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19 Apr 1999

Volume 74, Issue 16, pp. 2253-2392

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Direct observation of orientation limit in a fast photorefractive polymer composite

J. A. Herlocker, K. B. Ferrio, E. Hendrickx, B. D. Guenther, S. Mery, B. Kippelen, and N. Peyghambarian

Appl. Phys. Lett. 74, 2253 (1999); http://dx.doi.org/10.1063/1.123816 (3 pages) | Cited 51 times

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We report on a photorefractive polymer with a 4-ms-response time in transient four-wave mixing experiments at 0.5 W/cm2 writing irradiance, 95 V/μm applied electric field, and a grating period of 3.1 μm. Complementary transient ellipsometry, however, reveals orientational birefringence response which leads the four-wave mixing response all the way to its saturation, despite complex dynamics in these processes. Orientation does not limit the dynamic formation of photorefractive gratings in this polymer, which suggests that even faster photorefractive responses are possible for polymer composites with improved charge generation and transport properties. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Jk Polymers and organics
42.70.Gi Light-sensitive materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Dj Gratings
78.20.Fm Birefringence
78.20.Jq Electro-optical effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics

Light-emitting diodes with 31% external quantum efficiency by outcoupling of lateral waveguide modes

R. Windisch, P. Heremans, A. Knobloch, P. Kiesel, G. H. Döhler, B. Dutta, and G. Borghs

Appl. Phys. Lett. 74, 2256 (1999); http://dx.doi.org/10.1063/1.123817 (3 pages) | Cited 73 times

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The external quantum efficiency of light-emitting diodes (LEDs) is usually limited by total internal reflection at the semiconductor–air interface. This problem can be overcome by a combination of light scattering at a textured top surface and reflection on a backside mirror. With this design, we achieve 22% external quantum efficiency. One of the main loss mechanisms in such nonresonant cavity (NRC) light-emitting diodes is coupling into an internal waveguide. Texturing the surface of this waveguide allows the partial extraction of the confined light. In this way, we demonstrate an increase in the external quantum efficiency of NRC-LEDs to 31%. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.79.Gn Optical waveguides and couplers

Broad-range, latchable reconfiguration of Bragg wavelength in optical gratings

S. Jin, H. Mavoori, R. P. Espindola, and T. A. Strasser

Appl. Phys. Lett. 74, 2259 (1999); http://dx.doi.org/10.1063/1.123818 (3 pages) | Cited 7 times

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Tunability of optical signal filters such as fiber Bragg gratings is important for high volume data communications. A magnetically tunable and latchable optical fiber Bragg grating structure has been devised, and a fine wavelength control as well as a broad-range wavelength tunability has been demonstrated. A spinodally decomposed, anisotropically elongated microstructure was induced in Fe–Cr–Co alloys to fabricate square-loop, programmable magnets. The adjustable attractive force between the magnetic poles was used to controllably strain the grating and induce a very large shift in the Bragg reflection wavelength by as much as 15 nm (which is equivalent to more than 36-channel span in a high density optical communication system). This novel approach can be useful not only for a variety of optical communication networking applications, but also for imparting latchable reconfiguration of structural periodicity and functional properties in a wide class of materials and devices. © 1999 American Institute of Physics.
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42.81.Wg Other fiber-optical devices
42.79.Dj Gratings
42.79.Ci Filters, zone plates, and polarizers
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
84.40.Ua Telecommunications: signal transmission and processing; communication satellites

Blue luminescence from amorphous GaN nanoparticles synthesized in situ in a polymer

Yi Yang, Valerie J. Leppert, Subhash H. Risbud, Brendan Twamley, Phillip P. Power, and Howard W. H. Lee

Appl. Phys. Lett. 74, 2262 (1999); http://dx.doi.org/10.1063/1.123819 (3 pages) | Cited 31 times

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Amorphous GaN nanoparticles were synthesized by the in situ thermal decomposition of cyclotrigallazane incorporated into a polystyrene–poly(N,N-dimethyl-4-vinylaniline) copolymer. Transmission electron microscopy, energy dispersive x-ray spectrometry, and x-ray photoelectron spectroscopy show that the composite material consists of amorphous GaN nanoparticles (average diameter ∼40 nm) well dispersed in the copolymer. The photoluminescence spectra show blue light emission from the amorphous GaN nanoparticles, peaked at ∼426 nm. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

High performance organic polymer light-emitting heterostructure devices

Y. He, S. Gong, R. Hattori, and J. Kanicki

Appl. Phys. Lett. 74, 2265 (1999); http://dx.doi.org/10.1063/1.123862 (3 pages) | Cited 61 times

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We report a high performance electroluminescence device based on bi-layer conjugated polymer structures consisting of a hole transporting (amine-fluorene) and an emissive (benzothiadiazole-fluorene) polymer layers prepared by the spin-coating technique on the glass substrate. Devices showed green emission with an electroluminescence peak located at around 545 nm and a full width at half maximum of about 80 nm. Our devices have also shown a high brightness ( ∼ 10 000 cd/m2 at 0.84 mA/mm2), good emission efficiency ( ∼ 14.5 cd/A) and luminous efficiency (2.26 lm/W), a large external quantum efficiency (3.8%), and a reasonable forward-to-reverse bias current rectification ratio (>103 at ±25 V). © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds
73.61.Ph Polymers; organic compounds
73.40.Ei Rectification

Sub-5-fs visible pulse generation by pulse-front-matched noncollinear optical parametric amplification

A. Shirakawa, I. Sakane, M. Takasaka, and T. Kobayashi

Appl. Phys. Lett. 74, 2268 (1999); http://dx.doi.org/10.1063/1.123820 (3 pages) | Cited 125 times

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Sub-5-fs pulses are generated in the visible region. A pulse-front-matched noncollinear optical parametric amplifier is operated with the full bandwidth by precompression of the seeded continuum with a customized ultrabroadband chirped mirror (UBCM) pair. The signal is compressed down to a nearly transform-limited 4.7±0.1 fs duration by a prism pair and another UBCM pair with a 5-μJ pulse energy. © 1999 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Yj Optical parametric oscillators and amplifiers
42.79.Bh Lenses, prisms and mirrors
42.60.Fc Modulation, tuning, and mode locking

Ultrafast (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser for the 1.3 μm wavelength regime

C. Ellmers, F. Höhnsdorf, J. Koch, C. Agert, S. Leu, D. Karaiskaj, M. Hofmann, W. Stolz, and W. W. Rühle

Appl. Phys. Lett. 74, 2271 (1999); http://dx.doi.org/10.1063/1.123821 (3 pages) | Cited 42 times

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(GaIn)(NAs) vertical-cavity surface-emitting lasers for room-temperature emission at 1.3 μm wavelength are designed and grown by metal-organic vapor-phase epitaxy using dimethylhydrazine and tertiarybutylarsine. Room-temperature operation at wavelengths up to 1.285 μm is achieved with low optical pumping thresholds between 1.6 and 2.0 kW/cm2. Stimulated emission dynamics after femtosecond optical pumping are measured and compare favorably with results on (GaIn)As/Ga(PAs)-based structures. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.45.+h Stimulated emission
78.66.Fd III-V semiconductors

Polarization modal noise and dichroism in vertical-cavity semiconductor lasers

M. P. van Exter, M. B. Willemsen, and J. P. Woerdman

Appl. Phys. Lett. 74, 2274 (1999); http://dx.doi.org/10.1063/1.123822 (3 pages) | Cited 10 times

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We show quantitatively how the limited polarization stability of vertical-cavity semiconductor lasers is related to the small dichroism and large quantum noise in these lasers. We introduce several techniques to measure this dichroism and noise. Suitable polarization projections are shown to yield either the heterodyne beat or the partition noise of the two polarization modes. © 1999 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.Mi Dynamical laser instabilities; noisy laser behavior
42.50.Lc Quantum fluctuations, quantum noise, and quantum jumps
78.20.Fm Birefringence
78.66.Fd III-V semiconductors

Clamping of the linewidth enhancement factor in narrow quantum-well semiconductor lasers

J. Hader, D. Bossert, J. Stohs, W. W. Chow, S. W. Koch, and J. V. Moloney

Appl. Phys. Lett. 74, 2277 (1999); http://dx.doi.org/10.1063/1.123823 (3 pages) | Cited 21 times

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The linewidth enhancement factor in single quantum-well graded index separate confinement heterostructure semiconductor lasers is investigated theoretically and experimentally. For thin wells, a small linewidth enhancement factor is obtained which clamps with increasing carrier density, in contrast to the monotonous increase observed for thicker wells. Microscopic many-body calculations reproduce the experimental observations attributing the clamping to excitation dependent gain shifts and the influence of the population of off-resonant states on the refractive index. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Ry Gradient-index (GRIN) devices
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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