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19 Oct 1998

Volume 73, Issue 16, pp. 2233-2380

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Analysis of terahertz pulse measurement with a chirped probe beam

F. G. Sun, Zhiping Jiang, and X.-C. Zhang

Appl. Phys. Lett. 73, 2233 (1998); http://dx.doi.org/10.1063/1.121685 (3 pages) | Cited 27 times

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In this letter, terahertz (THz) pulse measurements with a chirped probe pulse are analyzed. The method of stationary phase is used to explore the relation between the temporal waveform of an input THz pulse and spectral distribution of an output probe pulse on a detector array. The dependence of the temporal resolution on the chirp rate, the spectrum of the chirped probe beam, and the spectral resolution of the spectrometer is discussed. We confirm that the temporal resolution of the chirped pulse technique is equal to the square root of the product of the original unchirped probe pulse duration and the chirped pulse duration. © 1998 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Pw Imaging detectors and sensors

Directionally sensitive photorefractive interferometric line receiver for ultrasound detection on rough surfaces

Hemmo Tuovinen and Sridhar Krishnaswamy

Appl. Phys. Lett. 73, 2236 (1998); http://dx.doi.org/10.1063/1.121687 (3 pages) | Cited 4 times

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An adaptive heterodyne interferometer is configured as a line receiver using wave mixing in photorefractive bismuth silicate crystal. The line receiver is directionally most sensitive to ultrasound impinging normal to the line, and is significantly less sensitive to ultrasound impinging in other directions. Such a system is attractive in situations where the ultrasonic scatter from a specific direction is to be selectively pulled out in the presence of scatter from other “noise” sources. It is also demonstrated that the line probe system can be used to bridge the sensitivity gap that optical detection thus far has suffered vis-à-vis piezoelectric detection. © 1998 American Institute of Physics.
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07.60.Ly Interferometers
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Gi Light-sensitive materials
42.79.Jq Acousto-optical devices
43.38.Zp Acoustooptic and photoacoustic transducers
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing

Pinning of daisy modes in optically pumped vertical-cavity surface-emitting lasers

S. F. Pereira, M. B. Willemsen, M. P. van Exter, and J. P. Woerdman

Appl. Phys. Lett. 73, 2239 (1998); http://dx.doi.org/10.1063/1.121688 (3 pages) | Cited 9 times

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We have observed stable single-mode oscillation of optically pumped vertical-cavity surface-emitting lasers (i.e., without fabricated aperture) in several high-order daisy modes. The surprising stability of the nodal lines of a daisy mode is explained as being due to the combined action of many microscopic defects; when a daisy mode is moved across the wafer, the effective correlation length of the orientation of the pinning is of the order of 1 μm. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Laser action in GaN pyramids grown on (111) silicon by selective lateral overgrowth

S. Bidnyk, B. D. Little, Y. H. Cho, J. Krasinski, J. J. Song, W. Yang, and S. A. McPherson

Appl. Phys. Lett. 73, 2242 (1998); http://dx.doi.org/10.1063/1.121689 (3 pages) | Cited 33 times

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Laser action was observed in GaN pyramids under strong optical pumping at room temperature. The pyramids were laterally overgrown on a patterned GaN/AlN seeding layer grown on a (111) silicon substrate by metal–organic chemical vapor deposition. Each pyramid had a 15-μm-wide hexagonal base and was on average 15 μm in height. The pyramids were individually pumped, imaged, and spectrally analyzed through a high-magnification telescope system using a high-density pulsed excitation source. Under high levels of optical pumping, multimode laser at room temperature was observed. The integrated emission intensity for both spontaneous and lasing peaks was studied as a function of excitation power density. The effects of pyramid geometry and short-pulse excitation on the multimode nature of laser oscillations inside of the pyramids is discussed. This study suggests that GaN microstructures could potentially be used as pixel elements and high-density two-dimensional laser arrays. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Linear and nonlinear optical properties of stepped InxGa1−xAs/GaAs quantum wells

N. Tomassini, A. D’Andrea, M. Righini, S. Selci, L. Calcagnile, R. Cingolani, D. Schiumarini, and M. G. Simeone

Appl. Phys. Lett. 73, 2245 (1998); http://dx.doi.org/10.1063/1.121690 (3 pages) | Cited 2 times

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Systematic studies of polaritons in single stepped quantum wells are performed, and the presence of forbidden transitions in optical spectra are taken as a fingerprint of nonhomogeneous indium concentration. The large intensities of such transitions for well thicknesses in the range of quasi-two-dimensional exciton behavior are pointed out. Finally, second harmonic generation excited at half gap is found to be enhanced with respect to the bulk contribution as suggested by the theory. © 1998 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Dielectric properties of epitaxial BaTiO3 thin films

B. H. Hoerman, G. M. Ford, L. D. Kaufmann, and B. W. Wessels

Appl. Phys. Lett. 73, 2248 (1998); http://dx.doi.org/10.1063/1.121691 (3 pages) | Cited 32 times

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The dielectric response of epitaxial BaTiO3 thin films deposited on MgO was measured through surface electrodes as a function of applied bias, frequency, and temperature. The room temperature value of the dielectric constant was ∼500 with a dissipation factor, tan(δ), of 0.05 at 100 kHz. Measurements varying the bias field showed hysteresis of the dielectric response and a tunability of 30% for a maximum applied field of ∼7 MV/m. The frequency response of the dielectric constant is well described by a Curie–von Schweidler power law with an exponent ∼0.04 in the range 1 kHz–13 MHz. The films undergo a diffuse phase transition at temperatures higher than the bulk Curie temperature. The behavior of the dielectric response is attributed to the presence of residual strain in the epitaxial thin films. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point
77.55.-g Dielectric thin films

ZnSTe-based Schottky barrier ultraviolet detectors with nanosecond response time

Z. H. Ma, I. K. Sou, K. S. Wong, Z. Yang, and G. K. L. Wong

Appl. Phys. Lett. 73, 2251 (1998); http://dx.doi.org/10.1063/1.121692 (3 pages) | Cited 13 times

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ZnSTe-based Schottky barrier photovoltaic detector arrays were fabricated on GaP(100) using a two-step molecular beam epitaxy growth approach. These detectors exhibit visible blind and ultraviolet (UV) sensitive response with a peak UV responsivity of 0.13 A/W and 1.2×106 V/W at 320 nm. The built-in potential of these detectors was determined to be 1.7 V. The temporal photocurrent response of a 400×400 μm2 detector was measured to be 1.2 ns, limited apparently by the resistance-capacitance (rc) constant of the detector structure. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Emission process in bilayer organic light emitting diodes

C. Hochfilzer, G. Leising, Y. Gao, E. Forsythe, and C. W. Tang

Appl. Phys. Lett. 73, 2254 (1998); http://dx.doi.org/10.1063/1.121693 (3 pages) | Cited 8 times

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Efficient organic light emitting devices (OLEDs) using methyl substituted ladder-type poly (paraphenylene) (m-LPPP) and tris(8-hydroxy) quinoline aluminum (Alq3) as active materials are presented. For bilayer OLEDs the emissive region is found to be in both layers adjacent to the m-LPPP/Alq3 interface. The performance of these hybrid devices with constant m-LPPP thickness and varying Alq3 thickness is compared to that of a single layer m-LPPP device by investigating the relative spatial distribution of the light emission. The relation between the intensity of the light emitted from each layer and the distance to the cathode metal is discussed. Furthermore, the m-LPPP emission is also affected by the internal electric field at the interface. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices

Intracavity white-light continuum generation in a femtosecond Ti:sapphire oscillator

J.-P. Likforman, A. Alexandrou, and M. Joffre

Appl. Phys. Lett. 73, 2257 (1998); http://dx.doi.org/10.1063/1.121694 (3 pages) | Cited 1 time

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We report on intracavity white-light continuum generation in a Ti:sapphire oscillator at an average repetition rate of 200 kHz. A spectrally resolved pump-probe experiment is performed in order to demonstrate the potentialities of these continuum femtosecond pulses. © 1998 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.47.-p Spectroscopy of solid state dynamics
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Near-field scanning photoluminescence measurements using an uncoated fiber tip: A potential high resolution diagnostic technique for semiconductor devices

Ki-Bong Song, Ji-Eun Bae, Kyuman Cho, Sang-Youp Yim, and Seung-Han Park

Appl. Phys. Lett. 73, 2260 (1998); http://dx.doi.org/10.1063/1.121695 (3 pages) | Cited 5 times

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Near-field scanning optical microscopy, in which an uncoated fiber tip is used for delivering excitation light and picking up photoluminescence, is applied for diagnosing defects in semiconductor devices. Using this high resolution, potentially subdiffraction limited, and fast acquisition time scanning μ-photoluminescence (PL) technique, we are able to locate nonluminescing defects in a multiple quantum well grown by molecular beam epitaxy. Near-field characteristics of the measured spectral PL intensity are also discussed. © 1998 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.60.Vg Fiber-optic instruments
07.60.Pb Conventional optical microscopes
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors
61.72.-y Defects and impurities in crystals; microstructure
78.55.Cr III-V semiconductors

Strain compensated In1−xGaxAs(x<0.47) quantum well photodiodes for extended wavelength operation

J. Christopher Dries, Milind R. Gokhale, K. John Thomson, Stephen R. Forrest, and Robert Hull

Appl. Phys. Lett. 73, 2263 (1998); http://dx.doi.org/10.1063/1.121696 (3 pages) | Cited 12 times

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The use of highly strained (−2.0%) In0.83Ga0.17As quantum wells for the detection of light to a wavelength of λ∼2.0 μm is reported. Crystal quality for a 50 period multiple quantum well (MQW) detector grown on InP substrates is maintained through strain compensation using tensile strained In0.83Ga0.17P barriers. Transmission electron microscopy and double crystal x-ray diffraction reveal smooth interfaces and no observable defects for In0.83Ga0.17As layers with widths less than 80 Å. Single-pass quantum efficiencies of 30% have been achieved at λ=1.95 μm, using a 75 μm diam MQW, strain-compensated, top illuminated, low dark current (∼250 pA at 20 V) p-i-n detector. The theoretical cutoff wavelength limit for diodes fabricated using this technique is calculated to be λ=2.15 μm. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Surface-emitting, distributed-feedback diode lasers with uniform near-field intensity profile

James Lopez, Masoud Kasraian, and Dan Botez

Appl. Phys. Lett. 73, 2266 (1998); http://dx.doi.org/10.1063/1.121697 (3 pages) | Cited 2 times

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Theoretical analysis of second-order surface-emitting, complex-coupled distributed feedback diode lasers with first-order distributed Bragg reflectors (DBR) is presented. The DBR reflectors are shown to insure simultaneous operation in a virtually uniform near-field profile with high efficiency and adequate intermodal discrimination. Such devices display symmetric-mode (single-lobe) surface emission with relatively high external differential quantum efficiency (30%), low gain threshold (18 cm−1), and <8% near-field intensity profile variations (in the longitudinal direction). The devices have the potential to provide >100 mW of stable, single-mode cw power, significantly higher than it is possible with vertical-cavity surface-emitting lasers. It is also shown that the device studied here can be combined with a resonant optical waveguide array device to produce a 2D uniform near-field surface-emitting source capable of providing greater than 1 W cw power in a stable, single-lobed beam. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Intensity and polarization switching behaviors of light emission induced with a scanning tunneling microscope

Zhanghua Wu, Tomonobu Nakayama, Shan Qiao, and Masakazu Aono

Appl. Phys. Lett. 73, 2269 (1998); http://dx.doi.org/10.1063/1.121698 (3 pages) | Cited 1 time

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By applying voltage pulses across the tunnel junction, switching behaviors of the intensity and the polarization of light emission induced with a scanning tunneling microscope (STM) are observed. The STM images taken subsequently indicate that these switching behaviors are caused by a cluster with asymmetric shape on the nanometer scale being transferred between the sample and the tip by the pulse applied. Possible mechanisms for the switching behaviors are discussed. These observations could find applications in photonic devices on the nanometer scale. © 1998 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
78.60.Fi Electroluminescence
42.25.Ja Polarization
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Room-temperature formation of erbium-related luminescent centers in anodic alumina

S. K. Lazarouk, A. V. Mudryi, and V. E. Borisenko

Appl. Phys. Lett. 73, 2272 (1998); http://dx.doi.org/10.1063/1.121699 (3 pages) | Cited 12 times

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Luminescent Er-doped Al2O3 films have been fabricated at room temperature by a technique including magnetron deposition of Er-doped Al film on a silicon substrate and its subsequent electrochemical anodization. The films demonstrate strong Er-related photoluminescence at about 1.53 μm as recorded in the temperature range of 4.2–300 K. The effect is not influenced by annealing of the samples up to 200 °C. Upon annealing at 300–500 °C the luminescence intensity decreases, while above 600 °C it starts to recover. Annealing at 1000 °C restores the photoluminescence spectra to the initial level. The annealing peculiarities observed have been explained by dominant hydrogen outdiffusion at 300–500 °C, rearrangement of point defects at 600–800 °C, and recrystallization processes above 850 °C in the alumina film. Activation energies of these processes have been estimated to be 0.76 eV (for parabolic rate), 0.58 eV (for linear rate), and 0.46 eV (for linear rate), respectively. © 1998 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
71.55.Ht Other nonmetals
61.72.Cc Kinetics of defect formation and annealing
82.45.-h Electrochemistry and electrophoresis

Raman imaging of patterned silicon using a solid immersion lens

C. D. Poweleit, A. Gunther, S. Goodnick, and José Menéndez

Appl. Phys. Lett. 73, 2275 (1998); http://dx.doi.org/10.1063/1.121700 (3 pages) | Cited 21 times

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We show an enhanced spatial resolution using a solid immersion lens by directly imaging the Raman scattered light from silicon masked by periodic metal lines. A glass hemisphere solid immersion lens with an index of refraction n = 1.868 at 488 nm is used in conjunction with a 100×0.8 numerical aperture objective to obtain the enhanced spatial resolution. The increased numerical aperture is demonstrated by a direct line scan over the periodic metal lines. Compared with near-field optical microscopy, the solid immersion lens technique overcomes the difficulty of limited excitation power obtainable with tapered fibers, while providing excellent spatial resolution which in principle could be extended to the 0.1 μm range. © 1998 American Institute of Physics.
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78.30.Am Elemental semiconductors and insulators
07.60.Rd Visible and ultraviolet spectrometers
42.79.Bh Lenses, prisms and mirrors
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
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