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27 Oct 2003

Volume 83, Issue 17, pp. 3447-3628

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 3453 (2003); http://dx.doi.org/10.1063/1.1622431 (3 pages)

Giacomo Scalari, Stéphane Blaser, Lassaad Ajili, Jérôme Faist, Harvey Beere, Edmund Linfield, David Ritchie, and Giles Davies
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Fundamental mode 5 GHz surface-acoustic-wave filters using optical lithography

T. Makkonen, V. P. Plessky, W. Steichen, S. Chamaly, C. Poirel, M. Solal, and M. M. Salomaa

Appl. Phys. Lett. 83, 3596 (2003); http://dx.doi.org/10.1063/1.1618366 (3 pages) | Cited 1 time

Online Publication Date: 20 October 2003

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Resonators and bandpass filters have been implemented in the 5 GHz frequency range, based on “longitudinal leaky” surface-acoustic waves on standard YZ-cut lithium niobate substrate. The synchronous one-port resonators constituting a ladder filter operate in the fundamental mode. The electrode width in the resonators is above 0.25 μm, thus making them readily accessible for fabrication with optical lithography. Test resonators are fabricated to study the effects of the metallization ratio and aperture on the resonator behavior. For the prototype filter, a center frequency of 5.20 GHz, a wide fractional 3 dB bandwidth of 6.3%, a minimum insertion loss of 3.3 dB and a high stopband suppression of 25 dB have been achieved. © 2003 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Polymer thin films containing Eu(III) complex as lanthanide lasing medium

Yasuchika Hasegawa, Yuji Wada, Shozo Yanagida, Hideki Kawai, Naoki Yasuda, and Toshihiko Nagamura

Appl. Phys. Lett. 83, 3599 (2003); http://dx.doi.org/10.1063/1.1616207 (3 pages) | Cited 25 times

Online Publication Date: 20 October 2003

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Direct evidence of lanthanide(III) lasing using Eu(III) complex in polymer thin films (threshold level <0.05 mJ) is reported. The thin film consists of polystyrene containing Eu(III) complexes based on two criteria: (1) Higher emission quantum yield of Eu(III) complexes, which increases the rs (energy density), and (2) faster radiation rate at large B (Einstein coefficient). The microcavity was constructed by coating a glass substrate with a film having a high refractive index. The film thickness was found to be 1.71 mm. The threshold level for laser transmission was found to be <0.05 mJ. © 2003 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
42.55.Sa Microcavity and microdisk lasers

High-resolution bistable nematic liquid crystal device realized on orientational surface patterns

Jong-Hyun Kim, Makoto Yoneya, and Hiroshi Yokoyama

Appl. Phys. Lett. 83, 3602 (2003); http://dx.doi.org/10.1063/1.1623011 (3 pages) | Cited 8 times

Online Publication Date: 20 October 2003

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The four-fold symmetry of a checkerboard-like surface alignment consisted of square domains arrived at the macroscopic orientational bistability of nematic liquid crystals. Switching between the two orientations took place with an appropriate electric field. Here the threshold field of bistable switching decreased as temperature increased, and the light could heat only the selected region in the cell including a light-absorbing medium. Irradiating the laser concurrently with an electric field, we addressed a selected region in the alignment pattern without the disturbance of neighboring regions. Extending this process, we realized an extremely fine bistable device of nematic liquid crystal with a pixel size down to about 2 μm. © 2003 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
64.70.M- Transitions in liquid crystals
42.70.Df Liquid crystals
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Pv Polymers, organic compounds

High-power operation of electroabsorption modulators

Zhixi Bian, James Christofferson, Ali Shakouri, and Peter Kozodoy

Appl. Phys. Lett. 83, 3605 (2003); http://dx.doi.org/10.1063/1.1623338 (3 pages) | Cited 3 times

Online Publication Date: 20 October 2003

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Using a thermoreflectance imaging technique, surface temperature of active electroabsorption modulators is measured at different incident powers and modulator biases. Excellent agreement is obtained between these data and the results of a self-consistent finite element model. It is shown experimentally and theoretically that thermal runaway at high-power operation can be avoided by improving the thermal design of the device. High-power operation is achieved in an optimized device structure, yielding a high, damage-free power dissipation level in excess of 300 mW. © 2003 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
02.70.Dh Finite-element and Galerkin methods

Improvement of near-ultraviolet InGaN/GaN light-emitting diodes by inserting an in situ rough SiNx interlayer in n-GaN layers

Ru-Chin Tu, Chang-Cheng Chuo, Shyi-Ming Pan, Yu-Mei Fan, Ching-En Tsai, Te-Chung Wang, Chun-Ju Tun, Gou-Chung Chi, Bing-Chi Lee, and Chien-Ping Lee

Appl. Phys. Lett. 83, 3608 (2003); http://dx.doi.org/10.1063/1.1622441 (3 pages) | Cited 12 times

Online Publication Date: 20 October 2003

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Near-ultraviolet 400-nm InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with and without an in situ rough SiNx interlayer inserted into the n-GaN underlying layer were grown on c-face sapphire substrates by metalorganic vapor phase epitaxy. Inserting the SiNx interlayer into the n-GaN underlying layer slightly reduced leakage current induced by reducing the defect density. Additionally, an enhancement of light extraction for the LED with a SiNx interlayer is expected because of the increased intensity of light scattered on the SiNx nanomask, changing the directions of propagation of light. Consequently, the emission efficiency of an LED with an in situ rough SiNx interlayer doubles that without a SiNx interlayer. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Electric field screening in polymer light-emitting diodes

P. A. Lane, J. C. deMello, R. B. Fletcher, and M. Bernius

Appl. Phys. Lett. 83, 3611 (2003); http://dx.doi.org/10.1063/1.1623014 (3 pages) | Cited 24 times

Online Publication Date: 20 October 2003

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Electromodulation (EM) spectroscopy has been used to probe the electric field distribution in polymer light-emitting diodes. Below the turn-on bias, the EM spectrum is dominated by electroabsorption of the emissive layer. The electroabsorption signal vanishes above the turn-on bias. Under operation, the EM spectrum is composed of bleaching of the emissive layer absorption and excited state absorption from trapped charge with no trace of the electroabsorption signal remaining. We conclude that the internal electric field is effectively screened by accumulation of trapped electrons at the anode. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.66.Qn Polymers; organic compounds
78.20.Jq Electro-optical effects
42.79.Hp Optical processors, correlators, and modulators
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption

Voltage-controlled spectral tuning of photoelectric signals in a conducting polymer-bacteriorhodopsin device

A. G. Manoj and K. S. Narayan

Appl. Phys. Lett. 83, 3614 (2003); http://dx.doi.org/10.1063/1.1623007 (3 pages) | Cited 5 times

Online Publication Date: 20 October 2003

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Bacteriorhodopsin (bR), a protein existing in the halobacterial purple membrane serves as a light-driven pump which sets up an electrochemical gradient and transports protons across the cell membrane. In this report, we explore the synergetic processes at a conducting polymer/bR interface due to photoexcitation in presence of a voltage bias. The possibility of changing the oxidation state of the polymer electrochemically is coupled to the optically activated proton gradient in the bR side. This approach of controlling the nature of the conducting polymer-bR interface demonstrates a facile route to stabilize the deprotonated, long-lived intermediate state present in the bR photocycle. These processes result in interesting solid-state device properties such as incident-wavelength-controlled rectification of the photoinduced current and voltage-controlled spectral responses. © 2003 American Institute of Physics.
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85.65.+h Molecular electronic devices
87.14.E- Proteins
87.15.B- Structure of biomolecules
72.40.+w Photoconduction and photovoltaic effects
72.15.Nj Collective modes (e.g., in one-dimensional conductors)

Highly sensitive ultraviolet detector based on ZnO/LiNbO3 hybrid surface acoustic wave filter

Parmanand Sharma and K. Sreenivas

Appl. Phys. Lett. 83, 3617 (2003); http://dx.doi.org/10.1063/1.1622436 (3 pages) | Cited 30 times

Online Publication Date: 20 October 2003

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Fabrication of a highly-sensitive UV detector based on the surface-acoustic-wave (SAW) principle is reported. The output voltage of the SAW oscillator constructed with a ZnO/LiNbO3 hybrid SAW filter was found to decrease linearly with increasing UV light intensity, and a very low intensity UV light of 10 μW/cm2 was detected easily. Our results show its potential use in wireless UV measurement systems. © 2003 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
43.60.Vx Acoustic sensing and acquisition
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