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Quantum Electronics, IEEE Journal of

Issue 3 • Date March 1991

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Displaying Results 1 - 25 of 70
  • Semiconductor laser stabilization by external optical feedback

    Page(s): 352 - 372
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    A report is presented on a general theory describing the effect of external optical feedback on the steady-state noise characteristics of single-mode semiconductor lasers. The theory is valid for arbitrarily strong feedback and arbitrary optical feedback configuration and spectrum. A generalized Langevin rate equation is derived. The equation is, in general, infinite order in d/dt constituting an infinite-order correction to the low-frequency weak-feedback analysis. The general formalism includes relaxation oscillations and permits analysis of the effect of feedback on the laser linewidth, frequency noise, relative intensity noise, and the relaxation oscillation sidebands in the field spectrum. The theory is applied to two important feedback configurations: the laser coupled to a single mirror and the laser coupled to a high-Q cavity.<> View full abstract»

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  • Integrated optic adiabatic devices on silicon

    Page(s): 556 - 566
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    A study of integrated optic devices based on adiabatic principles is reported. The components are a 3-dB coupler, a full coupler, a polarization splitter, a wavelength multiplexer, and two mode shape transformers. All components were fabricated from doped silica and silicon nitride films on silicon substrates. Results are given for an adiabatic full coupler and an adiabatic 3-dB coupler, an asymmetric Y-coupler for a 1.3-1.55- mu m-wavelength multiplexer, and a tapered waveguide for mode shape transformation.<> View full abstract»

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  • Reduced-confinement GaAlAs tapered waveguide antennas for enhanced far-field beam directionality

    Page(s): 687 - 695
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    Reduced-confinement tapered waveguide antennas are shown to produce reductions of >35% in the transverse far-field beam divergence for radiation emitted from GaAlAs slab waveguides, resulting in far-field beams as narrow as 8.2 degrees full width at half-maximum (FWHM) along the direction perpendicular to the wafer surface. Reduced confinement of the guided mode near the output endface is achieved using a novel molecular-beam-epitaxy growth technique to produce a longitudinal reduction in the refractive index and thickness of the waveguide film. The reduced-confinement geometry has the distinct advantage over horn antennas of being compatible with two-dimensional antenna development. A numerical simulation is used to verify and predict the performance limitations of reduced-confinement antennas. Requirements on both the amplitude and phase profiles of the electric field at the antenna output are shown to impose a stringent lower limit on the acceptable taper length for optimal antenna performance.<> View full abstract»

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  • Guided-wave optical bistability in indium antimonide thin films

    Page(s): 809 - 816
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    Various grating configurations used to obtain optical bistability in a guided-wave format are discussed and experimentally demonstrated using indium antimonide planar waveguides. The theory of nonlinear diffusive distributed input grating coupling, is presented. The enhancement afforded by additional feedback mechanisms is verified, both with an externally coupled counterpropagating beam and with an integrated optics Bragg reflector.<> View full abstract»

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  • Nonlinear semiconductor Bragg reflection waveguide structures

    Page(s): 824 - 829
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    The waveguiding properties of finite Bragg reflection waveguides have been investigated in both linear and nonlinear regimes. The guiding properties of both linear and nonlinear BRWs have been shown to depend quite sensitively upon the core layer dimension. A feature of the analysis of the nonlinear case has been the use of Jacobian elliptic functions of complex modulus and argument to give an analytic prescription of the optical field. With structures incorporating a defocusing nonlinearity, it has been shown that BRWs may be optical-intensity tuned to support bound modes. For optical nonlinearities typical of III-V semiconductors, the threshold optical power required to access guided bound modes can be provided by diode lasers.<> View full abstract»

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  • Radiation induced gas-dynamic refractive index changes in an iodine laser oscillator

    Page(s): 459 - 464
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    Due to the exothermic recombination of ground state iodine atoms I with free radicals C3F7 to the parent molecule C 3F7I, the gaseous medium of an iodine laser oscillator is subject to spatially inhomogeneous heating. This causes temperature and pressure gradients leading to gas-dynamic motion and thus to density and refractive index changes perturbing the optical quality of the laser medium. Since the strength of the recombination reaction depends directly on the laser intensity via the process of stimulated emission, this coupling can lead to self-termination of the laser radiation. This phenomenon is experimentally and theoretically investigated View full abstract»

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  • GEO modules as a natural basis for all-optical fiber logic systems

    Page(s): 843 - 848
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    A generalized exclusive-OR (GEO) module is closely related to the physics of ultrafast, all-optical, soliton-based fiber logic gates. The authors show that a GEO module is Boolean and connectivity complete for a time-division multiplex system. Counters, time slot interchangers, AND gates, and NOR gates can be constructed from two to four GEO modules. For telecommunications, GEO modules can be used to demultiplex data, decode address headers, and provide rapid access to the network. Since GEO modules lead to minimal component implementation of some fundamental functions, they may be the natural basis for designing fiber-based logic systems View full abstract»

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  • Anomalous gain in an isotopically mixed CO2 laser and application to absolute wavelength calibration

    Page(s): 465 - 470
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    Measurements are reported on a grating-tuned CO2 laser, containing an isotopic mixture of 16O12C16 O, 16O12C18O, and 18O 12C18O. The P6 and R 14 lines of 16O12C16O were found to have anomalously high intensities. These anomalies are produced by the near coincidence of the transition frequencies in two distinct isotopes, permitting them to act as a single indistinguishable population. These two lines can be used to identify the rotational quantum numbers in the P and R branch spectra, thereby permitting absolute wavelength calibration to be achieved View full abstract»

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  • High repetition rate, wide-aperture KrF lasers for subpicosecond amplification

    Page(s): 441 - 447
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    A high repetition rate, wide-aperture KrF laser with a magnetic switch has been developed. A dynamic response and a core loss of several magnetic materials were measured, resulting in a loss as low as 0.45 J/pulse for a voltage risetime of ~100 ns. A maximum output energy of 2.5 J in 20 ns (FWHM) was obtained with a total efficiency of 2.5% at 20 Hz. The cross section of the output beam was 65×50 mm2. Spectral, spatial, and temporal profiles of gain and absorption coefficients were also measured, resulting in a peak gain of 8.5%/cm. An output energy of 410 mJ was extracted in 280 fs with two beams by using this laser as an amplifier View full abstract»

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  • Polarization independent Ti:LiNbO3 switches and filters

    Page(s): 602 - 607
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    Integrated optic polarization independent switches on X-cut Ti:LiNbO3 are realized. An interferometric switch on X-cut Z-propagating LiNbO3 utilizes passive polarization independent intersecting waveguide 3 dB couplers. Polarization independent switches on X-cut Y-propagating LiNbO3 based on polarization converters and intersecting waveguide couplers designed as passive polarization splitters are fabricated and investigated. Devices with an extinction ratio of 25 dB and low fiber coupled insertion losses of <5 dB are presented View full abstract»

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  • A more accurate analysis for the coupling between two rectangular dielectric waveguides laid in different layers

    Page(s): 538 - 542
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    The coupling characteristics of crossed-over rectangular dielectric waveguides laid in different layers are analyzed using the coupled-mode theory with the individual waveguide modal fields obtained from solving the corresponding exact boundary-value problem. The results agree with experimental data reported earlier. By comparing these data to previous analyses which employed approximate field expressions. it is found that using more accurate modal fields for the individual waveguides is essential in achieving correct prediction from coupled-mode analysis. In the case considered, the mode overlap integral which describes the crosstalk between the waveguides is found to be small so that the differences in the coupling strength as predicted by the conventional coupled-mode theory and the new theory are negligibly small. It is shown that when the conventional theory is applied, the mode overlap integral has to be included in the calculation of the coupled power in order to better explain the measured results View full abstract»

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  • Modeling and optimization of traveling-wave LiNbO3 interferometric modulators

    Page(s): 608 - 617
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    The characteristics of high-speed LiNbO3 electrooptic interferometric modulators/switches are discussed from the viewpoint of optimization of device performance. Specific calculations of the impedance, effective microwave index, and microwave attenuation parameter are presented as a function of the microwave electrode parameters including the buffer layer thickness. The authors have found that the optimization procedure is considerably simplified when the range of electrode and microwave parameters that satisfy a given bandwidth requirement is first determined View full abstract»

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  • Numerical investigation of ultrahigh frequency polarization self-modulation in semiconductor lasers

    Page(s): 389 - 395
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    Numerical simulations performed show that polarization self-modulation in suitably designed semiconductor lasers into the tens of GHz frequency region should be possible. The calculations are based on a simple model developed to describe polarization self-modulation in a ring laser cavity with a traveling-wave semiconductor laser amplifier as the gain medium. A set of difference-differential equations is derived and numerically solved. Periodic oscillations in the two polarization modes are obtained as previously reported experimentally. An examination of the various parameters and their roles in maintaining this instability is also conducted. The results indicate that, in an appropriately designed semiconductor laser with a monolithically integrated intracavity TE-TM mode converter, ultrahigh frequency polarization self-modulation to at least 50 GHz should be possible View full abstract»

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  • Diffusion and propagation characteristics of buried single-mode waveguides in glass

    Page(s): 549 - 555
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    Diffusion and propagation characteristics of single-mode shallow buried planar waveguides fabricated by purely thermal back diffusion of K+ ions in soda-lime glass are presented. The refractive index profile is determined using scanning electron microscopy and theoretically modeled by a Rayleigh function after solving the diffusion equation numerically. The dispersion curves are computed by solving the Helmholtz equation with a Runge-Kutta procedure and agree well with measured mode indexes. A decrease in the birefringence of the waveguides is observed by increasing the back diffusion time. Measured propagation losses remain less than 1.0 dB/cm for short back diffusion times at a wavelength of 0.633 μm View full abstract»

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  • Dependence of refractive index on hydrogen concentration in proton exchanged LiNbO3

    Page(s): 593 - 601
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    The nonlinear relationship between refractive index and hydrogen concentration has been experimentally determined for proton exchanged LiNbO3, incorporating the effects of partial and full annealing. Complete annealing results in low-loss waveguides in the alpha phase with small surface index changes (⩽0.02). The anneal conditions needed to reach the alpha phase can be estimated using the measured temperature dependence of the anneal diffusion coefficient. A model is presented which attributes the index change in the alpha phase to the addition of hydrogen and the loss of lithium, which is consistent with experimental results View full abstract»

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  • High-speed III-V semiconductor intensity modulators

    Page(s): 654 - 667
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    A description is given of a GaAs-AlGaAs, loaded-line traveling-wave modulator which has achieved bandwidths up to 36 GHz to date with low (<6 V) drive voltage into a 50 Ω device. The loaded-line design concept is able to combine the high efficiency of vertical p-i-n-type phase modulators with a velocity-matched 50 Ω structure to obtain very high bandwidth/voltage ratios. At 1150 nm, a bandwidth of 25 GHz for Vπ=4.85 V typically represents the performance. At 1300 nm, the bandwidth is unchanged but the drive voltage is higher by the expected wavelength-ratio factor. Reduced drive voltage can be obtained without bandwidth sacrifice by choosing a wavelength close to the material band edge. Threefold enhancement in AlGaAs at short wavelength is demonstrated (lumped only, to date) View full abstract»

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  • Nd:MgO:LiNbO3 channel waveguide laser devices

    Page(s): 618 - 625
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    A report is presented on the fabrication and efficient CW operation at 1.085 μm of Nd:MgO:LiNbO3 proton-exchanged channel waveguide lasers and amplifiers optically pumped at 0.814 μm. Thresholds as low as 1.5 mW and slope efficiencies up to 34% were achieved in monolithic miniature laser devices. Up to 14 mW of output power could be achieved without observation of photorefractive damage. Diode laser pumping was also demonstrated. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power. Experimental results were analyzed with the use of a mode overlap formalism and a value of 0.93 was found for the pump quantum efficiency. Absorption spectra, fluorescence spectra, and lifetime measurements are also reported for the bulk and waveguide material View full abstract»

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  • Numerical modeling of bistable laser diodes with saturable absorbers

    Page(s): 817 - 823
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    The authors examine and compare the various numerical models commonly used in the literature for the simulation of bistable laser diodes with saturable absorbers. The models have been improved through consideration of the coupling and the interface effect between the pumped and absorbing regions. Comparisons to experimental results are presented and discussed View full abstract»

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  • A monolithic long wavelength photoreceiver using heterojunction bipolar transistors

    Page(s): 773 - 777
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    An optoelectronic integrated circuit (OEIC), consisting of a p-i-n photodetector and heterojunction bipolar transistors connected together as a transimpedance photoreceiver, has been fabricated. The monolithic photoreceiver was made from InP/InGaAs-based heterostructures and had a bandwidth of 500 MHz with a transimpedance of 1375 Ω. At a signaling rate of 1 Gb/s, the measured receiver sensitivity was -26.1 dBm at a wavelength of 1.5 μm. A dynamic range greater than 25 dB and an equivalent input noise current of 11 pA √Hz were also measured View full abstract»

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  • Symmetrical directional coupler as a wavelength multiplexer-demultiplexer: theory and experiment

    Page(s): 567 - 574
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    The simulation of a symmetrical, graded-index waveguide directional coupler as a wavelength multiplexer-demultiplexer using the effective index method is presented. The design considerations in terms of the parameters associated with the fabrication of the device are considered. The modeling is used to arrive at the fabrication conditions of a demultiplexer operating at 1.32/1.56 μm in Ag+-Na+ exchanged BK7 glass. The performance of the demultiplexer agrees very well with the modeling results. Crosstalk of -30 and -32 dB at 1.315 and 1.561 μm wavelength, respectively, and a total insertion loss of 1.25 dB for a 14.5 mm long device with propagation loss 0.15 dB/cm have been achieved. Lowest measured cross-power ratio is less than -40 dB at 1.315 μm View full abstract»

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  • High-speed frequency modulation and switching of tunable distributed feedback lasers with two active segments

    Page(s): 668 - 677
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    The author extends the analysis of high-speed frequency modulation in DFB lasers with two active segments. The strong FM response in such lasers is very different, in both magnitude and phase, for the red- and blue-shifted static tuning regimes. The author introduces the frequency step-response function to characterize in the time domain the dynamics of laser frequency switching from one value to another. This time domain picture shows clearly the effects of magnitude and phase variation of the FM response on the switching behavior of the laser. He defines the frequency switching speed of the laser and observes a tradeoff relation between this speed and the magnitude of the FM response, as characterized by the magnitude-speed product. The results indicate that with optimum laser parameters and operating conditions, the frequency switching rate, and thus also the frequency shift keying (FSK) modulation rate, can be extended to the multigigahertz range (>8 GHz) View full abstract»

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  • Integrated optic devices based on nonlinear optical polymers

    Page(s): 778 - 787
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    An examination is made of the state of the art of nonlinear optical polymeric materials in view of their potential advantages. It is shown that these organic materials have many attractive features compared to LiNbO3 and III-V semiconductors with regard to their use in integrated optic circuits, especially since the level of integration is ever increasing. Considering more specifically electro-optic devices, a description is given of some of the theoretical background and basic properties. These polymers have already demonstrated a very high and extremely fast electro-optic effect compared to LiNbO3. It is also shown how low-loss waveguides can be fabricated by using easy techniques such as direct UV bleaching. The performance of phase modulators, Mach-Zehnder interferometers, and 2×2 space switches built with such polymers is already very promising View full abstract»

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  • Analysis of injection-locked gain-guided diode laser arrays

    Page(s): 396 - 401
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    A new model for injection-locked gain guided laser arrays is proposed. Diffraction-limited and single-lobe operation of injection-locked arrays is attributed to coherent summation of several transverse modes that are phase locked by injection. The model predicts far-field and near-field patterns, locking bandwidth, beam-steering properties, and locked output power. The effects of varying the master power, beam shape, position, and incidence angle on the slave array facet are also studied. Theoretical and experimental results are compared View full abstract»

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  • Resonant narrowing of the nitrogen laser pulse by plasma impedance matching

    Page(s): 448 - 453
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    The plasma impedance in the spark gap and the discharge channel of a nitrogen laser with TE configuration is shown to have profound influence on the laser performance. Particularly since plasma impedance is a function of breakdown conditions, the laser pulse temporal width can be considerably minimized by adequately choosing the gas pressure. Discharge circuit analysis is compared with experimental results View full abstract»

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  • Stimulated Brillouin scattering of a KrF laser

    Page(s): 496 - 501
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    A series of experiments in which the efficiency and fidelity of SBS (stimulated Brillouin scattering) wavefront reconstruction are measured as a function of the temporal coherence, focusing geometry, and power of the laser source is described. The primary motivation of the research is to assess the potential of SBS as the basis of a high-resolution image protection system. Thus, a series of high-resolution image projection experiments using a SBS mirror is also described. It is shown that provided that the coherent length of the laser is longer than the active focal region primarily responsible for the growth of the SBS wave, high SBS reflectivities can be obtained which are independent of the Rayleigh range of the focusing system used. In addition, wavefront reconstruction fidelities having values approaching unity can be observed when using laser powers near the threshold for the SBS process 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