based devices View full abstract»

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  • Mode Analysis and Q-Factor Enhancement Due to Mode Coupling in Rectangular Resonators

    Page(s): 497 - 502
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    Modes in rectangular resonators are analyzed and classified according to symmetry properties, and quality factor (Q-factor) enhancement due to mode coupling is observed. In the analysis, mode numbers p and q are used to denote the number of wave nodes in the direction of two orthogonal sides. The even and odd mode numbers correspond to symmetric and antisymmetric field distribution relative to the midlines of sides, respectively. Thus, the modes in a rectangle resonator can be divided into four classes according to the parity of p and q. Mode coupling between modes of different classes is forbidden; however, anti-crossing mode coupling between the modes in the same class exists and results in new modes due to the combination of the coupled modes. One of the combined modes has very low power loss and high Q-factor based on far-field emission of the analytical field distribution, which agrees well with the numerical results of the finite-difference time-domain (FDTD) simulation. Both the analytical and FDTD results show that the Q-factors of the high Q-factor combined modes are over one order larger than those of the original modes. Furthermore, the general condition required to achieve high-Q modes in the rectangular resonator is given based on the analytical solution View full abstract»

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  • Excess Avalanche Noise in In0.52Al0.48As

    Page(s): 503 - 507
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    Avalanche multiplication and excess noise arising from both electron and hole injection have been measured on a series of In0.52Al0.48As p+-i-n+ and n +-i-p+ diodes with nominal avalanche region widths between 0.1 and 2.5 mum. With pure electron injection, low excess noise was measured at values corresponding to effective k=beta/alpha between 0.15 and 0.25 for all widths. Enabled ionization coefficients were deduced using a non-local ionization model utilizing recurrence equation techniques covering an electric field range from approximately 200 kV/cm to 1 MV/cm View full abstract»

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  • Power Equalization for SOA-Based Dual-Loop Optical Buffer by Optical Control Pulse Optimization

    Page(s): 508 - 516
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    In this paper, a theoretical study and experimental demonstration are applied to achieve power equalization for semiconductor optical amplifier (SOA)-based dual-loop optical buffers (DLOBs). It is found that, due to the gain saturation and limited linewidth-enhancement factor of the SOA, the peak power of a packet pulse with an optically controlled delay of 9.9 mus is 4.83 dB lower than that of a packet pulse without storage. In order to eliminate the 4.83-dB output power fluctuation of the DLOB, a simple power-equalization method based on the optimization of an optical control pulse is proposed. By injecting a negative optical control pulse, the output power fluctuation of a packet pulse can be effectively reduced to zero. We have also investigated the peak power level of the optical control pulse required to fulfil the buffer function. It is found that the SOA with larger linewidth-enhancement factor and larger small-signal gain should be used to reduce the peak power of the optical control pulse. It is also theoretically found that, due to the negative optical-control pulse injection, the packet signal with Gaussian profile has some distortion after storage. However, the distortion effect is mitigated when the shape of the input pulse is more similar to the square profile. Finally, the proposed method for achieving power equalization in an SOA-based optical buffer has been justified by carrying out a 2.5-Gb/s 2times2 exchange-bypass optical switch experiment. We believe that this power-equalization method can be also applied to other SOA cross-phase modulation-based applications View full abstract»

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  • IEEE Journal of Quantum Electronics publication information

    Page(s): 517
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    Freely Available from IEEE
  • IEEE Journal of Quantum Electronics information for authors

    Page(s): 518
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    Freely Available from IEEE
  • [Front cover]

    Page(s): 519
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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