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Quantum Electronics, IEEE Journal of

Issue 4 • Date April 1988

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Displaying Results 1 - 14 of 14
  • The effects of wiggler taper rate and signal field gain rate in free-electron lasers

    Page(s): 598 - 608
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    A dimensionless formulation of the motion of electrons in free-electron lasers (FEL) with tapered wigglers is derived that takes into account the cumulative effects of tapering and signal field gain. The mathematical problem involves three small parameters: epsilon , measuring the slowness of spatial variations of the wiggler field; mu , the ratio of signal wavelength to wiggler period, and kappa , the square of the ratio of the plasma frequency to signal frequency. Two limits governing the relation between mu and epsilon and three limits governing the relation between kappa and epsilon are identified. The mathematical problems which result consist of the solution of strictly nonlinear oscillators with slowly varying parameters and small perturbation terms. Techniques from the asymptotic theory of nonlinear oscillations are used to derive results pertinent for FEL problems.<> View full abstract»

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  • Injection behavior and modeling of 100 mW broad area diode lasers

    Page(s): 609 - 617
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    The output from a single-frequency, narrow-linewidth GaAlAs diode laser was injected into a 100-mW broad-area diode laser. The injected laser emitted in a single longitudinal mode with up to 80 mW in a single, diffraction-limited, 0.5 degrees FWHM far-field lobe. The angle of the far-field lobe steered with injection frequency and broad-area laser bias current, displaying behavior similar to that observed with injected gain-guided laser arrays. A Fabry-Perot amplifier model which explains the injection behavior in terms of Gaussian beam propagation in a large optical cavity is proposed. The model provides criteria for optimizing locking bandwidth, beam steering, and injection efficiency.<> View full abstract»

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  • Transmission of linearly polarized infrared light through curved hollow dielectric waveguides

    Page(s): 618 - 624
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    A model for the propagation of light from a CO/sub 2/ laser along hollow circular-bore dielectric waveguides is proposed. The guides may have one or more sections with fixed finite radius of curvature, and the light is linearly polarized. Comparison to experimental results shows that the improvement over previous models is very marked.<> View full abstract»

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  • Modeling of the frequency modulation response of semiconductor diode lasers

    Page(s): 625 - 634
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (893 KB)  

    The modulation response of GaAlAs semiconductor diode lasers has been studied theoretically, with emphasis on wavelength modulation or frequency chirp. The laser model used is a nonlinear rate equation model that incorporates the wave equation for the lateral waveguide modes of the laser. Lateral diffusion of carriers in the active layer of the laser is taken into account via a one-dimensional diffusion equation. A small-signal analysis of the model has been performed to obtain the modulation response. The calculated amplitude and phase of the wavelength modulation relative to the power modulation are in good agreement with experiments. It is found that carrier diffusion has only a moderate influence on the modulation response.<> View full abstract»

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  • Effects of well number, cavity length, and facet reflectivity on the reduction of threshold current of GaAs/AlGaAs multiquantum well lasers

    Page(s): 635 - 640
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    The optimum design for reducing the threshold current of GaAs/AlGaAs multiquantum well lasers is determined experimentally. The lowest threshold current density is realized by using single and multiquantum wells at long and short cavity lengths, respectively. The threshold current has a minimum at the optimum cavity length: the minimum threshold current is smaller for a larger number of quantum wells, and the optimum cavity length is inversely proportional to the number of wells. Experiments are compared to the theory developed by P.W.A. McIlroy, et al. (ibid., vol.21, no.12, p.1958-63, 1985) and limiting performances of quantum well lasers with various numbers of wells are presented. The reduction of the threshold current by high reflectivity coatings is also demonstrated, and a threshold current as low as 1.86 mA at 15 degrees C is reported.<> View full abstract»

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  • Anisotropic four-wave mixing in cubic photorefractive crystals

    Page(s): 652 - 659
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    The anisotropic four-wave mixing in the scheme recently proposed by S.I. Stepanov and M.P. Petrov (Opt. Commun. vol.53, p.64-8, 1985) is studied. The main feature of this interaction arrangement is that the same phase hologram (index grating) has opposite contrasts for orthogonally polarized, counterpropagating waves. The coupled nonlinear equations, in the case of transmission and reflection gratings, for the pi /2 photorefractive phase shift are exactly solved, and their properties are discussed in detail. The numerical evidence of the effects of bistability and self-oscillation is included.<> View full abstract»

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  • Closed-form solution for parametric second Stokes generation in Raman amplifiers

    Page(s): 660 - 664
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (485 KB)  

    The efficiency of a first Stokes Raman amplifier can be seriously reduced by the generation of a second Stokes beam. The dominating process for this generation is often a Raman four-wave mixing interaction which couples the pump and second Stokes beams. A one-dimensional model for this effect has a closed-form solution, simply described in terms of an equivalent input, under conditions where high first Stokes conversion efficiency is possible. Excellent agreement with numerical integration results has been obtained. Use of the model for maximizing conversion efficiency of pump beams with large temporal or spatial intensity nonuniformity is described, with an example worked out for a triangular pulse shape.<> View full abstract»

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  • Multirod resonators for high-power solid-state lasers with improved beam quality

    Page(s): 665 - 674
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    Many laser applications require high beam quality at high output power and a broad variation of the output power. The ratio of power variation Delta P/sub out/ to beam parameter product theta /sub m/-w/sub m/ for a single rod inside a stable resonator is a constant which depends on the intrinsic crystal parameters and the slope efficiency only. A broad range of the output power causes a large beam parameter product, i.e. a low beam quality. By using several rods inside the same resonator and by a suitable choice of rod position and resonator parameters, the output power range can be increased without reducing the beam quality. In the same way, the beam quality can be improved without reducing the output power. The details of multirod systems are discussed and compared to experimental results.<> View full abstract»

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  • Resonant phenomena in laser excitation of surface waves on solids

    Page(s): 675 - 682
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    Excitation of surface waves by a moving laser beam has been studied both theoretically and experimentally. Using periodic surface structures as an example, it is demonstrated that the type of excited wave and the rate of its growth depend resonantly on the beam velocity. Experimental data show that resonant excitation of different periodic surface structures can change the spatial distribution of the absorbed laser energy.<> View full abstract»

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  • Laser-induced ionization of air in the presence of preionization

    Page(s): 683 - 686
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    Ionization of air at different pressures is studied for the following situations: (1) a spark gap acting as a preionizer alone, (2) a preionizer with a pulsed CO/sub 2/ laser, (3) a preionizer with a CW CO/sub 2/ laser, (4) a preionizer with a Q-switched Nd:YAG laser, and (5) and a Nd:YAG laser with a CO/sub 2/ laser. Results are quantified and analyzed with respect to some available data.<> View full abstract»

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  • Thermal lensing in biologic medium

    Page(s): 693 - 696
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    A nonlinear effect for tissue response is reported which results from macroscopic changes in the refractive index of tissue due to its localized heating during laser irradiation. The effect, termed thermal lensing, arises when a high-intensity beam of light interacts with an absorbing medium and highly localized heating occurs. Localized heating causes thermal expansion which leads to a decrease in tissue density, inducing macroscopic spatial gradients in the index of refraction. A description is given of a series of experiments designed and performed to establish the existence of thermal lensing in a biological medium and quantify the effect of exposure parameters and medium properties View full abstract»

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  • An X-ray free-electron laser loaded with a periodic dielectric

    Page(s): 591 - 597
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    When a periodic medium is inserted along the axis of a free-electron laser (FEL), the synchronism condition between the electron beam and the electromagnetic wave is changed. This alteration permits a wider parameter selection than the conventional FEL, and provides for the possibility of X-ray operation. The device is a hybridization of the FEL and the stimulated-transition-radiation laser. Photon absorption by the periodic medium and scattering of the electrons limit the interaction length, but calculated gains are still high enough for oscillation. The analysis shows that ultrarelativistic electron beams and low-density foil materials give the most physically realizable parameters. Higher order resonant transition modes (r>1) should be used to maximize gain View full abstract»

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  • Analysis of a laser phased array using a distributed Y-junction analog

    Page(s): 687 - 692
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    An analysis is presented of a semiconductor-laser linear phased array which uses a distributed, evanescent-coupled version of Y-junction branches to achieve mode discrimination. As in the Y-junction array, the in-phase fundamental mode has the inherently highest round-trip gain. The advantage of easier mask generation and fabrication for the distributed coupler is offset by its poorer discrimination against higher order modes View full abstract»

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  • Two-dimensional simulation of laser diodes in the steady state

    Page(s): 641 - 651
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    A fully self-consistent steady-state two dimensional model of laser diodes is presented. The model consists of the simultaneous solution of the Poisson and the electron and hole drift-diffusion equations, the wave equation, and the photon rate equation. Excellent agreement with experiment is obtained for both gain-guided and index-guided laser diodes. Specific results are given for channeled-substrate planar (CSP) lasers. It is shown that comparable electron current confinement is provided by both internal strips (p-GaAs barriers) and zinc-diffused planar stripes. The confinement in the first case is due to energy barriers and in the latter case is due to lateral electric fields. For the holes, current spreading is shown to be reduced substantially for the planar stripes because of the use of high-resistivity n-cap layers. It is demonstrated that the thickness of the p-GaAs layers can be smaller than the minority carrier diffusion length since only a very small fraction of the laser light passes through the barriers 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