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25 Dec 1989

Volume 55, Issue 26, pp. 2689-2791

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Sealed cw transversely excited CO2 laser operated with active catalysts

Kaung‐Hsiung Wu

Appl. Phys. Lett. 55, 2689 (1989); http://dx.doi.org/10.1063/1.101968 (3 pages) | Cited 2 times

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Two catalysts having the forms of tin‐oxide‐coated metal surfaces and platinum, palladium, and rhodium supported on cordierite (2MgO⋅2Al2O3⋅5SiO2) have been introduced for the first time in a cw transversely excited (TE) CO2 laser to perform a long‐term sealed‐off operation. Temporal variations of gas compositions and discharge conditions with and without these catalysts are analyzed. Sealed‐off operation with an output level at 550 W for more than 110 h of discharge time was achieved.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
78.60.Ps Chemiluminescence

Extremely high damage threshold of a new nonlinear crystal L‐arginine phosphate and its deuterium compound

Atsushi Yokotani, Takatomo Sasaki, Kunio Yoshida, and Sadao Nakai

Appl. Phys. Lett. 55, 2692 (1989); http://dx.doi.org/10.1063/1.101969 (2 pages) | Cited 47 times

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L‐arginine phosphate monohydrate (LAP) and deuterated LAP (DLAP) are new organic nonlinear optical materials useful for higher harmonics of radiation from high‐power lasers. We measured the bulk laser damage threshold of these crystals using light from a 1.05 μm laser with 1 and 25 ns pulse widths and 0.53 μm laser light with 0.6 and 20 ns pulse widths. In every case, these crystals show much higher thresholds than potassium dihydrogen phosphate (KDP and fused silica. These crystals are very interesting not only as a frequency converter but also as other optical components of high‐power lasers, because of their extremely high damage threshold.
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42.70.-a Optical materials
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.55.Rz Doped-insulator lasers and other solid state lasers

Mode locking of high‐power neodymium:yttrium aluminum garnet lasers at ultrahigh repetition rates

Theodore Sizer

Appl. Phys. Lett. 55, 2694 (1989); http://dx.doi.org/10.1063/1.101970 (2 pages) | Cited 1 time

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A high‐power lamp‐pumped Nd:YAG laser has been harmonically mode locked using a specially fabricated GaP mode locker at repetition rates of 0.25, 0.5, and 1 GHz. At these ultrahigh mode‐locking frequencies the pulse duration is reduced as well. Stable 31 ps pulses have been produced with 4 W of average output power.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Px Semiconductor lasers; laser diodes

Adjustable four‐electrode electron mirror as an aberration corrector

Zhifeng Shao and Xiao Dong Wu

Appl. Phys. Lett. 55, 2696 (1989); http://dx.doi.org/10.1063/1.101945 (2 pages) | Cited 7 times

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A numerical analysis of a four‐electrode electrostatic mirror is presented. The results indicate that this mirror provides correct aberrations as a corrector for electron optical systems and unlike all other mirror configurations known to date, this new system shows for the first time that an adjustable mirror, both in magnitude of the aberration coefficients and in the ratio of CS/Cc, can indeed be found in a practical system.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
41.75.Fr Electron and positron beams

Lasing threshold in quantum well surface‐emitting lasers: Many‐body effects and temperature dependence

P. L. Gourley, S. K. Lyo, T. M. Brennan, B. E. Hammons, C. F. Schaus, and S. Sun

Appl. Phys. Lett. 55, 2698 (1989); http://dx.doi.org/10.1063/1.101928 (3 pages) | Cited 13 times

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The geometry of quantum well surface‐emitting lasers has several important consequences. The ultrashort (∼1 μm) vertical cavity defines longitudinal modes with energy separation greater than the bandwidth of spectral gain. The optical confinement of these modes can approach unity. To achieve lasing, high carrier densities (∼1012 cm−2) in the quantum well are required. The confined carriers interact through enhanced many‐body exchange which influences both the lasing wavelength and threshold characteristics. Indeed, the exchange interaction can facilitate the lasing process. We theoretically and experimentally study the role of the short cavity and exchange interaction on the cw lasing threshold as a function of temperature. In constrast to edge emitters, the lasing threshold in these surface emitters exhibits a well‐defined minimum at a particular temperature. The temperature of the minimum can be designed by merely changing the active layer thickness.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Photorefractive characterization of deep level compensation in semi‐insulating GaAs

Afshin Partovi, Elsa M. Garmire, George C. Valley, and Marvin B. Klein

Appl. Phys. Lett. 55, 2701 (1989); http://dx.doi.org/10.1063/1.101929 (3 pages) | Cited 9 times

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We show that photorefractive beam coupling can be used for deep level spectroscopy in semi‐insulating GaAs. In four samples cut from different locations in a single boule of GaAs, we find the same degree of compensation as determined from absorption spectra, Hall measurements, and the photorefractive effect. In the most compensated of our samples, the sign of the photorefractive beam coupling changes from electron to hole dominated as the optical wavelength is changed from 1.06 to 1.15 μm. Furthermore, we show that absorption spectra for semi‐insulating GaAs can be used to choose samples for optimal photorefractive behavior at wavelengths of 0.9–1.5 μm.
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71.55.Eq III-V semiconductors
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
78.20.Jq Electro-optical effects
72.20.-i Conductivity phenomena in semiconductors and insulators

Optically pumped laser oscillation at ≊2.9 μm of a HgCdTe layer grown by metalorganic chemical vapor deposition

A. Ravid, A. Zussman, G. Cinader, and A. Oron

Appl. Phys. Lett. 55, 2704 (1989); http://dx.doi.org/10.1063/1.101930 (3 pages) | Cited 12 times

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Photopumped pulsed stimulated emission at 2.9 μm in a HgCdTe layer grown by metalorganic chemical vapor deposition on a CdTe substrate was studied as a function of temperature. The threshold power of the HgCdTe laser (photoexcited by a GaAs diode laser) increased from 0.04 W at 12 K to 1.58 W at 150 K. Above 50 K, the temperature dependence of the threshold is exponential, yielding a T0 of 31 K. From the observed laser emission wavelength a Cd mole fraction of x=0.422 was determined. The far‐field angular full width at e−2 of peak intensity was 5.5° and 9.5° perpendicular and parallel to the film plane, respectively.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.45.+h Stimulated emission
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

New emission spectra from oxygen

S. Yoshida, T. Tokuda, and K. Shimizu

Appl. Phys. Lett. 55, 2707 (1989); http://dx.doi.org/10.1063/1.101931 (2 pages) | Cited 11 times

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New emission spectra have been observed from chemically produced excited oxygen. Evidence that the observed visible emission is due to oxygen dimer transitions is presented. Experimental results suggest that the observed oxygen dimer is stable O4 molecule rather than the usually observed Van der Waals‐type dimolecular complex. The present system is discussed from the viewpoint of a new laser operating in the visible. The possibility of a similar oxygen‐dimer laser operating in the near infrared is also discussed.
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33.20.Kf Visible spectra
42.55.Ks Chemical lasers
42.55.Lt Gas lasers including excimer and metal-vapor lasers
78.60.Ps Chemiluminescence

Simplified scattering coefficient expressions for a spherical particle located on the propagation axis of a fifth‐order Gaussian beam

Scott A. Schaub, John P. Barton, and Dennis R. Alexander

Appl. Phys. Lett. 55, 2709 (1989); http://dx.doi.org/10.1063/1.101932 (3 pages) | Cited 15 times

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See Also: Erratum

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Expanding on developments presented in an earlier paper, theoretical expressions for the scattering coefficients of a homogeneous, absorbing, spherical particle irradiated by a fifth‐order Gaussian beam are presented for the special case of the particle center located on the propagation axis of the beam. For this case, evaluation of two‐dimensional surface integrals, required in computing the scattering coefficients for the most general particle location, is reduced to a computationally more efficient one‐dimensional integral. For a typical size parameter α=πd/λ=17, the CPU time required for calculation of scattering coefficients is reduced by a factor of ∼1500 by using the simplified coefficient expressions. In addition, computation of electromagnetic field components is reduced from double summation to single summation expressions, further simplifying the field calculations.
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42.25.Fx Diffraction and scattering
42.68.Mj Scattering, polarization

Impedance matching for enhanced waveguide/photodetector integration

R. J. Deri and O. Wada

Appl. Phys. Lett. 55, 2712 (1989); http://dx.doi.org/10.1063/1.101933 (3 pages) | Cited 15 times

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A novel impedance‐matched structure is proposed for improved coupling in evanescently coupled, integrated waveguide/photodetectors. We show that insertion of an impedance‐matching layer between waveguide and detector regions can improve the coupling by a factor of ≊7, resulting in shorter detectors with lower capacitance and higher frequency response. The impedance‐matching mechanism is discussed in detail.
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42.82.-m Integrated optics
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.-q Optoelectronic devices
42.79.Gn Optical waveguides and couplers

Single quantum wire semiconductor lasers

E. Kapon, S. Simhony, R. Bhat, and D. M. Hwang

Appl. Phys. Lett. 55, 2715 (1989); http://dx.doi.org/10.1063/1.101934 (3 pages) | Cited 65 times

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Single quantum wire GaAs/AlGaAs injection lasers were fabricated using organometallic chemical vapor deposition on V‐grooved GaAs substrates. The quantum wire active region has a crescent‐shaped cross section ∼100 Å thick and less than 1000 Å wide. Amplified spontaneous emission and lasing spectra of the quantum wire lasers exhibit effects due to transitions between quasi‐one‐dimensional subbands separated by ∼10 meV. Single quantum wire laser structures with tight optical confinement exhibited threshold currents as low as 3.5 mA for uncoated devices at room temperature.
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42.55.Px Semiconductor lasers; laser diodes
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Photorefractive effect in Ti‐diffused channel waveguides using LiNbO3 substrates with reduced optical absorption

Takumi Fujiwara, Akira Terashima, and Hiroshi Mori

Appl. Phys. Lett. 55, 2718 (1989); http://dx.doi.org/10.1063/1.102369 (3 pages) | Cited 10 times

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We report a remarkably reduced photorefractive sensitivity in Ti:LiNbO3 channel waveguides using substrates with reduced optical absorption near the absorption edge. In addition, the intensity dependence of the saturated index change was measured, which indicates that, based on the Glass model, the saturated value of photoinduced index change is independent of irradiation intensity in the high intensity limit.
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78.20.Jq Electro-optical effects
42.79.Gn Optical waveguides and couplers
42.82.-m Integrated optics
42.70.Gi Light-sensitive materials

Coherent, monolithic two‐dimensional strained InGaAs/AlGaAs quantum well laser arrays using grating surface emission

G. A. Evans, D. P. Bour, N. W. Carlson, J. M. Hammer, M. Lurie, J. K. Butler, S. L. Palfrey, R. Amantea, L. A. Carr, F. Z. Hawrylo, E. A. James, J. B. Kirk, S. K. Liew, and W. F. Reichert

Appl. Phys. Lett. 55, 2721 (1989); http://dx.doi.org/10.1063/1.102256 (3 pages) | Cited 14 times

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Two‐dimensional coherent strained‐layer InGaAs/AlGaAs quantum well laser arrays consisting of 100 (10×10) active elements have been fabricated and characterized. The central lobe of the far field has a full width at half power of 0.04°×1°. Observation of about 2 W peak power from either the substrate or the junction surface, with differential quantum efficiencies from each side of about 40%, is reported. The mode spectrum of the emitted power is contained in a ∼2 Å wavelength interval at ∼2 W.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Fabrication of microlasers and microresonator optical switches

A. Scherer, J. L. Jewell, Y. H. Lee, J. P. Harbison, and L. T. Florez

Appl. Phys. Lett. 55, 2724 (1989); http://dx.doi.org/10.1063/1.101935 (3 pages) | Cited 31 times

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We have microfabricated low‐threshold, high‐speed vertical‐cavity lasers and optical switches by optimizing the mirror design, crystal growth, and ion etching of microresonators. By minimizing the sidewall ion damage in electrically pumped microlasers, we have defined large arrays of 3‐μm‐diam surface‐emitting devices with threshold currents below 1.5 mA. Ion beam etching was also used to define 0.5–1.5 μm wide all‐optical microresonator switches with recovery times as low as 30 ps and controlling energies as low as 0.6 pJ.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Magnetosonic wave generation by super‐Alfvénic ion ring propagation in plasma

E. Schamiloglu, J. B. Greenly, and D. A. Hammer

Appl. Phys. Lett. 55, 2727 (1989); http://dx.doi.org/10.1063/1.101936 (3 pages) | Cited 3 times

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A weakly diamagnetic rotating proton beam propagating at about four times the Alfvén speed along a magnetized hydrogen plasma column generated magnetosonic waves when the beam rise time was less than about three radial Alfvén transit times. The waves were collisionally damped and the damping increased as the induced cross‐field plasma current became stronger. Our beam and plasma conditions suggest that the damping is due to an enhanced collision frequency resulting from a modified two‐stream instability.
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52.40.Mj Particle beam interactions in plasmas
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.55.Jd Magnetic mirrors, gas dynamic traps
52.50.Gj Plasma heating by particle beams

Conductance considerations in the reactive ion etching of high aspect ratio features

J. W. Coburn and Harold F. Winters

Appl. Phys. Lett. 55, 2730 (1989); http://dx.doi.org/10.1063/1.101937 (3 pages) | Cited 54 times

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Very simple vacuum conductance arguments indicate that in the reactive ion etching of high aspect ratio features, the conductance is adequate to allow etch products to flow out of the feature without building up a pressure which would allow gas phase collisions to become important. On the other hand, the conductance can be expected to limit the flow of the reactive species to the bottom of the feature where the etching is taking place, thus creating the possibility of an etch rate dependence on the aspect ratio of the etched feature.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Growth control of CdTe/CdZnTe (001) strained‐layer superlattices by reflection high‐energy electron diffraction oscillations

G. Lentz, A. Ponchet, N. Magnea, and H. Mariette

Appl. Phys. Lett. 55, 2733 (1989); http://dx.doi.org/10.1063/1.101938 (3 pages) | Cited 27 times

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We have used reflection high‐energy electron diffraction (RHEED) and x‐ray diffraction to study the growth of CdTe/Cd0.90 Zn0.10 Te (001) heterostructures by molecular beam epitaxy (MBE). A growth process involving an excess of Cd and growth interruptions at the well‐barrier interfaces has been found necessary to observe strong and persistent RHEED oscillations during the epitaxy of quantum wells and superlattices. This method gives accurate in situ thickness measurements of all the layers during the growth of CdTe/Cd0.90 Zn0.10 Te superlattices, in good agreement with x‐ray diffraction data. The sharpness of x‐ray diffraction satellites confirms the high crystalline quality of the superlattices with a period fluctuation of less than one monolayer.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation

Fine structure of the oxygen‐related local mode at 714 cm−1 in GaAs

H. Ch. Alt

Appl. Phys. Lett. 55, 2736 (1989); http://dx.doi.org/10.1063/1.102269 (3 pages) | Cited 32 times

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Infrared absorption measurements on a new third state of the Ga‐O‐Ga center in GaAs are reported. This state gives rise to a local mode at 714 cm−1, B′, which is shifted from the band B to lower energy by 0.67 cm−1. The B′ state acts as an intermediate state for the photoinduced conversion from the 730 cm−1 band, A, to B. The kinetics is quantitatively described by a model considering successive capture of conduction‐band electrons, which have been photoexcited from the EL2 level. The reappearance of the band A after quenching of EL2 occurs through the corresponding sequence B→B′→A. The experimental results favor the interpretation of B′ in terms of a third charge state being not accessible at thermal equilibrium conditions.
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71.55.Eq III-V semiconductors
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Low‐temperature diamond growth in a microwave discharge

W. L. Hsu, D. M. Tung, E. A. Fuchs, K. F. McCarty, A. Joshi, and R. Nimmagadda

Appl. Phys. Lett. 55, 2739 (1989); http://dx.doi.org/10.1063/1.101939 (3 pages) | Cited 17 times

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A new regime for plasma‐assisted chemical vapor deposition (CVD) of diamond is reported in which high quality diamond films can be deposited on silicon with relatively high ratios of methane in hydrogen mixtures and at significantly lower substrate temperatures than previously reported. The deposition was achieved in a microwave plasma discharge with a feed gas consisting of a mixture of only methane and hydrogen. The surface temperature of a molybdenum sample, when exposed to the same plasma environment, was measured at 500 °C with an infrared scanning camera. This substrate temperature is substantially lower than the 700–1000 °C range generally regarded as the optimal regime for CVD diamond growth. Analysis by Raman spectroscopy showed that films deposited with a 2% methane in hydrogen mixture produced a near graphite‐free diamond film at our reported low‐temperature regime, while deposition at 1000 °C resulted in films with a much higher graphitic content.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

New field‐effect resonant tunneling transistor: Observation of oscillatory transconductance

C. H. Yang, Y. C. Kao, and H. D. Shih

Appl. Phys. Lett. 55, 2742 (1989); http://dx.doi.org/10.1063/1.101940 (3 pages) | Cited 10 times

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We present device characteristics of a field‐effect, unipolar, resonant tunneling transistor. An oscillatory tunneling current in the transfer characteristics is observed for the first time. Our observation confirms a recent hypothesis that a mere three‐to‐two dimensional resonant tunneling can occur when scattering rate is less than the attempt frequency of tunneling electrons in the quantum well.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Tv Field effect devices
73.40.Gk Tunneling

Subgap absorption spectra of ion‐implanted Si and GaAs layers

L. Luciani, M. Marinelli, U. Zammit, R. Pizzoferrato, F. Scudieri, and S. Martellucci

Appl. Phys. Lett. 55, 2745 (1989); http://dx.doi.org/10.1063/1.101941 (3 pages) | Cited 10 times

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The subgap absorption spectra of ion‐implanted Si and GaAs layers are reported and the influence of increasing ion implantation dose is shown. The absorption spectra are shown to depend strongly on the implantation dose in the whole investigated spectrum before the layer amorphization dose is reached. Smaller changes are induced and only in a limited spectral region with further dose increases.
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78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
71.55.Jv Disordered structures; amorphous and glassy solids
81.40.Tv Optical and dielectric properties related to treatment conditions

Mechanism of subpicosecond electrical pulse generation by asymmetric excitation

E. Sano and T. Shibata

Appl. Phys. Lett. 55, 2748 (1989); http://dx.doi.org/10.1063/1.101942 (3 pages) | Cited 25 times

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Using full‐wave analysis, the motion of the electric field in a coplanar transmission line (two parallel lines) fabricated on nondamaged silicon‐on‐sapphire when a part of the gap between the two lines is excited by ultrashort optical pulse is demonstrated and the mechanism for the electrical pulse generation is discussed.
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84.40.Az Waveguides, transmission lines, striplines
84.30.Ng Oscillators, pulse generators, and function generators

Photoluminescence spectra of shallow acceptors in GaAs‐(Ga,Al)As quantum wells

L. E. Oliveira and J. López‐Gondar

Appl. Phys. Lett. 55, 2751 (1989); http://dx.doi.org/10.1063/1.101943 (3 pages) | Cited 8 times

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A theoretical study of the photoluminescence spectra associated with shallow acceptors in a GaAs‐(Ga,Al)As quantum well is performed. It is shown that an analysis of the acceptor‐photoluminescence line shape could allow an experimental determination of the quasi‐Fermi energy level of the conduction‐subband‐electron gas as well as of the on‐edge acceptor binding energy.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
78.55.Cr III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Outdiffusion of Cu through Au: Comparison of (100) and (111) Cu films epitaxially deposited on Si, and effects of annealing ambients

Chin‐An Chang

Appl. Phys. Lett. 55, 2754 (1989); http://dx.doi.org/10.1063/1.101944 (3 pages) | Cited 30 times

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Outdiffusion of Cu through thin gold films is studied as functions of Cu orientation and annealing ambients. (100) Cu films were epitaxially deposited on (100) Si, and (111) Cu on (111) Si, with commonly (111) oriented Au films deposited on Cu. Heating was conducted at 170 °C to minimize the Cu silicide formation. Structures with (111) Cu invariably give a higher surface accumulation of Cu than the counterparts of (100) Cu for each ambient, including the as‐deposited samples. The accumulation is the highest in air, followed by N2‐O2 and N2‐H2, in agreement with the ambient effects on many other systems with gold as the overcoating layer. The orientation dependence of the outdiffusion rates of Cu through Au is related to the bonding structures at the Au‐Cu interface. The face‐centered‐cubic structure of Cu makes the Au/Cu (111) interface more favorable for the release of Cu than the Au/Cu (100) interface, in agreement with the observed orientation dependence.
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66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)

New deep acceptor in epitaxial cubic SiC

J. A. Freitas and S. G. Bishop

Appl. Phys. Lett. 55, 2757 (1989); http://dx.doi.org/10.1063/1.101946 (3 pages) | Cited 9 times

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We have investigated the temperature and excitation intensity dependence of photoluminescence (PL) spectra in several undoped and lightly Al‐doped thin films of cubic SiC grown by chemical vapor deposition on Si substrates. The low‐power PL spectra in all samples studied exhibit a deep donor‐acceptor pair PL band which involves a previously undetected deep acceptor (EA=470 meV). The pervasive character of this deep acceptor suggests the possibility that it is at least partially responsible for the high compensation observed in undoped films of cubic SiC.
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78.55.Hx Other solid inorganic materials
78.66.-w Optical properties of specific thin films
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.55.-a Thin film structure and morphology
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