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22 Nov 1999

Volume 75, Issue 21, pp. 3243-3419

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Nanometer-Au-particle-enhanced photorefractivity in a polymer composite

Feng Wang, Zhijian Chen, Bo Zhang, Qihuang Gong, Kuiwang Wu, Xuesong Wang, Baowen Zhang, and Fangqiong Tang

Appl. Phys. Lett. 75, 3243 (1999); http://dx.doi.org/10.1063/1.125360 (3 pages) | Cited 8 times

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Doped with nanometer Au particles, a low-Tg photorefractive polymer composite, poly(N-vinylcarbazole):2,4,7-trinitro-9-fluorenone:4-(dicyanovinyl-N,N-diethylaniline), exhibited an effective enhancement on its photorefractivity. Measurements on two-beam coupling (TBC) as well as four-wave mixing were carried out at 633 nm wavelength. At an applied electric field of 118 V/μm, TBC coefficient as high as 206 cm−1 was obtained in the sample doped with Au particles, while only 152 cm−1 in the sample without Au particles. The measurements on the effective electro-optic coefficient and the photorefractive phase shift for two samples with and without doping Au particles were performed, respectively. The observations of distinct difference on the photorefractive phase shift and no difference on the effective electro-optic coefficient implied that enhancement on the photorefractivity was due to the increment of the density of the effective trap center by doping Au particles. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.20.Jq Electro-optical effects

Low-temperature near-field nonlinear absorption spectroscopy of InGaAs single quantum dots

Takuya Matsumoto, Motoichi Ohtsu, Kazunari Matsuda, Toshiharu Saiki, Hideaki Saito, and Kenichi Nishi

Appl. Phys. Lett. 75, 3246 (1999); http://dx.doi.org/10.1063/1.125313 (3 pages) | Cited 15 times

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Nonlinear absorption spectroscopy of InGaAs single quantum dots (QDs) was realized by means of a low-temperature near-field optical microscope. The spatial distribution of the nonlinear absorption change in single QDs was determined. The dependence of the nonlinear absorption change on the pump power density demonstrates that the nonlinearity originates from the state filling of the ground state. The nonlinear absorption spectrum showed a homogeneous broadening of the ground state of about 5 meV. Furthermore, the change in the absorption cross section of the single QD when the ground state is saturated with carriers is estimated to be 2.8±0.6 nm2, which agrees with the result predicted on the basis of theoretical consideration. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
07.79.Fc Near-field scanning optical microscopes

Nonlinear optical effects in chalcogenide photoresists

G. Rosenblum, B. G. Sfez, Z. Kotler, V. Lyubin, and M. Klebanov

Appl. Phys. Lett. 75, 3249 (1999); http://dx.doi.org/10.1063/1.125314 (3 pages) | Cited 11 times

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Both the “after-pulse effect” and the dynamic characteristics of photostructural transformations induced in glassy As0.5Se0.5 films by pulsed 532 nm excitation have been studied. The after-pulse effect investigation demonstrated more than a 103 times increase of the photosensitivity in case of pulsed excitation. Dynamic characteristics showed a dual time scale behavior and different intensity dependence of transient and long time scale signals. The obtained data indicate that the strong increase of photosensitivity following short intense pulsed light excitation is due to a two-photon effect that aids the process of structural rearrangement. © 1999 American Institute of Physics.
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42.65.-k Nonlinear optics
61.43.Fs Glasses
85.40.Hp Lithography, masks and pattern transfer
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
64.70.K- Solid-solid transitions
61.82.Fk Semiconductors
42.70.Gi Light-sensitive materials

Molecular organic light-emitting diodes with temperature-independent quantum efficiency and improved thermal durability

Hideyuki Murata, Charles D. Merritt, Hiroshi Inada, Yasuhiko Shirota, and Zakya H. Kafafi

Appl. Phys. Lett. 75, 3252 (1999); http://dx.doi.org/10.1063/1.125315 (3 pages) | Cited 18 times

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We demonstrate efficient and thermally stable molecular light-emitting diodes based on a multilayered structure that consists of two hole transport layers with high glass-transition temperatures, and an emitting layer doped with a highly fluorescent dye. Stable device operation was achieved up to 90° C. By using an emitting layer doped with a highly fluorescent dye, the electroluminescence quantum efficiency reaches 2.2% and does not decrease with increasing temperature in contrast to a device with an undoped emitting layer. The luminous efficiency at 100 cd/m2 increases from 4.6 lm/W at room temperature to 7.5 lm/W at 90 °C. The half-decay time of the initial luminance (∼800 cd/m2) of the devices is 3200 h (room temperature) and 200 h (80 °C) at constant dc current (10 mA/cm2). © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices

Adaptive all-order dispersion compensation of ultrafast laser pulses using dynamic spectral holography

Y. Ding, A. M. Weiner, M. R. Melloch, and D. D. Nolte

Appl. Phys. Lett. 75, 3255 (1999); http://dx.doi.org/10.1063/1.125316 (3 pages) | Cited 8 times

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The time-varying dispersion of ultrafast laser pulses can be self-adaptively stabilized using real-time dynamic spectral holography in semiconductor photorefractive quantum wells. Dispersion of all orders is compensated by forming a dynamic spectral-domain hologram of a signal pulse (that has a time-varying dispersion) referenced to a stable clock pulse. The hologram is read out using forward-scattering phase conjugation to remove phase distortion to all orders, including drift in the time of flight. We have achieved adaptive cancellation of time-of-flight excursions up to ±15 ps to an accuracy of ±15 fs with a compensation bandwidth of 1 kHz. © 1999 American Institute of Physics.
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42.40.My Applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Gi Light-sensitive materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Phonon enhanced inverse population in asymmetric double quantum wells

Michael A. Stroscio, Mikhail Kisin, Gregory Belenky, and Serge Luryi

Appl. Phys. Lett. 75, 3258 (1999); http://dx.doi.org/10.1063/1.125317 (3 pages) | Cited 15 times

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Interwell optical-phonon-assisted transitions are studied in an asymmetric double-quantum-well heterostructure comprising one narrow and one wide coupled quantum wells (QWs). We show that the depopulation rate of the lower subband states in the narrow QW can be significantly enhanced thus facilitating the intersubband inverse population, if the depopulated subband is aligned with the second subband of the wider QW, while the energy separation from the first subband is tuned to the highest energy optical-phonon mode. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.38.-k Polarons and electron-phonon interactions
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Effects of interference in quasiphase-matched periodically segmented potassium titanyl phosphate waveguides

Zachary S. Benaich, Ranjit D. Pradhan, Shabbir M. Mian, and Noureddine Melikechi

Appl. Phys. Lett. 75, 3261 (1999); http://dx.doi.org/10.1063/1.125318 (3 pages) | Cited 5 times

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We show that optical interference of two input beams coupled into a periodically segmented KTiOPO4 waveguide can increase the efficiency of the generated second harmonic by a factor of three over coupling a single beam with the same total power. A simple model based on two interfering Gaussian beams indicates that the second harmonic output increases by enhancing the coupling of the fundamental energy into the waveguide. A Mach–Zehnder interferometer scheme is used to demonstrate this effect. The variation of the second harmonic power with the fundamental input power of the interfering beams shows excellent qualitative agreement between experimental results and the model presented. © 1999 American Institute of Physics.
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42.25.Hz Interference
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides

Enhanced dynamic response of the in-plane switching liquid crystal display mode through polymer stabilization

Michael J. Escuti, Chris C. Bowley, Gregory P. Crawford, and Slobodan Žumer

Appl. Phys. Lett. 75, 3264 (1999); http://dx.doi.org/10.1063/1.125319 (3 pages) | Cited 27 times

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A significant improvement in the dynamic response time of the in-plane switching nematic liquid crystal mode, useful in flat-panel display applications, is achieved through polymer stabilization. This improvement is achieved by introducing a low-density, stabilizing polymer network that causes the nematic director to favor the zero-field orientation at the expense of transmission and slightly higher drive voltages. We present a simple model that treats the polymer network as an effective field in the general framework of elastic continuum theory. © 1999 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Room-temperature continuous-wave operation of a single-layered 1.3 μm quantum dot laser

Gyoungwon Park, Oleg B. Shchekin, Sebastion Csutak, Diana L. Huffaker, and Dennis G. Deppe

Appl. Phys. Lett. 75, 3267 (1999); http://dx.doi.org/10.1063/1.125320 (3 pages) | Cited 86 times

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Room-temperature continuous-wave operation of a 1.3 μm quantum dot laser is reported. The threshold current for a single layer active region with p–up mounting is only 4.1 mA with a threshold current density of 45 A/cm2. The minimum room temperature threshold current density is 25 A/cm2 for pulsed operation. Cryogenic and temperature dependent measurements are performed on broad-area lasers fabricated from the same active material. At 4 K the broad-area threshold current density for uncoated facets is 6 A/cm2. © 1999 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Pk Continuous operation

Blue polymer light-emitting diodes from poly(9,9-dihexylfluorene-alt-co-2, 5-didecyloxy-para-phenylene)

Wang-Lin Yu, Yong Cao, Jian Pei, Wei Huang, and Alan J. Heeger

Appl. Phys. Lett. 75, 3270 (1999); http://dx.doi.org/10.1063/1.125321 (3 pages) | Cited 51 times

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Deep blue photoluminescence and electroluminescence are demonstrated from a soluble conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-para-phenylene). The PL quantum efficiency is approximately 40%. Cyclic voltammetry measurements indicate that the highest occupied molecular orbital and lowest unoccupied molecular orbital energies are 5.66 and 2.62 eV below vacuum, respectively. Single-layer and multilayer light-emitting diodes emit deep blue light (peak at ∼420 nm). © 1999 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.55.Kz Solid organic materials
42.70.Jk Polymers and organics
82.80.Fk Electrochemical methods
71.20.Rv Polymers and organic compounds

Selective excitation and thermal quenching of the yellow luminescence of GaN

J. S. Colton, P. Y. Yu, K. L. Teo, E. R. Weber, P. Perlin, I. Grzegory, and K. Uchida

Appl. Phys. Lett. 75, 3273 (1999); http://dx.doi.org/10.1063/1.125322 (3 pages) | Cited 16 times

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We report the observation of narrower structures in the yellow luminescence of bulk and thin-film n-type GaN, using the technique of selective excitation. These fine structures exhibit thermal quenching associated with an activated behavior. We attribute these fine structures to phonons and electronic excitations of a shallow donor-deep acceptor complex, and determine its activation energy for delocalization. Our results suggest that in addition to distant donor-acceptor pairs, the yellow luminescence can also involve emission complexes of shallow donors and deep acceptors. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
63.20.K- Phonon interactions

A visible–near infrared range photonic crystal made up of Si nanopillars

Vladimir V. Poborchii, Tetsuya Tada, and Toshihiko Kanayama

Appl. Phys. Lett. 75, 3276 (1999); http://dx.doi.org/10.1063/1.125323 (3 pages) | Cited 26 times

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We studied a two-dimensional square lattice of Si nanopillars (SQLN) perspective for applications in waveguides. Reflection spectra of SQLN with the period of 270 nm were studied for different surrounding media, namely air and water. SQLN is shown to display photonic band gap (PBG) behavior in the visible–infrared spectral range. The energy positions and widths of the experimentally observed reflection bands are found to be in agreement with calculated PBG. © 1999 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
78.40.Fy Semiconductors
78.30.Am Elemental semiconductors and insulators
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