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Quantum Electronics, IEEE Journal of

Issue 5 • Date May 2005

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Displaying Results 1 - 25 of 25
  • Table of contents

    Page(s): c1 - c4
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  • IEEE Journal of Quantum Electronics publication information

    Page(s): c2
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  • Modal switching in quantum-well semiconductor lasers with weak optical feedback

    Page(s): 609 - 618
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1192 KB) |  | HTML iconHTML  

    We analyze theoretically and experimentally how the modal dynamics of quantum-well semiconductor lasers is affected by weak optical feedback. Without feedback, these lasers exhibit a regular switching among several longitudinal modes, following a well determined modal sequence and leaving the total intensity output constant. Using a multimode theoretical model we have identified the four wave mixing as the dominant mechanism at the origin of these intriguing dynamics, while the asymmetry of the susceptibility function of semiconductor materials allows to explain the modal sequence. In this manuscript we show that these dynamics, which is almost insensitive to current noise or modulation, is instead extremely sensitive to optical feedback. The experimental results are satisfactorily compared with the numerical predictions of the model, properly adapted for including weak optical feedback. View full abstract»

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  • Investigation of polarization bistability in vertical-cavity surface-emitting lasers subjected to optical feedback

    Page(s): 619 - 624
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    Polarization bistability in vertical-cavity surface-emitting lasers (VCSELs) subject to optical feedback has been studied both experimentally and theoretically. Optical feedback is shown to reduce the width of the bistability hysteresis loop and, hence, suppress the bistability. It is also demonstrated experimentally that polarization-selective optical feedback can be utilized to eliminate VCSEL polarization switching without inducing instabilities in the device. View full abstract»

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  • Influence of facet coating on the dual wavelength operation of asymmetric InGaAs-GaAs quantum-well lasers

    Page(s): 625 - 629
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    A low-reflectivity SiNyOz film was deposited on one facet of asymmetric In xGa1-xAs-GaAs quantum-well (QW) laser diodes containing three different QW compositions with the indium fractions x=0.25,0.21, and 0.15, located, respectively, from the n-doped to p-doped sides of the device. Lasing is only observed on the two higher In-content QWs. The reduction of the reflectivity of one facet, with the other as-cleaved, leads to an increase in the transition cavity length, below which the diode initially lases on the shorter wavelength QW (x=0.21) at threshold and above which the diode lases on the longer wavelength QW (x=0.25). No lasing occurs on the shortest wavelength QW (x=0.15). With sufficient current injection simultaneous lasing on the two QWs is observed. When dual-wavelength emission occurs the facet reflectivity determines whether the short or long wavelength emitting QW lases first as the pump current is increased. A separation of up to 31 nm between the two wavelengths is observed under the dual wavelength emission conditions. View full abstract»

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  • Comparison of facet temperature and degradation of unpumped and passivated facets of Al-free 940-nm lasers using photoluminescence

    Page(s): 630 - 635
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    Influences of facet degradation of Al-free InGaAsP-GaAs 940-nm laser diodes were studied at power densities well below catastrophic optical mirror damage level using photoluminescence (PL) during normal operation and after a rigorous burn-in procedure. The shift in the PL peak of the cladding layer of the device is used to calculate the temperature of the facet. Devices with different facet treatments: untreated electron beam evaporation, untreated ion beam deposition, unpumped and passivated facets were compared. The results indicate that the degradation of facet is more severe for untreated and unpumped facets as compared to passivated facets. The results were also compared with power measurements, which show that the drop in the power during the first 50 h of operation is nonexistent for passivated facet devices leading to the conclusion that photo-induced oxidation is the major cause of the degradation of the facet and thus oxide removal and surface passivation are crucial to make stable laser diodes. View full abstract»

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  • Numerical and theoretical analysis of the crosstalk in linear optical amplifiers

    Page(s): 636 - 641
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    The dynamic characteristics, including the crosstalk and relaxation oscillation, of linear optical amplifiers (LOAs) are investigated by small-signal analysis under an averaging carrier density approximation and compared with the results of numerical simulation. The good agreement between the numerical simulation and the small-signal analysis indicated the averaging carrier density is an appropriate approximation for analyzing LOAs. Theoretical analyzes also show that the dynamic properties of the vertical laser fields dominate the dynamic performance of LOAs. Based on the small-signal analysis, a concise equation for the crosstalk under high bit rate was derived, which can be applied to measure the differential gain of LOAs. View full abstract»

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  • Performance comparison of GaInNAs vertical-cavity semiconductor optical amplifiers

    Page(s): 642 - 649
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    This paper reports on theoretical and experimental investigations of the influence of the number of GaInNAs quantum wells (QWs) on performance of 1.3-μm vertical-cavity semiconductor optical amplifiers (VCSOAs). Full characterization is carried out for two optically pumped VCSOAs with 6 and 15 QWs in the active layer. The 15-QW amplifier is found to be more efficient for amplification purposes but the highest gain to date was obtained for a 6-QW GaInNAs VCSOA, 19-dB on-chip gain in single-mode operation, having a top mirror reflectivity of 97.7%. At high-gain and for low enough reflectivity, the intrinsic noise figure is smaller than 5 dB. View full abstract»

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  • Correlation of theory with experimental SOAs

    Page(s): 650 - 656
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    Predictions for the near-traveling wave amplifier (NTWA) with multiple-quantum-well structures have been developed. The continuity equation for quantum wells (QWs) with high carrier densities is combined with the amplifier TW gain equation expressed in terms of stimulated lifetime. This formulation allows the signal gain to be related to the bias current and the optical input signal through Fermi energies. The charge neutrality condition also plays an important role for high carrier density QW amplifiers. Auger recombination and heating effects are incorporated as essential components of the model. Experimental measurements of gain versus bias current and output power for both λ= 850- and 1550-nm devices are found to be very well matched by the calculated results. View full abstract»

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  • Analysis of tunable photonic crystal devices comprising liquid crystal materials as defects

    Page(s): 657 - 665
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    The tuning properties of two-dimensional dielectric and metallic photonic crystals, which contain nematic liquid crystal materials as defect elements or layers, are thoroughly analyzed using appropriate formulations of the finite difference time domain (FDTD) method. Our methodology correctly incorporates the anisotropy introduced by the liquid crystal materials together with the dispersive properties of the metallic elements; it is used for calculating both the dispersion diagrams of the defect-free photonic crystal as well as the device response in the presence of the defect elements. Numerical simulations reveal that defect states originating from the liquid crystal impurities can be effectively tuned by the application of a local static electric field. Indeed, tuning ranges up to almost 100 nm can be achieved requiring operating voltages lower than 4 V. It is also concluded that the placement of a defect mode relative to the bandgap edges greatly influences both its linewidth as well as its tuning range. View full abstract»

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  • Large negative dispersion in square solid-core photonic bandgap fibers

    Page(s): 666 - 670
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB) |  | HTML iconHTML  

    In this paper, a Ge-doping square solid-core photonic bandgap (PBG) fiber is proposed and the effective index of defect mode is investigated. Simulations show that, at the starting wavelength of the defect mode, neffd (the effective index of defect mode) changes rapidly due to the PBG effect, which induces large negative dispersion in fiber. This mechanism is different from the mode coupling case in dual-core concentric fibers, and the dispersion characteristic is more robust to structural deviations. View full abstract»

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  • Solid-state lasers at the stability limit: constant beam properties over large power ranges

    Page(s): 671 - 676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB) |  | HTML iconHTML  

    Without adaptive optics high-power lasers suffer either from poor beam quality or limited power ranges. A laser can be forced to operate on its stability limit by self-adaptive overcompensation resulting in constant and good beam quality over a large power range. With this technique, the brightness of a Nd:YAG laser was increased by almost an order of magnitude despite highly aberrated thermal lens in the laser rod. View full abstract»

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  • Dependence of the neodymium random laser threshold on the diameter of the pumped spot

    Page(s): 677 - 685
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB) |  | HTML iconHTML  

    We experimentally studied the dependence of the threshold energy density Eth/S in Nd0.5La0.5Al3(BO3)4 random laser on the diameter of the pumped spot d and found that at d≥130μm, Eth/S is proportional to 1/d+const. This functional dependence is different from the one commonly expected in the case of diffusion, ∝1/d2+const. However, the obtained experimental dependence does not mean the failure of the diffusion model. Calculating the mean photon's residence time τresp (which photons, making their diffusion-like random walks, spend inside the gain volume) as the function of d and further assuming that Eth/S∝(τpres)-1, we predicted the experimentally obtained functional dependence, ∝1/d+const. The major difference between our model and that of and was in the boundary conditions. View full abstract»

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  • Imposing a Gaussian distribution in multichannel laser resonators

    Page(s): 686 - 693
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    Intracavity coherent addition of several laser channel distributions where one is a Gaussian distribution and the others are multimode distributions is investigated. It is shown experimentally that the Gaussian distribution is inherently imposed on all the channels. A model for analyzing coherent addition of two or four beams is developed and used to support the experimental results. View full abstract»

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  • Characterization of new FIR laser lines from CHD2OH

    Page(s): 694 - 696
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    In this work, we report new optically pumped far-infrared (FIR) laser lines from CHD2OH. A waveguide CO2 laser of wide tunability (290 MHz) was used as pump source, and a Fabry-Pe´rot open cavity was used as a FIR laser resonator. Optoacoustic absorption spectra were used as a guide to search for new FIR laser lines. We could observe 15 new laser lines in the range from 116.4 to 401.4 μm. The lines were characterized according to wavelength, relative polarization, relative intensity, and optimum working pressure. The transferred Lamb-dip technique was used to measure the frequency absorption transition both for the new and previously reported laser lines. View full abstract»

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  • Two-dimensional a-Si:H n-i-p photodiode array for low-level light detection

    Page(s): 697 - 703
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    This paper presents the design, fabrication process, and performance evaluation of a two-dimensional hydrogenated amorphous silicon (a-Si:H) n-i-p photodiode array, developed specifically for low-level light sensor applications. The design of the device is simpler than conventional active-matrix-arrays based on thin-film transistor (TFT) addressing electronics, owing to the utilization of the a-Si:H switching diodes for signal readout. The discussed technological developments are aimed to minimize the leakage current and to enhance the external quantum efficiency. The current-voltage characteristics of the sensing and switching diodes are analyzed to identify the sources of the excess leakage current. The optical losses in the photodiodes with an ITO/a-SiNx:H antireflection coating have been minimized using numerical modeling. Description of the peripheral electronics and associated timing diagrams along with the results of the detector characterization, including the linearity and response time measurements, are presented and discussed. View full abstract»

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  • Improved gain performance of high concentration Er3+-Yb3+-codoped phosphate fiber amplifier

    Page(s): 704 - 708
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    The rate equations and power evolution equations of erbium/ytterbium codoped phosphate fiber amplifiers are solved numerically and its results are compared with measured data in literature. Based on the numerical analysis, optimal erbium and ytterbium codoping concentrations are supposed, and with a pump power of 224 mW and a fiber length of 3.6 cm, the internal gain of 31.0 dB and gain per unit length of 8.6 dB/cm may be achieved in the fiber with the optimal codoping concentrations. View full abstract»

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  • Performance sensitivity to system parameters in multiwavelength super-continuum sources

    Page(s): 709 - 716
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    We determine the fundamental cause of performance variation as a function of system parameters, in supercontinuum (SC) sources in a normal-dispersive fiber, with high-order nonlinearity effects included. The variations in the sliced-pulse quality with respect to the soliton order N, the input peak power, the slicing filter bandwidth, as well as the optimization of the fiber length and the slicing wavelength, are numerically investigated. The results show that, at a constant average input power, narrower input pulses (or smaller N) can help achieve broader output spectrum but at the expense of degradation in the sliced-pulse quality. Better quality of the sliced pulses can be obtained by using a slicing filter with wider filter bandwidth. Besides, the input peak power is found to have significant impact on the choice of the suitable slicing wavelength. These results can facilitate the optimization of system parameters in designing SC sources for optical transmission applications. View full abstract»

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  • Optimization of photomixers and antennas for continuous-wave terahertz emission

    Page(s): 717 - 728
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1136 KB) |  | HTML iconHTML  

    We have studied terahertz emission from interdigitated finger photomixers coupled to planar antenna structures. Using both pulsed and continuous-wave excitation, polarization measurements reveal that the antenna design dominates the properties of the radiated output at frequencies below 0.6 THz, while the efficiency at higher frequencies is additionally dependent on the design of the photomixer fingers. We have produced terahertz maps of the device, characterizing the photomixer by measuring the generated power as a function of the excitation position. Together, these measurements have allowed us to understand better the distinct roles of the photomixer and antenna in emission at different frequencies and, hence, independently optimize these components. View full abstract»

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  • Characteristics of all-optical ultrafast gate switches using cascade of second-harmonic generation and difference frequency mixing in quasi-phase-matched lithium niobate waveguides

    Page(s): 729 - 734
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    In all-optical gate switches that employ the cascade of second-harmonic generation and difference frequency mixing in quasi-phase-matched (QPM) lithium niobate (LN) devices, walkoff between the fundamental and second-harmonic pulses causes crosstalk of the switch. We numerically calculate the switching performance of QPM-LN waveguide devices with consideration for the crosstalk effect, and discuss the favorable choice of the nonlinear optical tensor element for the LN crystal. In the analyses, the device length is maximized for a given bit rate under the condition that the crosstalk is maintained below a critical level that is determined by the allowable power penalty for the switched signal. It is shown that the time offset between the gate and signal pulses can compensate for the walkoff, and can significantly improve the switching efficiency. In ultrafast operation beyond 1 Tbps, the use of the nonlinear optical tensor element d31 is found to be favorable when compared to the use of the commonly used maximum tensor element d33. View full abstract»

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  • Time dependence of soliton formation in planar cells of nematic liquid crystals

    Page(s): 735 - 740
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB) |  | HTML iconHTML  

    Spatial optical solitons can be observed in bulk nematic-liquid-crystal cells with an entrance window and a bias voltage applied over the cell to enhance the optical nonlinear effect of laser-induced molecular reorientation. The soliton-induced waveguide is observed in transmission by use of a second light source and crossed polarizers. This setup allows us to investigate the time dependence of the molecular reorientation that sustains the soliton-like beam propagation. Results from a numerical simulation are in good agreement with the experimental results, which confirms the validity of our model. View full abstract»

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  • A novel ultracompact two-mode-interference wavelength division multiplexer for 1.5-μm operation

    Page(s): 741 - 746
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    A novel ultracompact 2×2 wavelength division multiplexer (WDM) for 1.55-μm operation based on highly dispersive two-mode interference (TMI) was designed, theoretically modeled, and verified using a finite-difference-time-domain (FDTD) method. A two-moded waveguide assisted with a dispersive tooth-shaped grating provided a mode-dependent reflection band of central wavelength at 1.55 μm. The wavelengths of 1538 and 1572 nm that were at the band edges and had the lowest reflection losses and relatively high dispersion were selected for wavelength multiplexing. The result showed that the wavelengths were separated by grating dispersion in a coupler length of 75 μm which was much shorter than the required length of 1.1 mm in a regular TMI multiplexer of no grating. Insertion loss of about 1.7 dB and channel contrast of about 12 dB were achieved. View full abstract»

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  • 5th International Conference on Numerical Simulation of Optoelectronics Devices (NUSOD'05)

    Page(s): 747
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  • IEEE/OSA Journal of Display Technology

    Page(s): 748
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    Freely Available from IEEE
  • IEEE Journal of Quantum Electronics information for authors

    Page(s): c3
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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