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Quantum Electronics, IEEE Journal of

Issue 4 • Date April 1989

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Displaying Results 1 - 22 of 22
  • Spectral linewidth and resonant frequency characteristics of InGaAsP/InP multiquantum well lasers

    Page(s): 662 - 667
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    The spectral linewidth and resonant frequency characteristics of 1.3- mu m InGaAsP/InP multi-quantum-well lasers grown by liquid-phase epitaxy were investigated and compared to those of the conventional double heterostructure (DH) lasers. A decrease in spectral linewidth and an increase in resonant frequency f/sub r/ with decreasing well thickness were observed. Moreover, the linewidth enhancement factor alpha was reduced to approximately 2 for well thicknesses of less than approximately 200 AA, while that of the DH laser was approximately 6. An f/sub r/ of 9 GHz, which is twice as large as that of conventional DH lasers, was achieved at an optical power of 5.3 mW/facet.<> View full abstract»

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  • Coupled phase-shift distributed-feedback semiconductor lasers for narrow linewidth operation

    Page(s): 678 - 683
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    Mode properties of a coupled phase-shift distributed-feedback (DFB) structure are analyzed and the feasibility of narrow-linewidth emission is shown theoretically. The structure consists of a multiple number of phase-shift DFB laser units which are arranged in tandem and coupled with each other through additional phase shift of corrugation. Optimum structure parameters were determined for two coupled laser units so that the frequency detuning is zero and the mode pattern is the flattest. The mode analysis shows that the intensity distribution is flatter and the normalized coupling constant can be larger than those for the conventional DFB laser with a single phase shift. This indicates that the cavity length can be extended with less influence from the longitudinal spatial hole burning effect.<> View full abstract»

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  • High-power high-efficiency GaAlAs superluminescent diodes with an internal absorber for lasing suppression

    Page(s): 696 - 704
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    The operation principles of a high-power high-efficiency GaAlAs superluminescent diode based on an internal absorber for lasing suppression is described. The absorber is based on an unpumped/reverse-biased section in the device, and the superluminescent diode characteristic depends heavily on the bias condition of the absorber section. The very high efficiency of the device arises from the strong waveguiding effect of the buried heterostructure. A theory which accurately describes the various device characteristics is described.<> View full abstract»

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  • Gain spectra of quantum wires with inhomogeneous broadening

    Page(s): 705 - 712
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    The effects of fabricational variations on the gain spectra of quantum wires are calculated within the limits of first-order perturbation theory. Gain spectra and density of states for 50-AA-radius and 150-AA-radius cylindrical quantum wires are calculated and plotted for several different fabrication tolerances. The wave functions for a finite, cylindrical potential are calculated and a quasicritical radius, below which the carriers are weakly confined by the potential, is established. This sets a lower limit on quantum wire size. Upper limits on the size of quantum wells, quantum wires, and quantum boxes are also discussed. The threshold current and differential gain of quantum-wire lasers and quantum wire array lasers are calculated. These calculations indicate a possible reduction in threshold current of one to two orders of magnitude as compared to the best quantum-well lasers.<> View full abstract»

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  • Voltage-induced optical waveguide modulator in lithium niobate

    Page(s): 720 - 728
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    A type of optical modulator first proposed by D.J. Channin (1971) in which an optical waveguide is induced in an electrooptic substrate by applying voltage between two parallel coplanar electrodes is reinvestigated. It is found that such devices will work for voltages much smaller than those used by Channin. The devices are fabricated with much smaller gaps between the electrodes and have an optical buffer layer to isolate the optical field from the electrodes. The theory of operation is developed and the device is modeled mathematically. The theory predicts that the optical field distributions of the modes of these devices become more highly confined with increasing voltage.<> View full abstract»

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  • Further evidence of strong coupling effects in three-arm Ti:LiNbO/sub 3/ directional couplers

    Page(s): 729 - 735
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    The switch characteristics of three-arm integrated optic directional couplers with both symmetric and antisymmetric drive voltages are examined. The symmetry properties of these devices, predicted by previous theory, are shown to be violated and the reasons for this are discussed in terms of scalar strong coupling coefficients normally neglected as small. It is also shown that the inclusion of modal overlaps introduces additional coupling terms and causes significant power redistribution in the bend sections. Experimental measurements for the antisymmetric configuration are presented, and it is shown that different electrode loading of the center and outer guides affects device operation.<> View full abstract»

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  • The effect of wavefront tilt on mode conversion in asymmetrical Y-branch waveguides

    Page(s): 742 - 748
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    Step approximation models provide a simple method of studying mode propagation and mode conversion in planar Y-branch optical waveguides. They are, however, only applicable to small branching angles since they neglect the wavefront tilt of the separating waveguides. A phasefront tilt approximation which can be used in conjunction with the local normal mode profile of the five-layer structure is introduced. By rotating the Y-branch about the branching point, a symmetrical branching angle is defined so that the phasefront approximation can be used not only for symmetrical Y-branches, but also for Y-branches which have an asymmetrical branching angle or have a change in branching angle along the longitudinal axis of the Y-branch.<> View full abstract»

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  • Anisotropic aberrations in planar waveguide lenses

    Page(s): 749 - 754
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    An approximate analysis of anisotropic aberrations in waveguides lenses on lithium niobate is presented. The causes of anisotropic aberrations are discussed. Anisotropic aberrations of a single refracting surface are studied and a general expression for an optical system consisting of m surfaces is derived. Numerical examples provided illustrate the anisotropic aberrations in various spherical aberration-corrected waveguide lenses.<> View full abstract»

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  • Eigenpolarization theory of monolithic nonplanar ring oscillators

    Page(s): 767 - 790
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    Diode-laser-pumped monolithic nonplanar ring oscillators (NPROs) in a applied magnetic field can operate as unidirectional traveling-wave lasers. The diode laser pumping, monolithic construction, and unidirectional oscillation lead to narrow linewidth radiation. Here, a comprehensive theory of the eigenpolarizations of a monolithic NPRO is presented. It is shown how the properties of the integral optical diode that forces unidirectional operation depend on the choice of the gain medium, the applied magnetic field, the output coupler, and the geometry of the nonplanar ring light path. Using optical equivalence theorems to gain insight into the polarization characteristics of the NPRO, a strategy for designing NPROs with low thresholds and large loss nonreciprocities is given. An analysis of the eigenpolarizations for one such NPRO is presented, alternative optimization approaches are considered, and the prospects for further reducing the linewidths of these lasers are briefly discussed.<> View full abstract»

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  • Kinetic processes in electron beam-excited XeF (C40aA) laser media

    Page(s): 791 - 802
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    Fundamental processes affecting the operation and performance of electron beam-excited XeF(C to A) laser media have been analyzed and modeled. Emphasis has been placed on conditions typical of high current density ( approximately 250A cm/sup -2/), short pulse ( approximately 10 ns FWHM) e-beam excitation of high pressure ( approximately 6 atm) multicomponent mixtures comprised of Ar-Kr-Xe-NF/sub 3/-F/sub 2/. Computation of the temporal evolution of excited and ionized species for such circumstances has permitted identification of the factors controlling XeF(C) formation and loss, and has resulted in the identification of the primary transient species that absorb radiation in the blue-green spectral region. The data so obtained serve to explain measured XeF(C to A) properties, particularly net gain, under conditions for which the C to A laser energy density and efficiency values are comparable to those of the UV XeF(B to X) laser.<> View full abstract»

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  • Reflection matrix for Gaussian light beams in FEL oscillators

    Page(s): 803 - 816
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    The transformations of Gaussian radiation beams caused by reflection off mirrors is an important issue for the operation of free-electron lasers as oscillators. The reflected radiation from a single incident Gaussian mode will contain other modes due to the finite size, the deflection of the beam, and mismatches in the curvature. A method for analytic computation of the reflection matrix is developed. The mirror surface that reflects spherical incoming wavefronts into spherical outgoing is determined analytically. The cross coupling among vector components of the radiation field, caused by the curvature of the mirror surface, is included.<> View full abstract»

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  • Subpicosecond laser timing stabilization

    Page(s): 817 - 827
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    The 0.25 Hz-25 kHz pulse timing fluctuations of a Nd:YAG CW-mode-locked laser are reduced from 20.6 ps to less than 0.30 ps rms by an electronic phase-lock loop. Stabilizer design considerations include the laser phase control characteristics, phase detector additive noise, and spurious detection of the laser amplitude noise by the loop phase detector. Applications include synchronization of multiple picosecond pulsed lasers, and synchronization of lasers and electronic signal sources in picosecond physical measurements.<> View full abstract»

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  • Efficient compression of high-energy laser pulses

    Page(s): 828 - 835
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    Limitations caused by stimulated Raman scattering (SRS) for laser pulse compression in traditional fiber-grating compressors are discussed. It is shown that the scheme utilizing fibers of length L exceeding the length of the dispersion walk off L/sub walk/ /sub off/ of pump pulses and SRS permits one to obtain high-contrast compressed pulses, their energy being no more than a few nJ, and the ultimate width being proportional to the square root of the initial pulse width. For the compression utilizing fibers of length L> View full abstract»

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  • Silent-discharge excited TEM/sub 00/ 2.5 kW CO/sub 2/ laser

    Page(s): 836 - 840
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    The performance characteristics of the TEM/sub 00/ 2.5-kW silent-discharge-excited, transverse-flow CO/sub 2/ laser are presented. The silent-discharge excitation is advantageous for a high-quality beam pattern and for pulsed operation and sealed-off operation. Furthermore, the discharge power can be easily increased without limitation due to the instability of the discharge itself.<> View full abstract»

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  • Photoinduced conversion of radiation polarization in integrated optics components based on LiNbO3

    Page(s): 736 - 741
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    Two photoinduced effects in LiNbO3 optical waveguides (unidirectional waveguide mode conversion from ordinary to extraordinary polarization and radiation coupling out of waveguides with polarization plane rotation) are discussed. The circular photovoltaic tensor component in LiNbO3 is determined experimentally, and a photovoltaic mechanism to explain photoinduced radiation coupling out of waveguides is proposed. The impact of the effects discovered on the performance of phase modulators is discussed View full abstract»

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  • Y-junction and misaligned-stripe diode laser arrays with nonuniform reflective diffraction coupler

    Page(s): 689 - 695
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    The Y-junction structures are analyzed using diffraction theory based on a scattering-matrix representation. In the analysis, the threshold behavior, mode distribution, and stability of the array modes are calculated as a function of various array structures. The oxide-restricted ridge waveguide laser is chosen as the basic laser structure and a simple fabrication process is developed. The output peak-power per facet for a 10-element Y-junction array without coating is over 800 mW and the total differential quantum efficiency reaches 70%. The misaligned-stripe laser exhibits high power of 500 mW per facet and high quantum efficiency of 60%. The fundamental mode operation is achieved for both lasers View full abstract»

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  • Optical reflectometry with micrometer resolution for the investigation of integrated optical devices

    Page(s): 755 - 759
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    An optical time-domain reflectometry (OTDR) system using an infrared subpicosecond pulse source in conjunction with balanced heterodyne detection is discussed. Experimental results show a density of more than 100 dB and a resolution of 60 μm in air. Taking advantage of the large tuning range of the laser system, it is possible to improve the resolution to less than 10 μm. The applicability of the OTDR system for the diagnostics of integrated optical devices is demonstrated for a simple GaAs waveguide structure View full abstract»

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  • Photoelastic effects on the emission patterns of InGaAsP ridge-waveguide lasers

    Page(s): 651 - 661
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    The dielectric window opening in ridge waveguide lasers needed for the ohmic contact is shown to be able to cause appreciable stress deformations of the effective permittivity which defines the waveguide properties of the laser. For edge force values in the range of 40 dyn/μm, the emission properties of the laser, namely the near field and the threshold current, start to change. The results indicate that for still higher values, filamentation begins to occur. The numerical results presented use a global self-consistent model of the semiconductor laser and finite-element method for stress-field calculations View full abstract»

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  • Modeling of longitudinally pumped CW Ti:sapphire laser oscillators

    Page(s): 760 - 766
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    Longitudinal pumping of CW Ti:sapphire oscillators is considered to predict the power output of such oscillators using folded, astigmatically compensated cavities. The model predicts how the oscillator performance is affected by the selection of Ti3+ concentration, material figure of merit, rod length, and pump and cavity mode waists. Experimental results for broadband CW oscillators pumped by CW argon ion lasers are reported, and these are shown to be in excellent agreement with theory. Nearly 30% slope efficiency is achieved with a four-mirror folded cavity and even higher efficiencies are predicted for optimized pumping View full abstract»

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  • Effect of 1/f-type FM noise on semiconductor-laser linewidth residual in high-power limit

    Page(s): 684 - 688
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    The FM-noise spectrum and the linewidth of 1.3 μm DFB (distributed feedback) semiconductor lasers measured in the high-power state up to 20 mW are discussed. A 5-MHz residual linewidth is observed in the high-power limit. The FM-noise spectrum consists of white noise and 1/f noise. The spectral density of the white noise is reduced by the increase in the output power, whereas that of the 1/f noise is unchanged, which means that the linewidth residual in the high-power limit is caused by the 1/f noise rather than the white noise. The impact of the 1/f-type FM noise on coherent optical communication systems is also discussed View full abstract»

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  • The effect of band-tails on the design of GaAs/AlGaAs bipolar transistor carrier-injected optical modulator/switch

    Page(s): 713 - 719
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    The variations in the absorption coefficient and the refractive index in the waveguide region of a double-heterostructure N-AlGaAs/p-GaAs/N-AlGaAs bipolar transistor carrier-injected optical modulator/switch are calculated theoretically using a band-tail model. The refractive index change is calculated by a Kramers-Kronig analysis of the absorption curve, which changes in the vicinity of the absorption edge primarily because of the effect of band-filling, band-gap shrinkage, and plasma dispersion associated with the presence of free carriers. The performance of bipolar transistor carrier-injected optical modulator/switch is analyzed on the basis of the calculated results, including the alpha-parameter and the maximum modulation depth. It is shown that small frequency chirping and high modulation depth with low absorption loss can be achieved by properly selecting the optimum operating conditions View full abstract»

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  • Linewidth of laser diodes with nonuniform phase-amplitude α-factor

    Page(s): 668 - 677
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    The linewidth of a laser diode having a phase-amplitude factor α that varies arbitrarily along the path is calculated. For simplicity, an ideal single-mode ring-type laser diode with only one wave circulating is considered. The theory is exact in the limit of large injected currents, provided parameters such as the carrier temperature do not vary and the gain or loss per wavelength is small. It is found that when the electron-hole pairs are injected independently of each other (that is, when the pump fluctuations are spatially uncorrelated shot noises) the linewidth is half the value obtained earlier for the linear regime multiplied by (1+α2)av where the round-trip averaging is affected with respect to the reciprocal of the power gain. Specific examples, in particular a sequence of amplifiers and partially reflecting mirrors, are considered 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