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Quantum Electronics, IEEE Journal of

Issue 4 • Date April 1978

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Displaying Results 1 - 18 of 18
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • A xenon ion pumped blue dye laser

    Page(s): 220 - 221
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    A pulsed xenon ion laser with an output power of 5 kW at 364.5 nm has been used as a pump source for several blue dyes. Broad-band conversion efficiencies exceed 20 percent. The use of a birefringent filter provides tunable output in the blue region of the spectrum with a bandwidth of 0.08 nm and a pulsewidth of 120 ns. View full abstract»

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  • Analytical approximation of the radiation confinement factor for the TE0mode of a double heterojunction laser

    Page(s): 230 - 232
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    An analytical approximation is found forGamma_{0}, the TE0radiation confinement factor in symmetric heterostructures, by using a combination of its asymptotes in the limits of very thin active layers and thick active layers, respectively. The exact expression forGamma_{0}is calculated and compared to the approximation formula. It is found that for any light guiding planar double heterostructure (DH) configuration the approximation is at most -1.5 percent off with respect to the exactGamma_{0}value. View full abstract»

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  • A laser augmented reaction: SF6+ SiH4→S*2+ SiF4+ HF + H2· retention of isotopic selectivity during detonation

    Page(s): 233 - 237
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    A single unfocused pulse of a free running CO2laser, area ∼ 8 cm2, initiates an explosive reaction between SF6and SiH4. This occurs at a minimum energy of 4 J [full width at half maximum (FWHM)sim 1.5 /mus] of which about one half is absorbed in an 8 cm long cell; total pressure 12 torr; 0.65 <p(SiH4)/p(SF6) < 1.8. The spectral and temporal distributions of the emitted chemiluminescence depend sensitively on the fuel to oxidizer ratio, and on the pulse energy; we investigated the range 4 → 20 J. The principal emission is due to S2(B^{3}Sigma-_{u} rightarrow X^{3}Sigma-_{g}). Transitionsupsilon' (0-4) rightarrow upsilon" (2-15)were recorded. In the3Sigma-_{u}state, vibrational temperatures range from 3000-13000 K. The luminosity peaks sharply at (SiH4)/(SF6) = 1.0 ± 0.05. On each side of the maximum of the emission versus composition curve [at (SiH4)/(SF6) ≈ 0.95 and 1.22, for a 12 J pulse] the residual SF6(0.2-0.5 percent of initial amount) is enriched in34SF6; the observed fractionation factors at these two compositions are 8 ± 2. The separation between the two sharply peaked optimum compositions appears to increase with increasing pulse energy. Preliminary results with other fuels suggest that the concurrent absorption of CO2laser radiation by the fuel, as well as a highly exothermic reaction, are pre-requisite for fine tuning of composition, injected power, and total pressure for optimum isotope fractionation. View full abstract»

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  • A sealed high-repetition-rate TEA CO2laser

    Page(s): 263 - 274
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    A compact atmospheric pressure CO2laser utilizing a double-discharge technique has been constructed and operated at repetition rates to 100 pulses/s. With the addition of small amounts of hydrogen and carbon monoxide to give a gas mixture of He:N2: CO2:CO:H2= 69.3:11:15:4:0.7, sealed operational lifetimes exceeding2 times 10^{6}pulses have been obtained. Operating in this mode, the output energy density is about 8-9 J/l at repetition frequencies of 30-40 pulses/s for input energy densities of 60-70 J/l. The operation of the sealed laser has been studied by means of mass spectroscopic measurements of the gas mixture. It has been determined that sealed operation is possible as long as the oxygen concentration is kept below 1-2 percent. It has also been found that the addition of small amounts of H2and CO will keep the oxygen concentration below 2 percent by reducing the CO2decomposition, allowing sealed operation. The experimental results are compared to the predictions of a theoretical model in which neutral and negative-ion processes have been included. The calculations indicate that when small amounts of oxygen or water are present in the discharge the negative-ion population is significantly increased and the ratio of negative-ions to electronsN_{n}/N_{e}can approach values near unity. These are the conditions under which discharge arcing was found to occur. The model also predicts that the dissociation equilibrium of the CO2can be controlled by the addition of the above concentrations of hydrogen and CO. View full abstract»

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  • Characteristics of a hollow-core distributed feedback CO2laser

    Page(s): 275 - 283
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    Using perturbation theory and a plane wave analysis, the scattering amplitudes and coupling coefficients for a planar, hollow-core, double grating distributed feedback (DFB) waveguide laser are derived. Waveguide reflectivity has been compared for a single and double grating waveguide configuration. For a waveguide dimension of 100 μm over a 10 cm length, reflectivity is enhanced from 75 percent for a single grating to 98 percent using a double grating configuration. Included in this analysis is the effect of phase relationship between the two gratings. Using this analysis a means has been devised whereby reflectivity of the DFB waveguide may be optimized during operation of the laser. With the double grating configuration, coupling is enhanced such that a greater plate separation is possible in nearly all cases. Use of a double grating allows the plate separation of the waveguide to be increased from 80 to 100 μm, reducing total waveguide loss from 15.9 to 8.1 dB/m. These results have led to a method of solving heretofore prohibitive characteristics of single grating hollow-core DFB waveguides. Formal relationships for the waveguide parameters where a double grating configuration is used have been presented for designing hollow-core DFB waveguide lasers operating at 10.6 μm. View full abstract»

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  • A purely chemical HCl laser employing transverse flow

    Page(s): 293 - 302
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    A purely chemical continuous wave HCl laser has been developed. The purely chemical production of nonequilibrium concentrations of Cl atoms is achieved by a branched chain reaction between NO and ClO2. Three modes of accomplishing the prepumping chemistry are discussed and their effects on HCl laser performance are evaluated. A transverse flow laser was operated having a maximum HCl multiline output power of 4 W and a chemical efficiency of 6.6 percent based on the total exothermicity of the pumping reaction. View full abstract»

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  • [Back cover]

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    Freely Available from IEEE
  • Pulse propagation in the amplifier of a high-power iodine laser

    Page(s): 302 - 309
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    Pulse propagations in an amplifier in the case of the photodissociation iodine laser are investigated with the use of semiclassical treatments, especially when the input pulse fed into the amplifier has a width comparable to or shorter than the transverse relaxation time of the amplifier medium. In our semiclassical equations for pulse propagation in an iodine amplifier, the populations of all hyperfine levels [2P1/2(F= 3, 2),2P3/2(F = 4, 3, 2, 1)], the polarizations of optically allowed transitions (DeltaF = 0, pm 1), and the Doppler detuning effects were taken into consideration. Based on the numerical integrations of the semiclassical equations, the propagated pulse shape and the population distributions of the hyperfine levels are discussed. From our calculations, it has been made clear that bandwidth limitations of pulses in the range of pulsewidths of 0.1 ns and below can be avoided by making use of the nonlinear amplification that results from the coherent interaction between the propagated pulse field and the amplifier medium. View full abstract»

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  • Modal analysis of strip-loaded diffused optical waveguides by a variational method

    Page(s): 259 - 263
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    The propagating modes supported by strip-loaded three-dimensional diffused optical waveguides are analyzed in detail theoretically by using a variational method. Some typical numerical examples of the propagation constants and the field distributions are illustrated. The dependence of propagation characteristics on the geometrical parameters of the loading dielectric strip is discussed. View full abstract»

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  • Improved coupled mode analysis of corrugated waveguides and lasers

    Page(s): 245 - 258
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    Corrugated waveguides and lasers in resonant and non-resonant situations are analyzed by an improved coupled mode theory based on a set of the coupled mode equations for guided modes and radiation continuum. The distributed feedback (DFB) coefficient and the radiation loss coefficient are given in closed forms. The formulation can be applicable to arbitrarily shaped gratings and multilayer waveguide structures. The accuracy of the theory is examined by comparing it with Tamir's exact calculation for a nonresonant situation and also with Streifer's one for a DFB structure. Reasonable accuracy is obtained by the proper choice of the unperturbed waveguide parameter. The dependence of the two coefficients on the grating depth, the grating period, the guide layer thickness, and the refractive index difference between core and cladding layers is obtained for all Bragg orders up to the fourth, and for four typical grating shapes, namely, for rectangular, sinusoidal, symmetric triangular, and sawtooth gratings. Both the threshold gain of DFB lasers utilizing higher order Bragg reflection and the output coupling efficiency of grating beam couplers are also calculated for these parameters. A new multilayer structure for controlling the radiation loss is proposed and analyzed. This structure is suitable for the suppression of the radiation loss in DBR reflectors as well as for the improvement of the output coupling efficiency in grating beam couplers. View full abstract»

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  • Laser initiated explosions and chemiluminescence

    Page(s): 237 - 245
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    Explosions can be induced in mixtures of SF6with appropriate fuels, by a single pulse of a free running CO2laserapprox 1.5 mus [full width at half maximum (FWHM)]. A typical threshold for initiation of reaction was somewhat above 4 J for a 1:1 mixture of SF6and SiH4, at a total pressure of 10 torr, with the unfocused beam illuminating 8 cm2of cell area. High levels of luminosity were generated covering both the near ultraviolet, visible, and infrared. The spectral and temporal characteristics of the following fuels and fuel-oxidizer combinations (with SF6present) are summarized: the most prominent emitter from SiH4is S*2, B3Sigma-_{u}; Sn(CH3)4+ N2O [SnO*; SnF*] ; Pb(CH3)4+ N2O [PbO*; PbF*; PbS*] ; Bi(CH3)3+ N2O [BiF*]; B2H6with and without N2O [BO*; BO*2; S*2]. Several atomic lines were also recorded. Estimates of the energy density deposited by the laser pulse suggest that initiation of rapid reaction was primarily due to attack of superexcited SF6by highly reducing radical species. View full abstract»

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  • Temporal compression of light

    Page(s): 310 - 315
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    The 5890 Å output from a CW dye laser was converted into a train of 0.5 ns pulses by frequency modulation and passage through a near-resonant atomic vapor delay line of Na. The theory of the process is discussed in both the time and frequency domains. Using a modulation index of 120 at a frequency of 17.8 MHz, we obtained values for the temporal compression ratio and intensity enhancement of 112 and 14, easily the largest that have been reported. View full abstract»

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  • Gain of high-pressure CO2lasers

    Page(s): 217 - 220
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    Previous theories of high-pressure CO2gain spectra have been modified to include gain Contributions from the newly discovered 00°2 and 00°3 sequence bands. It is shown that the inclusion of these bands has important consequences for TE CO2lasers. At a pressure of 14 atm, the sequence bands typically cause a 40 percent increase in calculated gain at all frequencies. Even at pressures as low as 1 atm, the presence of the sequence lines leads to anomalous gain coefficients on many of the regular 00°1 laser lines. View full abstract»

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  • GaAs/GaAlAs diode lasers with angled pumping stripes

    Page(s): 223 - 227
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    Operation of DH GaAs/GaAlAs stripe contact lasers with stripes oriented nonorthogonally to the cleaved end facets of the laser is described. Such lasers, with misalignment angles ofsim2deg, do not exhibit "kinking" behavior to power levels greater than 90 mW/facet, and do not exhibit relaxation oscillations under pulsed operation. Data showing the dependence of laser wavelength, spectral half-width, transverse mode structure, facet reflectivity, and output beam angle on both stripe angle and pump current level are also presented. View full abstract»

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  • Extended use of the sealed HBr chemical laser by "Cl2activation"

    Page(s): 227 - 230
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    A new passivation technique, which we call "Cl2activation," has been developed for the pulsed HBr chemical laser. Hundreds of HBr laser shots have been observed from the sealed H2+ Br2gas mixture as the result of the Cl2activation. Under normal conditions, HBr molecules accumulate in the reagent gas mixture after laser oscillation, and the accumulated HBr molecules hinder subsequent laser oscillations. In Cl2activation, Cl2molecules attach themselves to the stainless steel electrodes in the pin-rod TE-type laser tube. The attached Cl2molecules react with the HBr molecules which were produced by the laser reaction. As a result, HBr molecules do not accumulate in the gas mixture. The mixture returns to its original composition after each lasing. As a maximum, about 700 laser shots have been observed. View full abstract»

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  • Far infrared laser emission from15NH3optically pumped by a CW sequence band CO2laser

    Page(s): 222 - 223
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    Two new coincidences between theP(31) andP(35) CO210.6 μm sequence band emission lines and the15NH3absorption lines have been found to produce far infrared (FIR) emission lines atlambda = 111.9and 218 μm. In addition, the known coincidence between the regularR(42) 10.6 μm band CO2emission line and theasR View full abstract»

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  • Spectroscopy and lasing of a high Nd concentration Al-phosphate glass

    Page(s): 283 - 293
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    An Al-phosphate glass containing Nd3+in concentrations ranging from3 times 10^{20}to2.7 times 10^{21}ions/cm3has been prepared and investigated spectroscopically. Different ways of measuring the4F3/24I9/2emission cross sections yield values between1.96 times 10^{-20}and2.7 times 10^{-20}cm2. At the highest concentration the decay time is 50 μs, while the radiative lifetime is estimated to begeq446 mus. Lasing experiments were performed by pumping thin platelets of glass coaxially with a dye laser. Cross sections, losses, and differential efficiencies are derived from these experiments. The status of high concentration glasses versus stoichiometric Nd compounds is reviewed. 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