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Quantum Electronics, IEEE Journal of

Issue 9 • Date Sep 1991

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Displaying Results 1 - 19 of 19
  • Ultrathin harmonic generators

    Page(s): 2170 - 2181
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    The author analyzes harmonic generation in ultrathin media to evaluate their materials requirements. It is shown that in such devices the conversion efficiency to the second harmonic is necessarily limited to about 25%, because higher harmonics are also necessarily generated with significant efficiencies. Ultrathin devices are therefore subject to large thermal loads, and perhaps optical damage arising from the generation of strong ultraviolet or soft X-ray harmonics. Whereas ultrathin media are not as efficient as conventional phase-matched crystals for second-harmonic generation, they do generate phase-coherent, multiple higher harmonics. As a consequence, they can generate optical square waves and electromagnetic shock waves, and may find application as coherent soft X-ray generators View full abstract»

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  • Mode locking of a Nd:YAlO3 laser at 1.08 and 1.34 μm wavelengths using a single LiIO3 crystal

    Page(s): 2135 - 2141
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    Passive mode locking of a Nd:YAlO3 laser at 1.08 and 1.34 μm using a nonlinear mirror based on second harmonic generation is described. A single 30° cut frequency-doubling LiIO3 crystal was used to mode lock both transitions, demonstrating the superiority of this mode-locking technique over that using saturable absorbers. Pulses as short as 50 ps at 1.08 μm and 15 ps at 1.34 μm were obtained. A comparative analysis of the mode-locking performance at the two fundamental wavelengths is presented, indicating that the longer pulse duration at 1.08 μm is due to the higher gain and an insufficient number of round-trips in the pulse train development View full abstract»

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  • Theory of amplitude and phase effects in 2-D-two-wave mixing

    Page(s): 2193 - 2200
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    The two-wave mixing process in a photorefractive medium is investigated including nonuniform amplitude distributions of the pump and signal waves, plane-aberrated phase fronts, absorption, and arbitrary grating phase shift φ. The resulting system of two-dimensional coupled-wave equations is solved numerically with the aid of a two-dimensional Runge-Kutta method. Numerical data are shown to explain the gain distributions and image distortion properties in photorefractive amplifiers of the crossed beam, transmission and reflection grating type. A simple relation is presented describing the amplitude-phase crosstalk in two-wave mixing. One example is illustrated showing the possibility for compensating for aberrations using special pump and/or signal beam profiles with a grating phase shift different from 90° View full abstract»

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  • Laser and spectral properties of Cr, Tm, Ho:YAG at 2.1 μm

    Page(s): 2142 - 2149
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    The authors study the loss process in a uniformly pumped amplifier experiment. The impact of the loss mechanism on laser performance is discussed and its dependence on excited state density is considered. An extensive set of measurements was performed on flashlamp pumped YAG crystals doped with chromium, thulium, and holmium. Near-room-temperature laser operation on the 2.1 μm holmium transitions was characterized using a frequency selective resonator. Small signal gain and stored energy lifetimes were analyzed to determine the strength and dependence of loss mechanisms. The analysis of the thermal lensing experiments demonstrated a high degree of excess heat generation in this material View full abstract»

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  • Optimization of Q-switched lasers

    Page(s): 2220 - 2225
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    The authors extend the standard rate equation analysis to obtain expressions for the maximum peak power, maximum pulse energy, and minimum pulsewidth of a single Q-switched output pulse; the maximum power efficiency of a repetitively Q-switched laser; and the corresponding cavity output couplings. Results are obtained analytically and numerically, and a comparison of the two sets of results is made. As a first step in this process the authors derive general expressions for the peak power, pulsewidth, pulse energy, and power efficiency. The authors next differentiate these expressions in order to find the maxima or minima that optimize the parameter of interest. Differentiation is done with respect to the cavity output coupling View full abstract»

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  • High power, nearly diffraction-limited output from a semiconductor laser with an unstable resonator

    Page(s): 2098 - 2108
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    The authors describe an on-the-chip design of a nearly diffraction-limited broad-area semiconductor diode laser. The device achieved single lateral mode operation as unstable resonators with magnifications between two and three. The unstable resonators were realized by focused ion beam (FIB) micromachining a diverging mirror at one of the outcoupling facets. The modeling efforts agree well with experimental data and show that an optimum device design exists in which stable nearly diffraction-limited operation is predicted for up to six times threshold. This unstable resonator design has achieved, experimentally, the highest diffraction limited power and best external differential efficiency ever reported for any broad-area device with a curved facet View full abstract»

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  • A tanh substitution technique for the analysis of abrupt and graded interface multilayer dielectric stacks

    Page(s): 2086 - 2090
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    The authors report a new analytical technique for estimating the peak reflectivity of lossless dielectric stacks with combinations of quarter and/or half-wave thicknesses. A simple variable substitution is used to transform the standard formula for the reflectivity of a Fabry-Perot resonator into a remarkably simplified form. The resulting expressions for reflectivity are intuitively appealing, allowing use of additive algebra to calculate the peak reflectivity of a multilayer dielectric stack View full abstract»

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  • Single-mode pulses from a high-pressure CO2 laser operated below emission threshold

    Page(s): 2226 - 2231
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    The authors describe a simple modification to the injection seeding method which has proved experimentally to yield reliable, single-mode emission from a 10-atm CO2 laser without the need for cavity length tuning. The technique consists of choosing the laser parameters such that the power oscillator is operated slightly below emission threshold, even though the gain can be above threshold for a short time following excitation. Under such circumstances, the initial laser power due to spontaneous emission is too weak to be amplified to a significant level during the period where the gain exceeds the losses. If a more intense external signal is injected into the laser, it can be regeneratively amplified to much higher powers, eventually extracting a substantial fraction of the available laser energy View full abstract»

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  • Integral equation analysis for first order vector correction of arbitrary profiles

    Page(s): 2159 - 2169
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    The author's semianalytical method of analysis for arbitrary weakly guiding circular and noncircular profiles based on the scalar wave equation is extended and developed to encompass the analysis of the first order vector correction for the zeroth order modes of the scalar wave equation. The method presented implements no approximations in the analysis of the first order correction and retains all the properties of the semianalytical method of analysis previously presented, thus resulting in a method of analysis possessing extremely high accuracy (<10-5%) View full abstract»

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  • Phase-matched harmonic generation in lithium triborate (LBO)

    Page(s): 2182 - 2192
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    The authors present refractive index, thermo-optic, phase-matching angle, nonlinear coefficient, absorption, and scattering data on lithium triborate (LBO) crystals. They briefly discuss the material quality of the crystals, including the results of calorimetric absorption measurements in the infrared and ultraviolet. They present a new set of refractive index values with better than fourth decimal place precision, as well as measurements of the thermo-optic parameters. The nonlinear coefficients and other frequency conversion parameters of LBO were investigated by studying the phase-matched generation of Nd:YAG harmonics. These results are summarized. The authors discuss angular and thermal bandwidths for phase matching. Finally, they compare the efficiency of LBO with that of several other frequency conversion crystals for a common commercial application-the generation of Nd:YAG harmonics View full abstract»

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  • A theoretical analysis of linewidth broadening in frequency tunable DBR lasers

    Page(s): 2109 - 2115
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    Linewidth broadening in frequency tunable distributed-Bragg-reflector (DBR) lasers with tuning sections is analyzed. The analysis is based on a simplified two-section single-mode cavity model and quantum mechanical Langevin treatment. The origin of linewidth broadening is shown to be low frequency excess FM noise caused by carrier fluctuation in the tuning section. A scaling law, which permits optimal device parameter design, is then derived. When a decrease in the carrier lifetime is combined with an increase in the tuning current, linewidth broadening can be suppressed without frequency tuning range reduction View full abstract»

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  • Possibility of X-ray detection using quantum wells

    Page(s): 2116 - 2121
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    The author presents simple designs of quantum-well-based detectors which can be easily fabricated and which can detect a flux of X-rays incident on the detector. The author calculates the X-ray induced change in absorption and refractive index in GaAs-based quantum wells and uses that information to predict the performance of several proposed X-ray detectors based on carrier induced change in optical susceptibility in semiconductor quantum well structures following X-ray absorption. A 1% change in the probe beam in a reflection geometry is calculated for an incident flux of 12 X-ray photons per μm2 View full abstract»

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  • Efficiency and threshold pump intensity of CW solar-pumped solid-state lasers

    Page(s): 2129 - 2134
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    The authors consider the relation between the threshold pumping intensity, the material properties, the resonator parameters, and the ultimate slope efficiencies of various solid-state laser materials for solar pumping. They clarify the relation between the threshold pump intensity and the material parameters and the relation between the ultimate slope efficiency and the laser resonator parameters such that a design criterion for the solar-pumped solid-state laser can be established. Among the laser materials evaluated, alexandrite has the highest slope efficiency of about 12.6%; however, it does not seem to be practical for a solar-pumped laser application because of its high threshold pump intensity. Cr:Nd:GSGG is the most promising for solar-pumped lasing View full abstract»

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  • Dark spatial soliton propagation in bulk ZnSe

    Page(s): 2211 - 2219
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    The propagation of dark spatial solitons was experimentally demonstrated in bulk ZnSe at λ=532 nm using a picosecond laser system. Several propagation and collision parameters were measured and compared with analytic and numerical predictions. It is shown that the propagation parameters behave in a manner consistent with two-dimensional analytic and three-dimensional numerical predictions. The important result is that it is possible to create pronounced dark spatial solitons on a bright optical pulse which do not disappear due to the self-defocusing and diffraction processes operating in the media of interest View full abstract»

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  • Output energy characteristics of optimally pumped rotating mirror Q-switch lasers

    Page(s): 2094 - 2097
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    The author develops a simple analytical formula for the key laser resonator and Q-switch parameters of an optimally pumped rotating mirror Q-switch laser. The analytical expression developed relates the maximum attainable single pulse output energy to the laser parameters such as rotating mirror speed, output mirror reflectivity, length of the resonator, and the absorption cross section of the laser media on the basis of the experimentally measured mechanical Q-switch loss form. Good agreement between theory and the output performance of a test Nd-glass laser has been demonstrated View full abstract»

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  • Time-resolved switching characteristic of the nonlinear directional coupler under consideration of susceptibility dispersion

    Page(s): 2150 - 2158
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    Two new forms of nonlinear coupled mode theory are presented which allow a quantitatively correct calculation of the temporal and spatial field evolution in a nonlinear coupler. The resultant set of coupled equations for the Fourier transforms of the pulse envelopes of the basis functions are numerically solved for representative coupling and excitation conditions. The approach permits the treatment of the power and time dependent switching characteristics of ultrashort pulses by accounting for the frequency dependence of the susceptibilities and coupling integrals. The results show that switching efficiency is low in the positive dispersion region due to pulse breakup. The pulse breakup can also be observed in the negative dispersion region, with pulses representing higher order solitons having a peak power on the order of the continuous-wave switching power View full abstract»

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  • Electric field effects in AlGaAs-GaAs symmetric and asymmetric coupled quantum wells

    Page(s): 2122 - 2128
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    A theoretical study of energy level shift and field-induced tunneling in symmetric and asymmetric coupled quantum wells is presented. Energy level shift is calculated from the time-dependent Schrodinger equation using the inverse power method. The time evolution of an electron wavepackage is shown by the application of the time-development operator of the time-independent Schrodinger equation. Energy level shift in coupled quantum wells is found to be enhanced in comparison to single quantum wells. The energy level shift in coupled quantum wells is found to be nearly linear with the applied field. Oscillation frequencies for electrons in symmetric and asymmetric coupled quantum wells are evaluated versus the applied field and compared to semiclassical prediction. Tunneling lifetimes in symmetric and asymmetric coupled quantum wells are evaluated versus the applied field View full abstract»

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  • A scheme of picosecond pulse shaping using gain saturation characteristics of semiconductor laser amplifiers

    Page(s): 2201 - 2210
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    To obtain high power, well shaped picosecond pulses from gain-switched semiconductor lasers, the use of dynamic gain saturation characteristics of semiconductor laser amplifiers was investigated theoretically and experimentally. A configuration of a reflected-wave amplifier (RWA) with single-side external coupling is introduced for pulse shaping, which is found to be suitable for enhancing dynamic gain saturation. By a combination of a distributed feedback laser oscillator at 1.3 μm in wavelength and a reflected-wave amplifier of 400 μm cavity length with asymmetric facet reflectivities of 0.01% and 30%, single-mode optical pulses with almost no tailing, full width at half maximum of 15 ps, and peak power exceeding 50 mW were obtained without pulse broadening, despite the considerable tail structure of the incident pulse View full abstract»

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  • Single-axial mode, intracavity doubled Nd:YAG laser

    Page(s): 2091 - 2093
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    A diode-pumped, single-axial mode, intracavity doubled laser has been demonstrated using a cavity consisting of only two intracavity components, a Brewster angle cut piece of Nd:YAG and a KTP doubling crystal. Up to 4 mW single-ended output power has been obtained for 260 mW incident power on the Nd:YAG. Threshold power was 31 mW of diode power incident on the YAG; thus, single-mode operation was attained at up to ~8.5 times threshold. At the highest power the laser was susceptible to multimode operation due to spatial hole burning effects but below ~5 times threshold reliable single mode operation was achievable 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