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Quantum Electronics, IEEE Journal of

Issue 3 • Date Mar 1994

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Displaying Results 1 - 25 of 29
  • Modulation of a two-mode laser

    Page(s): 854 - 859
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    We analyze a two-mode laser, described by rate equations, whose gain is periodically modulated. The nature of the response varies significantly with the modulation amplitude. We study both the small modulation in which the pump parameter remains always above the lasing threshold for the second mode, and the deep modulation in which the pump parameter is located during part of the cycle between the single-mode and the two-mode thresholds. Apart from the strong McCumber nonlinear resonance at the relaxation oscillation frequency, we describe a rich variety of nonlinear properties such as multistability among periodic and quasi-periodic solutions, and small resonances in the vicinity of the second (and lower) internal frequency. We also identify domains that suggest the occurrence of the traditional routes to chaos View full abstract»

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  • FEL operation in a magnetostatic field produced by current-carrying linear wire

    Page(s): 776 - 780
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    It is shown that free-electron laser (FEL) operation is possible in a magnetostatic field produced by a dc-current-carrying long linear wire. A single-particle approach is used to derive the small-signal gain equation in this configuration. The maximum value of the small-signal gain is proportional to the cube of the interaction region length in our case, as in the ordinary circularly polarized FEL View full abstract»

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  • Analysis of the impedance of a coaxial, large-bore copper-vapor laser

    Page(s): 763 - 769
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    The impedance of the laser head of a 100-W copper-vapor laser is investigated. The laser head is of a coaxial geometry, which is commonly used for longitudinally electrically excited, pulsed-gas lasers. The plasma conductivity is estimated using the available data on plasma parameters. The effect of radial gradient of the gas temperature and electron density is considered. The tube inductance and capacitance are estimated and the combined effect is demonstrated. The skin effect is considered. A method to calculate the exact influence of the skin effect on the tube impedance is presented. The full calculation procedure is demonstrated for the case of a 100-W, 8-cm-diameter, copper-vapor laser. The consequent impedance is used to calculate the laser current under given excitation conditions. Very good agreement exists between the calculated and measured laser current. The metal-sleeve diameter is found that is optimal for power matching View full abstract»

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  • Picosecond time-lenses

    Page(s): 827 - 837
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    There is an interesting analogy between the spatial problem of Fresnel diffraction and the temporal problem of first-order dispersion. This space-time analogy was recently extended to propose a time-domain analog to spatial imaging that allows for the distortionless expansion of compression of optical waveforms in time. This process is called temporal imaging. The extension includes the idea of a time-lens as a dual of a spatial lens (regular lens). The time-lens is simply a quadratic optical phase modulator in time, which is approximated by a portion of a sinusoidal phase modulator. Thus, by using phase modulators as lenses and grating pairs as dispersive elements, complete temporal imaging systems can be constructed in exact duality with spatial imaging systems. However, for practically useful time-lenses, considerable modulation is required at fairly high frequencies. The main body of the paper is the detailed design and development of a practical time-lens. This is addressed in Section II, where a resonant microwave modulator is developed based on a LiNbO3 loaded waveguide. Multiple passes are obtained through the modulator using an off-axis path in a stable optical resonator. At 5.2-GHz operation, 44 radians of phase modulation is obtained at 1.06-μm wavelength for 13 W of microwave power. This corresponds to a time-lens with 31-ps aperture and 1.9-ps resolution. This was confirmed by demonstrating temporal focusing of 45-ps pulses to 1.9 ps. By optimizing the design of the time-lens and better thermal engineering, it may be possible to obtain subpicosecond resolution View full abstract»

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  • Behavior of the positron beam of the super-ACO storage ring in response to a modification of the RF frequency for free-electron laser experiments

    Page(s): 781 - 792
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    The macrotemporal structure of the super-ACO storage ring free-electron laser (FEL) can be either continuous, pulsed, or chaotic, and can present some rapid fluctuations. The temporal evolution of a storage ring FEL involves both the longitudinal motion of the positron beam (especially the synchrotron oscillations) and the FEL dynamics, as in a coupled system. Studies on the dynamics of the positron beam are performed here, in the goal to have a stable source for FEL applications, and to determine the conditions for a stable Q-switching experiment, The employed method is to study the influence of a controlled change of the radio frequency (RF) (modulation or frequency jump) on the beam. A simple theoretical model taking into account the perturbed RF system is presented to help the understanding of the experimental data. The different methods of measurement are described. Then, the results are given for several experimental conditions and the influence of different possible adjustments (synchrotron feedback, RF loop...) is presented. Consequences are derived for the FEL View full abstract»

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  • Integrated lossless InGaAsP/InP 1-to-4 optical switch

    Page(s): 717 - 723
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    The fabrication and performance of a 1-to-4 channel optical splitter/combiner are described. The design is based on the integration of a number of twin-guide amplifiers interconnected by active ridge waveguides. Lossless operation is seen fiber-to-fiber for all four ports for TE input light, with a 3-dB bandwidth of 20 nm View full abstract»

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  • Polarization dependence of linewidth enhancement factor in InGaAs/InGaAsP MQW material

    Page(s): 635 - 639
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    Measurements and calculations on the differential gain, the differential refractive index, and the linewidth enhancement factor have been performed for unstrained quantum-well (QW) material. The differential refractive index is considerably lower for the transverse magnetic (TM) polarization than for the transverse electric (TE) polarization, which is ascribed to absence of the plasma effect for the TM polarization. This has implications for the linewidth enhancement factor and thus linewidth and chirp in QW lasers View full abstract»

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  • The starting mechanism in coupled-cavity modelocked laser systems

    Page(s): 812 - 817
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    We present what we believe to be the starting mechanism in coupled-cavity additive pulse modelocked (APM) laser systems. The etalon effect of the coupled cavity forces the main cavity to lase at two separate frequencies, thus producing short and strong mode beating “noise bursts” that can overcome dynamic gain saturation in large emission cross-section gain media. As a result, self-starting is possible for the NaCl:OH coupled-cavity color center laser. The dependence of the etalon effect on the cavity length detuning and its role in the dynamics of the APM process and in self-stabilized picosecond coupled-cavity lasers are discussed. The experimental observation of THz-mode beating fluctuations produced by the mode structure of a coupled-cavity NaCl:OH color center laser supports our model View full abstract»

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  • The two-photon absorption semiconductor waveguide autocorrelator

    Page(s): 838 - 845
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    In this paper, we report a novel semiconductor waveguide autocorrelator that employs two-photon absorption (TPA), rather than the more commonly used second-harmonic generation, as its nonlinear mechanism. An introduction to TPA is given, and the reasons for its use in the autocorrelator are explained with reference to nonlinear absorption experiments. We then describe the fabrication of the p-i-n GaAs/AlGaAs waveguide. The initial experiments carried out with a single beam in the waveguide are described and fitted to theory. Autocorrelation traces for both a CW modelocked Nd3+:YAG laser at 1.06 μm and a Q-switched InGaAsP/InP laser at 1.3 μm are presented and their pulsewidths obtained by means of a theoretical model. The sensitivity and resolution of the TPA waveguide autocorrelator are then discussed, as is a proposal for a multiple-contact TPA waveguide autocorrelator, designed so that the two pulse trains are counter-propagating. This would result in an autocorrelator from which the laser pulsewidth could be obtained in a single measurement, with no moving parts, and which could be integrated with a semiconductor laser View full abstract»

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  • The effect of emittance inhomogeneous broadening on the brightness of a magnetic undulator

    Page(s): 793 - 799
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    In this paper we discuss the degradation of the undulator brightness induced by the spatial and angular distributions of the e-beam. The obtained results are general in the sense that they hold regardless of any matching condition. The relevance of the analysis to free-electron laser dynamics is also commented upon View full abstract»

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  • Design and modeling of asymmetric Fabry-Perot electrooptic modulators containing a polymeric film

    Page(s): 724 - 731
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    Asymmetric Fabry-Perot modulators containing an electrooptic polymeric film are described. The designs of these structures are optimized for reflection operation by maximizing both cavity finesse and the effective field strength acting across the spacer region, hence minimizing drive voltages. The electrooptic responses of these devices are modeled and the voltages required to realise 3-dB and 10-dB modulation are calculated. It is thus demonstrated that organic thin-film-based Fabry-Perot devices are potential candidates for high-speed, low-drive-voltage, electrooptic switches, modulators, and interconnect elements. Experimental results from prototype devices are also presented View full abstract»

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  • Analysis and simple tuning scheme of asymmetric Y-lasers

    Page(s): 654 - 659
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    We present an analysis of interferometric lasers in Mach-Zehnder configuration with emphasis on the recently realized asymmetric Y-laser, leading to simple design and tuning rules. By tailoring the Mach-Zehnder (MZ) filter function we obtain a large variety of designable channel spacings together with improved sidemode suppression and easy access for wavelength division multiplexing (WDM) functions and wavelength conversion View full abstract»

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  • Self-trapped propagation in the nonlinear cubic-quintic Schrodinger equation: a variational approach

    Page(s): 818 - 821
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    In the framework of a variational approach, we determine approximate analytical expressions for the self-trapped solutions in the cubic-quintic nonlinear Schrodinger equation (NLCQSE) and compare our solutions with the available exact ones. Through our approach, we also discuss the stability of the solutions and give simple explanations to the physical meaning of the bistable soliton regime, which can be obtained for some parameter values View full abstract»

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  • Polarization dependence of optoelectronic properties in quantum dots and quantum wires-consequences of valence-band mixing

    Page(s): 640 - 653
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    The electronic bandstructure in quantum dots and quantum wires is studied, including the valence-band mixing effects. Based on the bandstructure, results for the polarization dependence of absorption and gain (at room temperature) are examined. The related differential gain and the α-parameter is also studied. Our results show that it is extremely important to include valence-band mixing effects in predicting the laser performance of such structures View full abstract»

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  • Polarization-insensitive optical amplifier with tensile-strained-barrier MQW structure

    Page(s): 695 - 702
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    A new approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of a tensile-strained-barrier MQW structure that enhances TM mode gain. Polarization sensitivity below 0.5 dB is realized at a wavelength of 1.56 μm. A signal gain of 27.5 dB is obtained along with a saturation output power of 14 dBm. Deriving the refractive indices of well and barrier layers from both experiment and theory, we succeed in separation of the effect of the confinement factor and the gain coefficient. It is determined that TM mode gain enhancement in this structure is primarily due to the increase in the confinement factor View full abstract»

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  • Laser tuners and wavelength-sensitive detectors based on absorbers in standing waves

    Page(s): 732 - 749
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    We propose a new method for making laser tuners, and wavelength-sensitive or tunable detectors, that is based on absorbers in standing waves. Because the method does not rely on mechanical movement or changes in refractive index, it may offer high-speed tunable devices whose range is not constrained by limits on the size of refractive index changes. The devices can be made either in a longitudinal form by back reflection, or in a transverse form by interfering beams at an angle on a surface. We give theoretical models for these structures, and illustrate the concepts with various specific device designs. These include a narrow band detector based on transverse gratings, a simple wavelength sensitive longitudinal structure with a single absorber, and a two-absorber longitudinal structure capable of many functions, including a narrow band detector, a two wavelength detector, a wavelength measuring detector, a continuously variable laser tuner, and a laser phase controller. These devices can all be made using layered semiconductor growth and lithography, and are particularly suited to quantum wells. The devices are applicable to wavelength division multiplexing and switching, and to sensors and spectroscopy View full abstract»

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  • Influence of thermal effects on the tunability of three-electrode DFB lasers

    Page(s): 660 - 667
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    An analysis of the influence of thermal effects on the tuning behavior of a three-electrode distributed-feedback (DFB) laser is presented. In the adopted three-dimensional model, nonuniform injected current distribution is taken into account. The electronic and thermal tuning mechanisms are compared, and results for a typical three-electrode PS-DFB laser are presented and discussed View full abstract»

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  • Theory of soliton pulse forming in an actively modelocked fiber laser

    Page(s): 822 - 826
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    Generation of subpicosecond solitons in active modelocked fiber lasers is investigated, both analytically and numerically. The laser model takes into account the pulse dispersive spreading, self-phase modulation, finite amplification bandwidth, pump depletion and Raman self-frequency shift. Our analytical theory, which is based on the inverse scattering method perturbation approach, allows us to calculate the steady-state parameters of the soliton pulse. The analytic predictions are confirmed by numerical simulation. It is shown that the minimal pulse duration may be achieved provided that the Raman self-frequency shift is suppressed by the phase modulator View full abstract»

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  • Spontaneous filamentation in broad-area diode laser amplifiers

    Page(s): 685 - 694
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    The stability of a plane wave propagating in single- and double-pass broad-area diode laser amplifiers is analyzed. It is found that laterally periodic perturbations exhibit a longitudinal variation that is a mixture of exponential growth and periodic oscillation. The latter oscillation has a spatial period related to the Talbot distance. Due to the interaction between these two effects, double-pass amplifiers become unstable against lateral perturbations, and the field spontaneously collapses into a periodic array of filaments. Experimental results are presented that show good agreement with the theoretical analysis View full abstract»

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  • Fluctuational crosstalk in Ti:LiNbO3 directional coupler switches

    Page(s): 713 - 716
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    It has been found that the fluctuations in the Ti concentration along waveguides of Ti:LiNbO3 directional coupler switches degrade the switch extinction ratio and introduce an unwanted crosstalk between both channels. We discuss analytically the effect of effective optical index fluctuations on the transfer matrix of the optical switch. We demonstrate the sensitivity of the mismatch to the statistics of the fluctuations of the Ti concentration View full abstract»

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  • Numerical model of stimulated Brillouin scattering excited by a multiline pump

    Page(s): 805 - 811
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    A theoretical formulation and numerical simulation of the process of stimulated Brillouin scattering (SBS) excited by a multiline incident beam is presented. The one-dimensional code includes pump depletion and contributions from resonant and off-resonant acoustic gratings. For line separations up to the order of the spontaneous Brillouin linewidth, gain enhancement is accompanied by phase shifts between lines due to complex, off-resonant terms, which may result in a degradation of conjugation fidelity. For larger frequency separations, the degree of amplification is dependent on the ratio of the coherence length of the pump line spectrum to the SBS gain length. Comparisons with experimental data on reflectivity versus line separation show very good agreement View full abstract»

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  • Q-switching and frequency doubling of solid-state lasers by a single intracavity KTP crystal

    Page(s): 800 - 804
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    The electrooptic characteristics of the KTP crystal are analyzed in detail and Q-switched operation of a diode-laser-pumped microchip Nd:YVO4 laser is reported using an intracavity KTP crystal. The KTP was used also as a frequency-doubling crystal in type II phase matching for generating pulsed green beams. Low loss and high efficiency characteristics were realized by eliminating two components, i.e., a Q-switching or a frequency-doubling crystal and a polarizer, in comparison with the conventional frequency-doubling configuration. Up to 15.4 W peak output and 18-ns width green power was obtained with 760-mW pumping power on the Nd:YV4 microchip, which corresponded to 616 times enhancement of the CW output power View full abstract»

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  • Small-signal resonance distortion of semiconductor lasers

    Page(s): 680 - 684
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    Small-signal expressions for the second- and third-order resonance distortion of a semiconductor injection laser are reported. Results are valid even if the frequencies involved are not closely spaced, and are applicable to high-power lasers for which previously published results may not be valid. The new results are more accurate than prior results when the product of the gain compression factor and the photon density is relatively large, or when low frequencies are of interest. The second-order distortion-to-carrier ratio depends on the resultant frequency but not on the individual frequencies involved in nonlinear mixing. The third-order distortion-to-carrier ratio in general depends on individual mixing frequencies, but if all frequencies are small compared to the resonance frequency, then this result also depends primarily on the resultant frequency View full abstract»

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  • A superluminescent diode at 1.3 μm with very low spectral modulation

    Page(s): 703 - 712
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    An edge-emitting superluminescent diode has been fabricated from an MOCVD-grown InGaAsP/InP double heterostructure, for light emission at 1.3 μm. Using a ridge-waveguide geometry with an integrated absorber, the goals of high power coupled into a single-mode fiber and very low spectral modulation are fulfilled. Interferometric measurements of the residual modulation determine the location of internal optical reflections in the device. The results are interpreted and compared to the predictions of a transmission-line model View full abstract»

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  • Area scaling in N2 waveguide lasers

    Page(s): 759 - 762
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    The area scaling in a nitrogen (N2: 337.1 nm) laser excited by the similar longitudinal discharges in single- and multichannel laser structures has been experimentally studied. The results demonstrate the capability of the area scaling method for increasing the average power and pulse-repetition frequency (PRF) of the laser. The variation of the laser output with the channel area and the effects of similar discharges are analyzed 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