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Quantum Electronics, IEEE Journal of

Issue 12 • Date Dec 1994

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Displaying Results 1 - 25 of 38
  • Scaling of the nonlinear optical cross sections of GaAs-AlGaAs multiple quantum-well hetero n-i-p-i's

    Page(s): 2790 - 2797
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    We study the dependence of the Stark shift optical nonlinearity of GaAs-AlGaAs multiple quantum-well hetero n-i-p-i's on the number of quantum wells per intrinsic region in otherwise identical hetero n-i-p-i's. We determine that σeh, the nonlinear absorption cross section, is proportional to the number of quantum wells per intrinsic region. A study of the fluence dependence of σeh shows that the saturation carrier density is inversely proportional to the number of wells per intrinsic region. We find that the turn-on time of the nonlinear absorption change in our samples is independent of the number of quantum wells per intrinsic region. All of these results are consistent with the absence of retrapping of photogenerated carriers View full abstract»

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  • Observation of two emission lines in the p-type-Ge cyclotron resonance laser

    Page(s): 2778 - 2780
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    The stimulated far infrared emission of a p-type-Ge cyclotron resonance laser is investigated in the frequency range between 60 cm-1 and 80 cm-1. If the applied electric field is adjusted to achieve maximum output intensities, a single magnetic field tunable emission line is observed. By detuning the electric field a second line occurs in the laser spectrum. The presence of this line is governed by the amount of mixing between the Landau levels of the light and heavy holes induced by the electric field. From a comparison of the observed emission frequencies with calculated transition energies, a second laser transition is identified which appears in addition to the dominant n=1 to n=0 Landau level transition of the b-set View full abstract»

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  • Q-switched operation of quasi-three-level lasers

    Page(s): 2896 - 2901
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    A theoretical model for longitudinally pumped quasi-three-level lasers under Q-switched, repetitively Q-switched, and cw operating conditions is developed. The model is applied using 8% Ho:YAG as the gain medium, and it is found that for typical conditions the effective energy storage time can be much less than the upper state lifetime, in agreement with experiment but not predicted by earlier theories. This effect is attributed to details of laser design and pumping conditions, as opposed to being an intrinsic property of the gain material View full abstract»

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  • Analysis of frequency chirp in DFB lasers integrated with external modulators

    Page(s): 2756 - 2766
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    A mathematical formulation for DFB semiconductor laser integrated with external modulators is developed and presented. A set of rate equations governing the interaction between the field and the carrier in the DFB laser under the influence of the optical feedback from the modulator is established. Analytical expressions for the modulation-induced frequency chirp in the DFB lasers are derived. Characteristics and parameter dependences of the frequency chirp are examined View full abstract»

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  • Free carrier effect on the refractive index change in quantum-well structures

    Page(s): 2798 - 2802
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    Dielectric response of spatially inhomogeneous free carriers in quantum wells is studied by random phase approximation (RPA) for a high frequency (near infrared) light field. A general form for susceptibilities is derived for a guided optical mode. The analysis shows that a conventional treatment (Drude model) for the TE mode provides a good approximation. The susceptibility for the TM mode is almost the same as that for the TE mode, in spite of quantization of carrier motion, as long as the photon energy is much larger than the intersubband transition energy. The free carrier component of the refractive index change in quantum-well waveguides is thus isotropic near the band gap. Carrier confinement will not reduce the free carrier component in the linewidth enhancement factor around the lasing wavelength View full abstract»

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  • Optical absorption and refraction spectra in highly excited GaSb

    Page(s): 2771 - 2777
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    A theoretical estimate of carrier-induced changes in absorption and refraction spectra in GaSb is presented. The partly phenomenological electron-hole plasma model including band filling, band-gap renormalization, screening of the Coulomb interaction and the free-carrier plasma effect is used. A dominant contribution of the band filling and screening of the continuum-state Coulomb enhancement is observed. For the first time the influence of high lying conduction band valleys is taken into account. In addition, the model is applied to calculate the absorption and refraction spectra in doped material. The obtained results may prove to be useful in the design of GaSb optoelectronic devices View full abstract»

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  • Measurement of the barrier height of a multiple quantum barrier (MQB)

    Page(s): 2781 - 2789
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    A method of using a light-emitting diode structure with two active regions to measure the excess barrier height induced by the inclusion of a multiple quantum barrier structure is outlined. For a multiple quantum barrier structure previously used in a visible laser device, the resultant increase in barrier height was found to be 26 meV. The effect of the first barrier thickness on the produced barrier height is also investigated. It was found that by optimizing this parameter, the induced barrier height could be increased to 55 meV. These results are compared with those predicted by theory, and certain discrepancies between them are discussed View full abstract»

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  • Effect of illumination uniformity on GaAs photoconductive switches

    Page(s): 2866 - 2874
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    The dynamic behavior of a GaAs photoconductive switch was studied with an electro-optic imaging system during the first 2 ns after optical illumination. The switch behavior changed as a function of the spatial distribution of the optical illumination. Symmetric and asymmetric illumination schemes were investigated experimentally with our electro-optic imaging system. The electric fields were significantly enhanced in the regions of low photo-carrier density. Approximately 1 ns after illumination the simple longitudinal variation of the electric field gave way to nonuniform transverse structure. The experimental results were modeled by treating the switch as an integral part of a transmission line consisting of discrete elements. The experimental results matched the predictions of the transmission-line model in terms of the electric-field enhancements and efficiency View full abstract»

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  • Suppression of the intensity noise in a diode-pumped neodymium:YAG nonplanar ring laser

    Page(s): 2907 - 2913
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    We investigate the intensity noise properties of a continuous-wave diode pumped Nd:YAG ring-laser system and present results for an active feedback loop that suppresses the relaxation oscillation noise. This system reduces the intensity noise to within 6.1 dB of the quantum noise equivalent level (which is at 1.5×10-8/√Hz for 1.5 mA) for frequencies between 10 kHz to 300 kHz and to less than 1×10-7/√Hz for frequencies between 300 Hz and 10 kHz. The technical properties of the optimized feedback system are presented. The theoretical limits of performance for the system are discussed and it is shown that the performance is within 3.1 dB of these limits. We also present data from an optical beat experiment demonstrating that the intensity control system does not introduce any new features into the frequency noise spectrum View full abstract»

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  • Design and application of very low-loss abrupt bends in optical waveguides

    Page(s): 2827 - 2835
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    A new low-loss abrupt bend structure of the microprism type is proposed. This new bend uses a microprism to compensate for the phase difference of the phase front before and after the bend corner, so the entire phase front of the eigenmode is tilted properly, resulting in a very low-loss characteristic. Simulated results show that a normalized transmitted power of greater than 95% is achieved for a bend angle of 10°. Moreover, a phase compensation rule and its corrections are presented to determine the optimal prism parameters. Application examples of the microprism to design a very low-loss large-angle Z-bend and two cascaded Z-bends are also shown View full abstract»

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  • Optically pumped 13CD3OH: far infrared laser lines and assignment

    Page(s): 2946 - 2949
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    Fourier transform and IR optoacoustic absorption data of 13 CD3OH were used to search for new FIR laser lines. We have used a waveguide CO2 laser of 300 MHz tunability as the optical pumping source. We report the observation and characterization of 13 new lines. Three of these lines are associated with absorbing transitions appertaining to the weak 13CD3 asymmetric bending mode View full abstract»

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  • Exact analytic solutions to the nonlinear wave equation for a saturable Kerr-like medium: modes of nonlinear optical waveguides and couplers

    Page(s): 3006 - 3016
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    Exact analytic solutions to the nonlinear wave equation for a lossless saturable Kerr-like medium are found. The nonlinearity is an intensity-dependent refractive index which saturates according to the model n2=n02±a|E|2/(1+b|E| 2). The solutions to the wave equation are used to determine the TE power-dependent dispersion relations, and therefore the guided modes, of a single waveguide structure and of a directional coupler whose coupling medium is the nonlinear saturable material. Although the interaction between the sinh- and cosh-like modes of the coupler, and therefore the coupling length, is not treated in this work, it is shown that the critical power, defined in the literature to be the level of input power above which 100% of the power cannot be switched between the guides of a coupler, is a mathematical misinterpretation in both saturable media as well as in nonsaturable Kerr media. The absence of a critical power in single waveguide structures is also demonstrated. Parameters of GaAs-based waveguides and of a GaAs-GaAlAs MQW coupling medium are used in the numerical analysis View full abstract»

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  • Coupling properties in periodic waveguides and in multiple quantum-well waveguides

    Page(s): 2811 - 2816
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    General formulas describing field distributions and eigenvalue equations are presented for both TE and TM modes of a periodic waveguide or a multiple quantum-well waveguides with a periodic square wave refractive index profile. The effects of the structural parameters on the mode coupling properties are analyzed and the single-mode propagation is discussed for some GaAs/AlGaAs optical waveguides View full abstract»

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  • Oscillation mode selection using bifurcation of chaotic mode transitions in a nonlinear ring resonator

    Page(s): 2986 - 2997
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    This paper demonstrates the effectiveness of an adaptive parametric control method for searching and switching among a large number of multistable oscillation modes using chaotic mode transitions. The adaptive control is used to select nonlinear oscillation modes in an electro-optic ring resonator. In the adaptive control scheme, the result of a simple test of resonator output is fed back to a single parameter, pump laser power, governing bifurcation to and from chaos. The test is the presence or absence of a target code in the oscillation waveform of the resonator output. Chaotic mode transition phenomena, called chaotic itinerancy, are investigated in terms of code dynamics, and the results are used to determine the optimal parameters for the adaptive control View full abstract»

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  • Efficient design of multistage magnetic pulse compression

    Page(s): 2934 - 2938
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    We have developed a two stage magnetic pulse compression (MPC) system by optimizing the distribution of the compression ratio at each stage. The maximum energy transfer efficiency of the MPC was 88%. With this MPC and SI thyristors we obtained the CVL output power of 103 W at a repetition rate of 5 kHz View full abstract»

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  • High-speed InP-InGaAs heterojunction phototransistors employing a nonalloyed electrode metal as a reflector

    Page(s): 2889 - 2895
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    High-speed InP-InGaAs heterojunction phototransistors (HPT's) with a base terminal (three-terminal HPT's) have been fabricated. These HPT's have nonalloyed electrodes functioning as reflectors and a configuration in which light is incident through the substrate. These features lead to an increase in quantum efficiency in spite of the thin base and collector light-absorbing layers. Optical gain dependence on collector current is weak because of the low recombination current at the emitter-base interface. Maximum optical-gain cutoff frequencies of 22 and 14 GHz are obtained for a 3×3-μm2 emitter HPT illuminated by 1.3- and 1.55-μm light, respectively. This HPT has the capability of operating as a high-speed heterojunction bipolar transistor (HBT) as well. A current-gain cutoff frequency (fT) of 128 GHz is obtained for a 3×9-μm2 emitter HBT fabricated on the same wafer. Equivalent circuit analysis, in which all the components are determined by measuring both the electrical and optical characteristics of a three-terminal HPT, shows good agreement with experimental results View full abstract»

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  • Modal properties of depressed cladding semiconductor waveguides and lasers

    Page(s): 2817 - 2826
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    The TE modal properties of three symmetric core (uniform, parabolic, and linear) depressed cladding slab waveguide structures are investigated for situations appropriate for use as lasers and routing waveguides. The results show that if the confinement factor, or mode size, is the criterion for comparison, there is little difference between the standard and depressed cladding cases for guides which are near the cutoff of the higher order modes. The primary difference is in the fraction of the mode which overlaps the cladding regions, which is always smaller for the depressed cladding cases. We show that there are numerous combinations of conditions leading to spot sizes comparable to the vacuum wavelength of light. Experimental data are presented for three parabolic core depressed cladding AlxGa1-xAs heterostructures doped to form lasers. In particular, the measured Gaussian equivalent spot size deduced from far-field measurements agree well with model situations for the largest core sizes. The largest Gaussian equivalent near-field spot size was ~1.2 μm, and resulted in a divergence angle of ~30° (full width half power) and a threshold current density only 50% larger than a standard small optical cavity laser structure optimized for maximum confinement factor. The scaling laws of amplifiers and lasers with confinement factor are discussed. Experimental routing tests were performed using rib delineated raised cosine S bends. The symmetric depressed cladding laser structure was found to have a much lower bend loss than the standard structure, leading to tighter routing geometries with an etch depth which did not penetrate the quantum well View full abstract»

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  • Sub-Poissonian and super-Poissonian photon statistics in a twin-core doped optical fiber

    Page(s): 2836 - 2841
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    In this paper, we develop a quantum statistical theory of light propagation in a twin-core doped optical fiber. The optical nonlinearity induced by the atomic dopants in the fiber dramatically modifies the quantum fluctuations in the paraxial photon modes. We find that with appropriate arrangement of the device, the input light field with the usual Poissonian photon statistics can be transformed into sub- or super-Poissonian photon statistics. For the sub-Poissonian photon statistics, the quantum noise in the photon numbers in the paraxial modes is reduced below the level of the noise in the usual laser field View full abstract»

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  • Analysis of pump probe measurements and carrier overflow effects in multiple quantum-well optical amplifiers

    Page(s): 2767 - 2770
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    We present a theoretical study of structure dependent effects on carrier dynamics in simulated pump probe experiments of quantum-well optical amplifiers. We find that the dynamics of the unconfined carriers alter the probe transmission. We show that local capture has an effect which is similar to that of carrier cooling, and that by taking into account the carrier induced waveguide loss in a dynamic fashion, we can explain a previously measured transmission overshoot View full abstract»

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  • Er3+:YAlO3 upconversion laser

    Page(s): 2914 - 2924
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    Upconversion lasing in Er:YAlO3 is reported. Laser emission was produced using both sequential two-step pumping and cross-relaxation energy transfer. In addition, photon avalanche upconversion pumping was demonstrated. Selection among these pumping mechanisms is determined by the pump wavelength, and laser operation was obtained with excitation between 785 nm and 840 nm. The highest laser output power was achieved at 34°K, where 918 mW of pump power at 807 nm produced 121 mW of TEM00 emission. The optical conversion efficiency was 13%. Repetitively Q-switched operation is reported, and the temporal- and temperature-dependence of the laser output is discussed View full abstract»

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  • A coupled mode theory for electron wave directional couplers

    Page(s): 2803 - 2810
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    In this paper, a coupled mode theory for electron wave directional couplers is presented. This theory includes the dephasing effects on electrons due to temporally random collisions with lattice ions and other electrons in the system. This is done by considering the phase coherence length Lc as a single lumped parameter of the material. Using this model, the effects of temperature and other random dephasing collisions in electron wave devices can be studied easily. As an example, this model is applied to study the switching behavior of the electron wave directional coupler switch View full abstract»

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  • Single-mode operation of diode-pumped Nd:YAG lasers by pump-beam focusing

    Page(s): 2902 - 2906
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    We present a theoretical study of the maximum single frequency power that can be obtained from a simple coaxially end-pumped Nd:YAG laser. The approach is general for four-level solid-state laser systems. It is shown that careful control of the pump beam geometry, cavity length, and crystal length can enhance single frequency performance View full abstract»

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  • Spatial fidelity of photorefractive image correlators

    Page(s): 3025 - 3032
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    The set of equations describing photorefractive four-wave mixing of image-bearing beams has been solved in the presence of diffraction using a perturbation analysis assuming a strong uniform backward pump and a weak conjugate. To first order, it was found that the conjugate image is bilinearly related to the forward-pump and probe images. By using a Green's function approach, an analytical expression for the bilinear kernel was derived. This kernel, which governs the bandwidth of the conjugation system, is a function of the material parameters, the beam angles, and the crystal length. When a conjugator is used to determine the correlation between two images, the result was found to be a distorted version of the correlation image. This distortion was reduced when the image with the smallest extent was chosen as the forward-pump image View full abstract»

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  • Stimulated Raman scattering in methane-experimental optimization and numerical model

    Page(s): 3017 - 3024
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    The stimulated Raman effect in methane was investigated both theoretically and experimentally. An experimental setup was used to optimize the Raman conversion of a 1.06-μ laser source into a wavelength of 1.54 μm in pressurized methane. Efficient conversion (up to 45% efficiency) is accomplished when using a full-resonator configuration for the Stokes wavelength. A numerical model is introduced, describing the Raman conversion process in the backward and the forward directions. Half-resonator and full-resonator configurations are studied. The results of the numerical model are in agreement with the experimental results View full abstract»

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  • Dual-polarization, single quantum-well AlGaInP laser diode structure

    Page(s): 2738 - 2742
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    A single quantum-well Ga0.5+δIn0.5-δ P/(AlGa)0.5In0.5P laser structure is demonstrated, which can provide similar gain in both polarizations. The slightly tensile-strained quantum-well has a light-hole ground state, which gives the lowest transparency current for TM-mode gain. However, the TE-mode gain is dominant at high drive currents. The gain-current relationships have been characterized for each polarization, and found to cross at a modal gain value of 25 cm-1. Lasers whose threshold gain is near this crossover value were found to emit in either one or both polarizations, with a very wide range of polarization asymmetry possible. A simple QW gain model can be used to qualitatively describe this behavior, along with the tendency toward TE-mode emission at higher temperature 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