bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of liquid-crystal twist cells
Authors: Berreman Dwight W.
Published: January 2004

This paper describes a numerical method by which we have computed the change in molecular orientation with time in liquid-crystal twist cells when the applied field is changed. No small-angle approximation is made but backflow is neglected for simplicity. The general features of the results are illustrated with computations using typical elastic and viscous constants in doped MBBA, without and with a cholesteric twist term.
Laser-induced air breakdown for 1.06-μm radiation
Authors: Lencioni D. E.
Published: January 2004

The effects of dust on 1.06-μm laser-induced air breakdown for 100-nsec pulses are reported. The thresholds in clean air were measured as a function of spot size and were found to scale as λ−2 compared to the 10.6-μm results. A single 50-μm carbon particle present in the beam lowered the threshold to ≃5×109 W/cm2 —a factor of approximately 0.02 that of clean air. The fractional reduction in threshold due to dust particles was comparable to that reported for 10.6-μm breakdown.
Three-anode accelerating lens system for field emission scanning electron microscopy (II)
Authors: Kuroda Katsuhiro , Suzuki Tatsuro
Published: January 2004

The comparisons between the electronic computer data and the experimental results of the characteristics of a three-anode accelerating lens system for field emission scanning electron microscopy (FESEM) are described. Experimentally two characteristics were obtained. One of them is the relation between the accelerating voltages and the control voltages for the fixed working distance. The other is the variation of the current with the accelerating voltages. In comparison with the results of the electronic computer simulation, a close coincidence was found for the former case, but for the latter the experimental results are approximately half as large as those obtained theoretically.
A closer look at laser damage in PMMA
Authors: Felix M. P. , Nachbar W.
Published: January 2004

A meaningful power threshold for focused laser damage in polymethyl methacrylate (PMMA) is established. It is also shown that the type (but not the extent) of damage is identical for the Q-switched and non-Q-switched laser pulses for the range of power levels used. Finally, it is explained why the observed focused laser damage in PMMA is so much more extensive in the non-Q-switched case than in the Q-switched case, even though the latter type of laser pulse has an inherently higher peak power.
Solid-phase transport and epitaxial growth of Ge and Si
Authors: Canali C. , Mayer J. W. , Ottaviani G. , Sigurd D. , van der Weg W.
Published: January 2004

Epitaxial growth of a semiconductor film from solid solution by dissolution and transport of an evaporated semiconductor layer through a metal film has been demonstrated. A Ge growth layer of 4800 Å has been obtained by heating the system bulk-Ge/Al/evaporated-Ge at 300 °C. Electrical measurements indicate that the layers are heavily doped p type. A silicon growth of 2000 Å has been obtained by heating the system bulk-Si/Pd/evaporated-Si at 600 °C. Channeling measurements show that the Ge and Si layers are well ordered and epitaxial with the underlying substrate.
Multiline mode-locked uv-preionized CO2 laser
Authors: Richardson M. C.
Published: January 2004

A uv-photopreionized TEA CO2–N2 discharge is incorporated in an actively mode-locked CO2 laser system capable of producing individual pulses of peak power of > 200 MW with durations ∼ 1 nsec. Spectral examination of the laser output indicates that oscillation occurs simultaneously on several rotational lines of the 10.4-μ band.
Ground-state population distribution of OH determined with a tunable uv laser
Authors: Wang Charles C. , Davis L. I.
Published: January 2004

We have measured the ground-state population distribution of OH in a flame by detecting the resonance fluorescence excited by a high-power tunable uv laser beam. This technique provides spatial, temporal, and spectral resolutions which are not possible with absorption measurements involving conventional light sources. It should prove particularly valuable in studying the dynamics of combustion.
Sensitivity and fatigue of LiTaO3 for holographic recording
Authors: Spinhirne J. M. , Estle T. L.
Published: January 2004

The sensitivity of LiTaO3 crystals to hologram formation has been observed to vary with impurity concentration. For a writing wavelength of 488.0 nm and power density of 1.1 W/cm2 the sensitivity varied from a value comparable to the most sensitive doped LiNbO3 for an impure crystal to a value more than 5 orders of magnitude smaller for a purer crystal. Fatigue effects were observed upon write-erase cycling. These effects were dependent upon writing and erasure polarization and power density and could be minimized by proper choice of optical parameters.
Determination of the sign of carrier transported across SiO2 films on Si
Authors: Weinberg Z. A. , Johnson W. C. , Lampert M. A.
Published: January 2004

A technique has been developed for determination of the sign of charge carrier transported across an insulating film on a semiconductor substrate, utilizing the charge-carrier separation properties of a shallow p-n junction diffused into the semiconductor. For thermally grown SiO2, unmetallized and contacted by a corona discharge in dry air, electrons are found to carry the current for both polarities of surface potential. Also demonstrated is electron-hole pair production in the Si by electrons entering from the oxide.
Effect of crystal composition on ``quasidirect'' recombination and LED performance in the indirect region of GaAs1−xPx:N
Authors: Campbell J. C. , Holonyak N. , Kunz A. B. , Craford M. G.
Published: January 2004

The Koster-Slater one-band one-site model has been employed to investigate the modulus of the wave function of an electron bound to a N isoelectronic trap in GaAs1−xPx:N as a function of crystal composition x. The no-phonon recombination transition involving the trapped electron is enhanced as the crystal composition is changed to bring the Γ conduction band minimum, EΓ, near the N-trap level, EN. Absorption data taken on x = 1.0 and x = 0.53 GaAs1−xPx:N are consistent with the calculated increase in the probability density in the Γ region as EΓ decreases relative to EX. The change in the internal quantum efficiency as a function of crystal composition has been calculated assuming that the nonradiative component of recombination is independent of x. By weighting the internal recombination-radiation quantum efficiency by the photopic response of the eye, we have determined that the optimum range of crystal compositions in which to fabricate GaAs1−xPx:N LED's is 0.6 ≤ x ≤ 0.8. This result is in good agreement with current GaAs1−xPx :N LED fabrication processes.
Photoemission from GaN
Authors: Pankove J. I. , Schade H.
Published: January 2004

Photoemissive yield measurements were performed on degenerate n-type and semi-insulating GaN for heat-cleaned and for cesiated surfaces. The photoemissive threshold for heat-cleaned n-type material occurs at 4.1 eV, while that for semi-insulating material is beyond 5.5 eV, the experimental spectral range. From these measurements an upper and a lower limit of the electron affinity of heat-cleaned GaN is derived, namely 4.1 > χ > 2.1 eV. The threshold for cesiated surfaces on both materials is lowered to 1.5 eV, and the photoyield curve exhibits a second threshold at about 3.4 eV. The occurrence of negative electron affinity is suggested for cesiated semi-insulating GaN.
NO spectroscopy at 100 °K with a PbS0.4Se0.6 diode laser
Authors: Preier H. , Riedel W.
Published: January 2004

NO spectroscopy at temperatures up to 100 °K was achieved with a pulsed PbS0.4Se0.6 diode laser. A frequency chirping rate of about 0.3 cm−1/μs was obtained. The variation of the threshold current density and laser wavelength versus temperature is presented.
Formative time lags in CO2 laser discharges
Authors: Crawford E. A. , Phelps A. V.
Published: January 2004

Time lags for the growth of power input, i.e., formative time lags, have been measured in typical CO2 laser gas mixtures at pressures from 200 to 760 Torr using parallel plane electrodes with the 1- and 2-cm gaps illuminated by a trigger discharge. The measured time lags are about twice the values predicted using a single avalanche growth model and theoretical ionization and attachment coefficients.
Optical polarization sensitivity of lead molybdate
Authors: DeBenedictis L. C. , Lucero J. A.
Published: January 2004

The optical deflection efficiency of an acousto-optic modulator with a lead molybdate interaction medium has been measured at optical wavelengths in the region 442–1152 nm. The crystal orientation was such that the acoustic beam propagated along the optic axis and the optical beam near the a axis. The dependence of the relative figure of merit on optical wavelength and polarization has thus been determined. The results indicate that the figure of merit M2 is independent of the optical polarization at 633 and 1152 nm, but that a considerable and unexpected sensitivity to polarization occurs between 442 and 515 nm.
Intensity anomalies in the extreme VUV spectrum of Al+3 obtained in a laser-produced plasma
Authors: Valero Francisco P. J.
Published: January 2004

The results of experiments performed to check the possibility of stimulated emission in the extreme vacuum ultraviolet (VUV) by an Al+3 laser-generated plasma are reported. It is concluded that the spectral line intensity anomalies previously observed are not due to population inversion.
Comments on the distinction between ``striations'' and ``swirls'' in silicon
Authors: Ravi K. V. , Varker C. J.
Published: January 2004

The distinction between ``swirls'' and ``striations'' in silicon crystals is reemphasized. The role of swirl-nucleated stacking faults in introducing excess reverse currents in p-n junctions is distinguished from the relatively inactive nature of striations with respect to carrier recombination-generation effects. The suggestion of Yoshikawa and Chikawa of a crystal-growth-direction-dependent electric field at striations has been examined using the electron-beam-induced-current (EBIC) technique. The contrast effects observed at striations using the EBIC technique show no effects of growth-dependent electric fields.
Frequency offset of a stabilized laser due to modulation distortion
Authors: Blair D. P.
Published: January 2004

The response of a phase-sensitive detector is examined when its input signal is derived by modulation of a laser-saturated absorption line shape. Neglecting the laser background power curve, it is shown that second-harmonic distortion in the modulation gives rise to the largest laser frequency offset, 0.2% of such distortion yielding approximately 4.5 kHz frequency offset. The distortion effects are also examined when the background power curve is included.
cw dye laser for ultrahigh-resolution spectroscopy
Authors: Wu F. Y. , Grove R. E. , Ezekiel S.
Published: January 2004

Hyperfine structure in a molecular beam of I2 has been observed with a resolution of one part in 109 using a stable jet stream cw dye laser. In addition, the dye laser was long-term stabilized to six parts in 1013 by using an I2 molecular beam reference.
Increasing the effective height of a Schottky barrier using low-energy ion implantation
Authors: Shannon J. M.
Published: January 2004

The presence of a shallow n-type surface layer on a p-type substrate is shown to increase the effective height of a Schottky barrier to p-type material. The effective barrier height of Ni–Si diodes has been increased by an amount in the range 0–0.25 eV using surface layers formed by low-energy antimony implantation.
Laser emission at 3577 and 3805 Å in electron-beam-pumped Ar–N2 mixtures
Authors: Searles S. K. , Hart G. A.
Published: January 2004

Experiments were performed with electron-beam-pumped Ar–N2 mixtures. Laser emission on the second positive band transitions 3577 Å (0–1) and 3805 Å (0–2) was observed in an optical cavity fitted with Brewster angle windows. Some exciting preliminary experiments in which the laser windows were mounted at normal incidence were performed. These results indicated superfluorescent emission with an efficiency of 0.4%. The energy pathways in the irradiated mixtures were modeled and compared to the experimental results.
Intense tunable picosecond pulses in the infrared
Authors: Laubereau A. , Greiter L. , Kaiser W.
Published: January 2004

Single picosecond pulses of a Nd:glass laser are used in a single-pass generator to produce intense ultrashort infrared pulses. Starting from quantum noise, stimulated three-photon parametric amplification over ∼12 orders of magnitude is achieved in a LiNbO3 crystal at a pump intensity of 1010 W/cm2. Angular tuning provides a frequency range of 2500–7000 cm−1. High conversion efficiencies exceeding 1% are measured without crystal damage.
Comparison of H2 and HBr as cavity fuels in a cw HF laser
Authors: Cummings J. C. , Dube C. M. , Witte A. B.
Published: January 2004

H2 and HBr are compared as cavity fuels in a 1-kW arc-driven cw HF chemical laser. Closed-cavity power is presented as a function of fuel flowrate and lasing-axis position. Peak power observed was ∼350 W with HBr, ∼600 W with HBr and He, and ∼1100 W with H2. Spectral content of the laser beam indicated dominant 1–0 and 2–1 vibrational transitions with H2, and 2–1 and 3–2 transitions with HBr.
High-efficiency GaAs lo-hi-lo IMPATT devices by liquid phase epitaxy for X band
Authors: Goldwasser R. E. , Rosztoczy F. E.
Published: January 2004

n-n+-n epitaxial triple layers were grown by liquid phase epitaxy to fabricate lo-hi-lo GaAs IMPATT devices. The best diode gave 35.6% cw efficiency with 2.9-W output power at 10.4 GHz. From a group of 151 devices, 51% had better than 22% efficiency with an average output power of 2.8 W at 10 GHz. Operating voltages varied between 40 and 55 V. A theoretical efficiency of 46% was calculated for narrow spike structures using a quasistatic computer simulation.
New optical storage mode in liquid crystals
Authors: Haas Werner E. L. , Adams James E.
Published: January 2004

A novel electrically reversible storage effect in doped nematic liquid crystals is described. The ``off state'' is homeotropic nematic and the ``on state'' a single layer of densely packed spherulites. Both states are stable in time. The effect was observed in a narrow range of pitch and cell thickness combinations, and is interpreted as a nematic-cholesteric phase transition.
Atomic displacement and ionization effects on the optical absorption and structural properties of ion-implanted Al2O3
Authors: Arnold G. W. , Krefft G. B. , Norris C. B.
Published: January 2004

Ion-induced lattice atom displacements in single-crystal Al2O3 give rise to an optical absorption band at 204 nm as well as to expansion of the implanted volume. The 204-nm absorption per unit energy into atomic processes is found to increase rapidly with decreasing incident ion mass. In contrast, light ions (H+, D+, He+) show less volume expansion per unit energy into atomic processes than do heavier ions. Furthermore, the volume expansion induced by heavy ion implantation can be completely relieved by H+-ion implantation or by ionizing electron irradiation (8.16 keV). A simple model characterizes the results. The 204-nm absorption is found to be proportional to the ion energy into electronic processes, and the expansion is proportional to the ion energy into atomic processes linearly reduced by the ion energy into electronic processes. The implications for defect production in CTR insulators are discussed.
Medium homogeneity considerations in low-Mach-number flow discharges
Authors: Jacob J. H. , Legner H. H. , Ahouse D. R. , Wallace J.
Published: January 2004

Density variations in low-Mach-number (≤0.3) flowing discharges have been obtained by coupling the fluid mechanics with the plasmadynamics. The coupling occurs through the variation of the electrical conductivity with density. If this variation is known, for a particular lasing mixture, the simple and accurate analysis presented below may be applied.
Correlation of soft x-ray spots with hard radiation and neutron emission in a 1-kJ plasma focus
Authors: Schönbach K. H. , Michel L. , Fischer Heinz
Published: January 2004

One to four x-ray spots are always present in hydrogen and deuterium along the z axis during the dense pinch phase; ∼4% argon is required for pinhole photography. Spots have an observed 5–10-ns lifetime and develop in succession within the first 30 ns of the x-ray emission. The hard >80-keV radiation shows the spot time structure and controls the neutron pulse. The x-ray spots represent m = 0 plasma instabilities.
Degree of ionization of a high-temperature plasma
Authors: Hyman H. A.
Published: January 2004

An approximate method, originally proposed by Raizer for solving the Saha equations, is extended to both the corona limit, as well as to the more general, non-LTE case, in which both radiative and collisional recombination are important. The method should be useful for obtaining a reliable estimate of the degree of ionization of high-temperature high-Z plasmas.
Thermal lens effect in a binary liquid mixture: A new effect
Authors: Giglio M. , Vendramini A.
Published: January 2004

We present data showing that the thermal lens effect in a binary liquid mixture is noticeably larger than in its two pure constituents. The anomalous effect observed in the mixture is interpreted as a consequence of the buildup of thermally induced concentration gradients (Soret effect). We suggest that the thermal lens technique could be exploited for determining the thermal diffusion ratio kT in binary liquid mixtures.
Impulse produced by the interaction of CO2 TEA laser pulses
Authors: Ready J. F.
Published: January 2004

This paper describes measurements of the impulse transmitted to metallic targets by CO2 TEA laser pulses with duration around 100 ns. This represents the first such measurements for submicrosecond duration pulses. The impulse was measured as a function of target material and diameter, laser power, laser beam focusing, and ambient air pressure.
Light beam scanning and deflection in epitaxial LiNbO3 electro-optic waveguides
Authors: Tien P. K. , Riva-Sanseverino S. , Ballman A. A.
Published: January 2004

We report a method of scanning and deflecting a light beam in an electro-optic waveguide of epitaxial LiNbO3 film. The method involves the use of the electro-optic effect for excitation of a proper distribution of the refractive index which causes the light beam to deflect. The angle of deflection is found to vary continuously with the intensity of the applied field. We are able to scan a light beam in the plane of the film up to 4°. We also present a theory for the light beam deflection and show that our method does optimize the deflection efficiency.
Accumulation-mode charge-coupled device
Authors: Nelson Richard D.
Published: January 2004

An accumulation-mode charge-coupled device has been fabricated and operated at 4°K. A discussion of device energy band structure, signal-processing time, and experimental results is presented.
Velocity saturation in n-type AlxGa1−xAs single crystals
Authors: Immorlica A. A. , Pearson G. L.
Published: January 2004

Current-versus-voltage characteristics of bulk n-type AlxGa1−xAs devices are examined for material compositions 0.27<x<0.43. Preliminary experimental evidence indicates that the electron velocity saturates at a composition xs=0.38±0.02 above a threshold electric field of 2.4 kV/cm. The carrier saturation velocity is estimated to be 3.3×106 cm/sec. The direct-indirect transition of AlxGa1−xAs at 300°K, inferred from transport measurements, is estimated to be in the range 0.45–0.48.
New method to determine the photoionization threshold energy of a deep level from photocapacitance
Authors: Okumura T. , Ikoma T.
Published: January 2004

A new method is proposed to determine the photoionization threshold energy of a deep level from the dependence of photocapacitance on the scanning rate of light wavelengths. The validity is demonstrated by applying this method to minority carrier traps in an n-type GaAs and a p-type GaP. It is shown that Lucovsky's model of photoionization cross section is valid at least in photon energies less than 1.5 times the threshold energy.
Normal laser damage of silicon solar cells without phase change
Authors: Matsuoka Y. , Usami A.
Published: January 2004

An experimental study has been made of the damage to floating zone (FZ) and pulled (CZ) n/p-type silicon solar cells caused by a normal ruby laser. Although the cells were irradiated below the power density at which phase change occurred, the degradation of the normalized short-circuit current was observed mainly in the long-wavelength region. This result indicates that some kind of thermal defects are induced by laser quenching. Approximately 60–70% of the laser-induced defects annealed out at room temperature.
Short CO2 laser pulse generation by optical free induction decay
Authors: Yablonovitch Eli , Goldhar J.
Published: January 2004

Short CO2 laser pulses, adjustable in the range between 0.1 and 0.5 nsec, have been produced by a new pulse-shaping technique. A laser breakdown spark is the active switching element, but the pulse is actually generated by optical free induction decay in a passive linear medium. This approach features simplicity, fast rise time, high contrast ratio, unity switching efficiency, and is suitable as the input to high-power amplifier stages.
Polycrystalline silicon films on aluminum sheets for solar cell application
Authors: Fang P. H. , Ephrath L. , Nowak W. B.
Published: January 2004

In order to make low-cost silicon solar cells for large-scale terrestrial use, we have considered a method for growing silicon with a columnar structure, with a monograin along the growth direction. Such a polycrystal, in contrast to general polycrystal material with randomly oriented grain arrangement, would make possible polycrystalline solar cells with good photovoltaic efficiencies.
Determination of minority carrier lifetime using MIS tunnel diodes
Authors: Kar S.
Published: January 2004

A new and simple method that employs MIS tunnel diodes is described here for the determination of minority carrier lifetime in semiconductors. For large reverse bias, a direct current was measured across Si–SiO2-metal devices with oxide thickness between 40 and 60 Å. This current is the generation current in the semiconductor space-charge layer, and the lifetime is easily obtained from it.
Magnetic sensitivity of a distributed Si planar p n p n structure supporting a controlled current filament
Authors: Bartelink D. J. , Persky G.
Published: January 2004

A distributed Si planar p n p n structure has been fabricated as a magnetic field detector and has yielded output signals up to 30 times those of a comparable Hall detector. The magnetic sensitivity of the structure derives from a field-induced lateral displacement of an injected electron-hole current filament.
C3F7I photodissociation laser initiated by a CO2-laser-produced plasma
Authors: Silfvast W. T. , Szeto L. H. , Wood O. R.
Published: January 2004

Ultraviolet radiation from a CO2-laser-produced plasma in xenon has been used to obtain laser action at 1.315 μm by photodissociation of C3F7I. The relative laser output and potential efficiency of this laser excitation technique is compared to that achieved using electrical flashlamp pumping.
Mechanism and properties of point-contact metal-insulator-metal diode detectors at 10.6 μ
Authors: Twu Bor-long , Schwarz S. E.
Published: January 2004

Detection mechanisms of point-contact MIM diodes at 10.6 μ wavelength have been studied. Detailed measurements of the static current-voltage characteristic and its first and second derivatives as functions of bias voltage were made simultaneously with infrared sensitivity measurements. The results indicate that the static current-voltage characteristics extend to infrared frequencies. We find that thermal effects do not contribute significantly to detection at this wavelength, and that the tungsten whisker acts as a rather efficient receiving antenna. The antenna and its shunting capacitance apply a 3×1013-Hz ac voltage to the diode which in our experiment has amplitude 124 mV, through an impedance which is much less than the junction impedance. The diode nonlinearity d2I/dV2 varies from 6.5×10−5 to 6.7×10−3 A/V2 as dc bias increases from 0 to 300 mV. None of these conclusions apply to detection at 6328 Å; it is found that detection in the visible is dominated by thermal or photoconductive effects.
An acid treatment for raising the surface damage thereshold of laser glass
Authors: Ringlien J. A. , Boling N. L. , Dubé G.
Published: January 2004

Results of damage experiments on superpolished glass surfaces are briefly presented. It is found that polishing of glass beyond what is readily obtained by conventional polishing is not effective in increasing the damage threshold. Removal of contaminants is apparently more important, and this can be accomplished by treatment with hot nitric acid or water. The threshold can be increased by as much as a factor of 3 by using hot nitric acid. The effectiveness of the acid treatment is time dependent and the increase in effectiveness fits a diffusion model.
Toward a zero small-signal gain laser power amplifier
Authors: Schappert G. T. , Stark E. E.
Published: January 2004

We show that small-signal gain reduction in a CO2 laser power amplifier can be achieved by adding to the gain medium deuterated ammonia as a saturable absorber. The saturation energy, and effects of NH2D on the amplifier kinetics and energy extraction were also investigated.
Broadening coefficients for the P(20) CO2 laser transition
Authors: Abrams R. L.
Published: January 2004

Accurate line-shape and linewidth measurements have been made on the P(20) 10.6-μm CO2 laser transition using optoacoustic spectroscopy and a tunable waveguide CO2 laser. The absorption line shape is shown to be accurately represented by a Voigt line shape and the measured broadening coefficients are γCO2=7.61±0.10, γN2=5.58±0.20, and γHe=4.88±0.18 MHz/Torr, all measured at 298°K.
Stark cell stabilization of CO2 laser
Authors: Nussmeier T. A. , Abrams R. L.
Published: January 2004

A technique is demonstrated for locking of a GHz tunable waveguide CO2 laser to a voltage programmable absorption line in NH2D. Precision frequency control is demonstrated over the tuning range of the laser and long-term frequency stability of better than ±100 kHz is demonstrated. The advantages of the present technique are that no frequency modulation of the laser is required to generate an error signal and the laser frequency is determined by a linear relationship to the Stark cell voltage.
Separation of isotopes by laser deflection of atomic beam. I. Barium
Authors: Bernhardt A. F. , Duerre D. E. , Simpson J. R. , Wood L. L.
Published: January 2004

Spatial separation of isotopes of barium in an atomic beam has been demonstrated, using radiation pressure of light from a tunable dye laser which resolved the unusually narrow isotopic hyperfine structure of the Ba (I) 5535.7-Å resonance line. Observations of the deflected monoisotopic beam indicate an average of 25 photons scattered per atom in the deflected beam.
Monolithically integrated AlGaAs double heterostructure optical components
Authors: Reinhart F. K. , Logan R. A.
Published: January 2004

Double heterostructure waveguides with contiguous regions of varying composition and dimension in the guiding layer have been grown by a modification of conventional liquid-phase epitaxial growth procedures. This permits integration of active (lasers) and passive (modulators) optical components. Modulation of the laser intensity and envelope spectrum have been observed with a reverse bias applied to an intracavity modulator section. Low-threshold lasers have been fabricated with far-field radiation angles reduced by close to a factor of 3 over those in conventionally grown lasers.
Cross-field current-driven modified ion-cyclotron instability in an inhomogeneous magnetoplasma
Authors: Yatsui K. , Irie T. , Furumi M. , Imai T. , Yatsuzuka M.
Published: January 2004

The low-frequency interaction of a cross-field current with a longitudinally magnetized inhomogeneous plasma has been studied. It is found experimentally that, in addition to the ion-cyclotron harmonic instability, a very low-frequency instability also develops in the range ω2≪ ωc i2, ωc i being the ion-cyclotron frequency, and that at these large amplitudes nonlinear wave mixing takes place between them. Using a simple model, we show that the latter mode can be interpreted in terms of the cross-field current-driven modified ion-cyclotron instability.
Simulation of structural anisotropy and void formation in amorphous thin films
Authors: Henderson D. , Brodsky M. H. , Chaudhari P.
Published: January 2004

We have computer simulated the structure of thin amorphous films grown from a vapor. Our hard-sphere model shows that structural anisotropy and voids are a natural occurrence of the deposition process. The amount of unfilled space (voids) and the anisotropy have been studied as a function of the angle of incidence of the vapor stream upon the substrate.
Determination of the depth distribution of implanted helium atoms in niobium by Rutherford backscattering
Authors: Roth J. , Behrisch R. , Scherzer B. M. U.
Published: January 2004

Using Bragg's rule of additivity of the stopping powers in compounds and the Rutherford backscattering technique to determine electronic stopping powers, the depth distribution of 4-keV helium ions implanted in niobium was determined for different implantation temperatures.
Transferred electron photoemission from InP
Authors: Bell R. L. , James L. W. , Moon R. L.
Published: January 2004

A method of obtaining efficient photoemission in the wavelength region from 1 to 2 μm, using the transferred-electron effect in a p -type semiconductor, is proposed. Experimental demonstration of emission from InP in this mode is reported.
Multiple-pass thin-film silicon solar cell
Authors: Redfield David
Published: January 2004

A technique is described by which light entering a thin film is ``trapped'' in the sense of having to traverse the film a number of times. It is shown that the use of this technique in silicon provides a solar cell with good carrier collection efficiencies even with Si only ∼2 μm thick and with ∼10-nsec lifetime.
Narrow-band grating filters for thin-film optical waveguides
Authors: Schmidt R. V. , Flanders D. C. , Shank C. V. , Standley R. D.
Published: January 2004

Criteria and tolerances are discussed for realizing grating filters with bandwidths as narrow as 0.1 Å. Techniques are presented for minimizing the adverse effect of film thickness variations which broaden filter response and raise out of band ripple. Using these techniques a grating filter fabricated on a glass thin-film waveguide is demonstrated which has 73% reflectivity and a 3-dB bandwidth of 0.15 Å.
Generation of tunable picosecond VUV radiation
Authors: Kung A. H.
Published: January 2004

A coherent tunable vacuum ultraviolet picosecond source has been constructed by third-order nonlinear mixing of a broadly tunable picosecond visible source and the fourth harmonic of a mode-locked Nd : YAG laser in xenon. Tunable radiation in the VUV covering portions of the region from 1180 to 1470 Å and continuously from 1631 to 1946 Å is obtained.
Temperature dependence of pulsed discharge-initiated HF chemical lasers using SF6/H2, SF6/CH4, and SF6/C4H10 mixtures
Authors: Obara Minoru , Fujioka Tomoo
Published: January 2004

Energy and spectral measurements of pulsed discharge-initiated HF chemical lasers are presented. SF6/H2, SF6/CH4, and SF6/C4H10 mixtures at 228, 296, and 373 °K are considered. At the optimum pressure for each mixture, HF chemical laser output has been found to depend weakly on temperature; optimum output energy was enhanced as the initial mixture temperature was decreased. A qualitative explanation for this behavior is offered. The peak power distribution of the HF laser lines at 228 and 296 °K is also discussed.
Light-focusing plastic rod with low chromatic aberration
Authors: Ohtsuka Yasuji , Senga Takao , Yasuda Haruyoshi
Published: January 2004

Chromatic aberration of the light-focusing plastic rod (LFR) prepared by the two-step copolymerization technique of a M1-M2 monomer pair is discussed theoretically. It is found that the chromatic aberration depends on the respective optical properties of the M1 polymer and M2 polymer alone, and that the selection of a M1-M2 monomer pair is the most important determinant for low chromatic aberration. The requisites for low chromatic aberration are shown. Furthermore, we prepared a LFR with low chromatic aberration by using diethylene glycol bis (allyl carbonate) as M1 and 1,1,3-trihydroperfluoropropyl methacrylate or 1,1,5-trihydroperfluoropentyl methacrylate as M2; the chromatic aberration parameter is in good agreement with the theoretical value.
The form and stability of current-voltage characteristics for ideal thermal switching
Authors: Jackson J. L. , Shaw M. P.
Published: January 2004

Analyses of ideal models, where heat flow is restricted to one direction, result in good qualitative agreement with the current-voltage characteristics observed in materials that exhibit an abrupt change in electrical conductivity at a critical temperature, such as VO2. Stability criteria are proved for thermally induced ``S and N-shaped'' characteristics in two different geometries, where the internal current or field distributions are nonuniform.
New Si planar junction diodes with uniform avalanche multiplication
Authors: Nishida K. , Takekawa T. , Nakajima M.
Published: January 2004

Si planar diodes were obtained with a steep and deep junction except for the lateral edges. This structure was made by a single diffusion of Ga through an opening of the SiO2–Si3N4 mask. New planar diodes with unique guard rings have exhibited uniform avalanche multiplication in the broad areas, overcoming the edge breakdown. These devices are shown to be useful as avalanche photodiodes.
Electroabsorption avalanche photodiodes
Authors: Stillman G. E. , Wolfe C. M. , Rossi J. A. , Donnelly J. P.
Published: January 2004

Schottky barrier avalanche photodiodes have been fabricated on n-type high-purity epitaxial GaAs. These devices have their largest response at wavelengths beyond the usual absorption edge for high-purity materials. The absorption mechanism involves the Franz-Keldysh shift of the absorption edge, and the higher response at the longer wavelengths can be explained by a much higher ionization coefficient for holes than for electrons. The results indicate that the ratio of βp to αn is even larger than previous measurements have given.
Monte Carlo calculations of diffusion coefficient of hot electrons in n-type GaAs
Authors: Abe M. , Yanagisawa S. , Wada O. , Takanashi H.
Published: January 2004

The Monte Carlo simulation is applied to the study of the diffusion phenomenon of hot electrons in n-type GaAs. The model simulated is that the ensemble of electrons diffuses from the cathode toward the anode under the two-valley semiconductor model, repeating the accelerations by the electric field and the collisions to the phonons. This electronic diffusion includes the electron transfer diffusion between valleys as well as the thermal diffusion in each valley. The electric field dependence of the electronic diffusion coefficient determined from the present new approach almost agrees with the Ruch-Kino experimental result.
Electric field effects on biphenyl smectic A liquid crystals
Authors: Hareng M. , Le Berre S. , Thirant L.
Published: January 2004

Generally, smectic liquid crystals do not exhibit any effects when electric fields are applied. We report here a new alignment effect in a smectic A liquid crystal due to an ac electric field. This effect has been observed on several biphenyl smectic A liquid crystals. Results for the focal conic to homeotropic transition in the smectic phase are given. Several parameters-temperature, voltage, and frequency-are discussed.
Impact ionization model for dielectric instability and breakdown
Authors: DiStefano T. H. , Shatzkes M.
Published: January 2004

A mechanism describing the incipient stages of intrinsic dielectric breakdown is formulated for the case of a wide-band-gap insulator with a low hole mobility. Dielectric instability results from the tunnel injection of electrons from the cathode contact and the subsequent impact ionization and field distortion which lead to dielectric breakdown. The model, evaluated for the parameters of SiO2, predicts an intrinsic breakdown voltage which approaches a lower limit of V=9+φ for very thin films, where φ is the cathode contact barrier in volts. As a result, both the electric field at breakdown and the critical current density increase rapidly as the film thickness is reduced below 200 Å.
Transparent heat-mirror films of TiO2/Ag/TiO2 for solar energy collection and radiation insulation
Authors: Fan John C. C. , Bachner Frank J. , Foley George H. , Zavracky Paul M.
Published: January 2004

Transparent heat-mirror films of TiO2/Ag/TiO2 on glass with a visible transmission of 84% (at 0.5 μm) and an infrared reflectivity of 98–99% (at 10 μm) have been fabricated by rf sputtering. Initial tests indicate that the films are thermally stable in air at 200°C and inert to water attack. Because of their excellent optical properties and apparent stability, these transparent heat-mirror films offer great promise for use in solar-thermal power conversion and as transparent thermal insulators.
Analysis of carrier collection efficiencies of thin-film silicon solar cells
Authors: Escher J. S. , Redfield D.
Published: January 2004

Carrier collection efficiencies in a silicon p -n junction solar cell are calculated as a function of base thickness for a range of 0.1–100 μm. Using the most realistic values of carrier diffusion lengths and surface recombination velocities, it is shown that thin-film silicon cells can yield unexpectedly good efficiencies.
Influence of device fabrication parameters on gradual degradation of (AlGa)As cw laser diodes
Authors: Ladany I. , Kressel H.
Published: January 2004

Several factors not previously associated with cw laser degradation are shown to influence the life and reliability of (AlGa)As cw injection laser diodes. They include zinc diffusion, sawing damage, and facet erosion. When proper attention is paid to these factors, lasers showing no significant degradation for at least 2000 h can be made.
Borosilicate clad fused silica core fiber optical waveguide with low transmission loss prepared by a high-efficiency process
Authors: Dabby F. W. , Pinnow D. A. , Ostermayer F. W. , Van Uitert L. G. , Saifi M. A. , Camlibel I.
Published: January 2004

A method for making fused silica core-borosilicate clad optical fiber waveguides is described. The process involves the growth of a needlelike layer of borosilicate glass onto the surface of a commercially available high-purity fused silica rod by an efficient flame reaction of boron and silicon hydrides with oxygen. The needlelike layer is subsequently heat treated at relatively low temperature to form a homogeneous bubble-free glass with a smooth surface. It is then covered with a thin protective jacket of silica and drawn into a fiber. These fibers have attenuation coefficients only slightly greater than the bulk loss of the fused silica core materials. Over the Al1−xGaxAs injection laser wavelength range, 0.82–0.88 μm, the loss is 5 dB/km, while at the YAG : Nd laser wavelength, 1.06 μm, it is 3 dB/km. The process appears to be attractive for the economical manufacture of low-loss fibers due to its simplicity and high chemical conversion efficiency.
Control of optical damage in reduced LiNbO3 by external applied field
Authors: Ohmori Y. , Yasojima Y. , Inuishi Y.
Published: January 2004

The correlation between the susceptibility of refractive index damage (optical damage) and photoconductivity, and the effect of external applied field have been studied in reduced LiNbO3. The magnitude of the photocurrent is proportional to the refractive index changes. The photocurrent and the optical damage vary with the external applied field depending upon the value of the built-in internal field. The values of the built-in field which causes optical damage have been estimated from the extrapolation of the photocurrent and the refractive index change versus the external applied field curves. It turns out that optical damage in reduced LiNbO3 can be easily controlled by applying an external field.
New observations on near band-edge luminescence in gallium arsenide phosphide (GaAs1−xPx)
Authors: Roessler David M. , Wu Tao-Yuan
Published: January 2004

We have found that the photoluminescence peak energy of n-type GaAs1−xPx crystals in the range 0.3<x<0.5 is exceptionally sensitive to the carrier concentration even in lightly doped material (< 1017 carriers cm−3). For all the crystals examined, the room-temperature photoluminescence spectrum consists of a single band corresponding to near band-edge emission. In crystals containing less than 1016 carriers cm−3, the peak energy variation with crystal composition lies close to a straight line connecting the direct band gaps of GaAs and GaP. In crystals deliberately doped with sulfur or selenium to concentrations in the 1016–1018-cm−3 range, the variation is close to the quadratic expression for band-gap variation with a bowing parameter of c =0.21.
Value of electron diffusion constant in GaAs for high electric field
Authors: Castelain André , Perichon Robert , Constant Eugène , Le Borgne Alain
Published: January 2004

The value of the electron diffusion constant in GaAs for electric fields of nearly 50 and 150 kV/cm has been estimated by measuring microwave impedances of two double-step doping profile (``high-low'') GaAs IMPATT diodes. In the investigated cases, it is shown that the electron diffusion constant does not exceed 20 and 50 cm2/s for E =50 and 150 kV/cm, respectively.
Photochemical products in coumarin laser dyes
Authors: Winters B. H. , Mandelberg H. I. , Mohr W. B.
Published: January 2004

The photochemical degradation processes occurring in a flashlamp-pumped dye laser using an ethanol solution of 7-diethylamino-4-methylcoumarin have been investigated in detail. The pump radiation gives rise to two irreversible reaction paths, resulting in a total of five photochemical products. One of these substances inhibits laser action because of its optical absorptivity at laser wavelengths. Suggestions for extending dye lifetimes based on this investigation are given.
Liquid phase epitaxial In1−x Gax P1−z Asz/GaAs1−y Py quaternary (LPE)-ternary (VPE) heterojunction lasers (x ∼0.70, z ∼0.01, y ∼0.40; λ < 6300 Å, 77°K)
Authors: Coleman J. J. , Hitchens W. R. , Holonyak N. , Ludowise M. J. , Groves W. O. , Keune D. L.
Published: January 2004

Laser operation (77°K) of LPE In1−x Gax P1−zAsz/ GaAs1−yPy (x ∼0.70, y ∼0.40, z ∼0.01) heterojunctions is demonstrated at λ<6300 Å. The junctions are prepared by the LPE growth of laser-quality p-type In1−x Gax P1−zAsz layers on n-type VPE GaAs1−yPy substrates. It is found that the problem of lattice matching In1−xGaxP on a GaAs1−yPy substrate is eased if the ternary is rendered a quaternary by the incorporation of a small amount of As in the LPE layer. During growth of the resulting p-type quaternary layer, Zn diffuses into the n-type ternary substrate, yielding a thin compensated active region. Laser operation of these devices is obtained at significantly shorter wavelengths and lower thresholds than for comparable homojunctions.
Direct interferometric measurements of the nonlinear refractive index coefficient n2 in laser materials
Authors: Bliss E. S. , Speck D. R. , Simmons W. W.
Published: January 2004

To properly account for nonlinear propagation effects in the design of a large laser system, it is necessary to know the nonlinear refractive index coefficient n2 of each system component. We report values of n2 for YAG, ED-2 laser glass, EY-1 Faraday rotator glass, and FR-4 rotator glass. The measurements were made at 1.06 μm using a time-resolved Mach-Zehnder interferometer to directly observe the variation of refractive index with intensity during the transmission of pulses 150 psec in duration.
Laser oscillation on the green bands of XeO and KrO
Authors: Powell H. T. , Murray J. R. , Rhodes C. K.
Published: January 2004

Laser oscillation has been observed on the green bands of the XeO and KrO excimers using direct electron beam excitation of high-pressure Xe or Kr containing small concentrations of O2. These bands are transitions between molecular levels correlating to the 1S0 and 1D2 metastable levels of atomic oxygen plus ground-state Xe or Kr. The XeO laser emission is at a number of wavelengths between 5300 and 5550 Å, while the KrO emission is at a single wavelength near the free atom line at 5577 Å. Laser pulse energies of 10 mJ and peak powers of 100 kW are seen for both excimers.
The blast probe: An inexpensive laser-blast wave energy monitor
Authors: Mayer Frederick J.
Published: January 2004

A simple-to-build and inexpensive Langmuir-probe-type device for determining the time of arrival of a laser-produced blast wave is described. Construction details, typical results, and the method of extracting the blast wave energy are presented. The blast wave energy is shown to be easily determined from the nondimensional form of the blast wave R/t versus R curve.
Superfluorescent laser emission from electron-beam-pumped Ar–N2 mixtures
Authors: Searles S. K.
Published: January 2004

Intense superfluorescent laser pulses on the nitrogen second positive transition N2(C)-N2(B) at 357.7 nm were generated by electron beam excitation of Ar–N2 mixtures at pressures from 600 to 5000 Torr. The pressure range over which the laser operated is explained on the basis of a simple kinetic model. The efficiency of the laser is discussed in detail.
Intracavity millimeter-wave coupling modulation of a CO2 laser
Authors: Bonek Ernst , Korecky Herbert
Published: January 2004

Intracavity modulation of a CO2 laser with 54 GHz in a scheme combining coupling modulation and a standing-wave modulator is reported. Utilizing the transverse electro-optic effect in semi-insulating GaAs, either the P(18) or the P(20) laser line of the 10.6-μm band was modulated to yield at least 0.1 mW for 1-W drive power in each sideband.
Minority carrier lifetime in InAs epilayers
Authors: Wieder H. H. , Collins D. A.
Published: January 2004

The effective minority carrier lifetime in extrinsic ∼17-μm-thick n -type InAs epilayers with 1.1×1015/cm3 donor impurities, grown by chemical vapor phase procedures on semi-insulating GaAs, was determined to be τe(77°K)=3.18 μsec. It is assumed that the lifetime of carriers is limited by bulk Auger recombination and by surface recombination. The calculated surface lifetime, τS=3.19 μsec, dominates the bulk Auger recombination lifetime, τA=7.67×10−4 sec in VPE layers. In liquid phase homoepitaxially grown InAs epilayers of comparable thickness with donor impurities Nd=2.9×1016/cm3 the calculated 77°K effective lifetime is τe=0.87 μsec; it is the reciprocal of the sum of the reciprocals of τS and of the calculated τA(77°K)=1.2 μsec, in good agreement with the measured τe=0.85 μsec.
A two-phase germanium charge-coupled device
Authors: Schroder D. K.
Published: January 2004

A germanium charge-coupled device has been fabricated and successfully operated. It consists of a ten-stage two-phase device in which directionality is achieved by a two-level oxide with self-aligned angle-evaporated aluminum electrodes. The device has been operated over the temperature range of 100–265°K at clock frequencies of 10–300 kHz. Transfer efficiencies of 95 and 97.5% without background charge and with 20% charge, respectively, have been measured.