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20 Sep 2010

Volume 97, Issue 12, Articles (12xxxx)

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Appl. Phys. Lett. 97, 123101 (2010); http://dx.doi.org/10.1063/1.3490637 (3 pages)

Mark W. Licurse and Peter K. Davies
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Large optical bandwidth and polarization insensitive semiconductor optical amplifiers using strained InGaAsP quantum wells

H. Carrère, V. G. Truong, X. Marie, R. Brenot, G. De Valicourt, F. Lelarge, and T. Amand

Appl. Phys. Lett. 97, 121101 (2010); http://dx.doi.org/10.1063/1.3484151 (3 pages)

Online Publication Date: 20 September 2010

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The material gain of equal width InGaAsP/InGaAsP multi–quantum well active layers is calculated solving the Lüttinger–Kohn Hamiltonian, including tetragonal strain and confinement effects. The calculated optical bandwidth reaches 150 nm with a maximum polarization sensitivity of 1 dB between transverse electric (TE) and transverse magnetic (TM) emission over the −3 dB optical bandwidth. The corresponding device characterized by amplified spontaneous emission measurements shows an optical bandwidth with constant TE/TM ratio of almost 100 nm which can be improved up to 113 nm by increasing the barrier material band gap energy. Further enlargement of the optical bandwidth is expected by reducing the quantum well width.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
68.65.Fg Quantum wells

Temperature dependence of electronic transitions and optical properties in multiferroic BiFeO3 nanocrystalline film determined from transmittance spectra

W. W. Li (李文武), J. J. Zhu (诸佳俊), J. D. Wu (吴嘉达), J. Gan (干洁), Z. G. Hu (胡志高), M. Zhu (朱敏), and J. H. Chu (褚君浩)

Appl. Phys. Lett. 97, 121102 (2010); http://dx.doi.org/10.1063/1.3489926 (3 pages) | Cited 10 times

Online Publication Date: 21 September 2010

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The ultraviolet-infrared transmittance spectra of BiFeO3 nanocrystalline film have been studied in the temperature range 5.3–300 K. A redshift trend of the absorption edge and optical constants with increasing the temperature can be observed. Four interband electronic transitions can be uniquely assigned and strongly depend on the temperature. Moreover, two magnetic transitions located at about 150 and 200 K have been observed and can be interpreted as spin-reorientation transitions. It was found that the optical band gap decreases from 2.69±0.01 to 2.65±0.01 eV with increasing the temperature due to the modification of the electron-phonon interactions.
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77.55.Nv Multiferroic/magnetoelectric films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
75.85.+t Magnetoelectric effects, multiferroics

Induced absorption dynamics in quantum dot based waveguide electroabsorbers

T. Piwonski, J. Pulka, E. A. Viktorov, G. Huyet, R. J. Manning, J. Houlihan, P. Mandel, and T. Erneux

Appl. Phys. Lett. 97, 121103 (2010); http://dx.doi.org/10.1063/1.3491805 (3 pages) | Cited 1 time

Online Publication Date: 22 September 2010

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Two-color pump-probe measurements are used to study the carrier dynamics of InAs/GaAs quantum dots in a waveguide structure under reverse bias conditions. For the case of initially populating the ground state (GS), we find relaxation dynamics that include both absorptive and bleaching components in the excited state (ES) wavelength range. We reproduce the main features of this induced absorption dynamics using a simple model with an additional term for induced absorption at the ES due to carriers injected at the GS. The induced absorption dynamics includes multiple recovery timescales which can be attributed to phonon-assisted processes of GS/ES interaction.
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77.22.Gm Dielectric loss and relaxation
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds

Long-period fiber gratings spontaneously written by a mechanism markedly different from Hill grating formation

H. Tu, S. Shin, R. John, and S. A. Boppart

Appl. Phys. Lett. 97, 121104 (2010); http://dx.doi.org/10.1063/1.3491842 (3 pages) | Cited 1 time

Online Publication Date: 22 September 2010

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Pumping a nonlinear germanosilicate fiber with intense near-infrared femtosecond laser pulses for supercontinuum generation may invoke multiphoton-assisted photosensitivity of glasses to write a long-period fiber grating. In sharp contrast to the spontaneous formation of a Hill grating that resonates with the writing wavelength through first-order diffraction, the long-period fiber grating resonates with the writing wavelength through second-order diffraction. This finding highlights the surprising light-matter interaction in a waveguide.
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42.81.Wg Other fiber-optical devices
42.79.Dj Gratings
42.65.-k Nonlinear optics

Internal efficiency of InGaN light-emitting diodes: Beyond a quasiequilibrium model

W. W. Chow, M. H. Crawford, J. Y. Tsao, and M. Kneissl

Appl. Phys. Lett. 97, 121105 (2010); http://dx.doi.org/10.1063/1.3490232 (3 pages) | Cited 6 times

Online Publication Date: 23 September 2010

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We propose a model to better investigate InGaN light-emitting diode (LED) internal efficiency by extending beyond the usual total carrier density rate equation approach. To illustrate its capability, the model is applied to study intrinsic performance differences between violet and green LEDs. The simulations show performance differences, at different current densities and temperatures, arising from variations in spontaneous emission and heat loss rates. By tracking the momentum-resolved carrier populations, these rate changes are, in turn, traced to differences in bandstructure and plasma heating. The latter leads to carrier distributions that deviate from the quasiequilibrium ones at lattice temperature.
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85.60.Jb Light-emitting devices
85.30.De Semiconductor-device characterization, design, and modeling

High-sensitivity detection of terahertz waves using nonlinear up-conversion in an organic 4-dimethylamino-N-methyl-4-stilbazolium tosylate crystal

Hiroaki Minamide, Jun Zhang, Ruixiang Guo, Katsuhiko Miyamoto, Seigo Ohno, and Hiromasa Ito

Appl. Phys. Lett. 97, 121106 (2010); http://dx.doi.org/10.1063/1.3489097 (3 pages) | Cited 1 time

Online Publication Date: 23 September 2010

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We achieved high-sensitivity, rapid-response detection of terahertz (THz) waves using an organic nonlinear optical crystal, 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST). Nonlinear up-conversion in the crystal resulted in a shift of THz waves to near-infrared radiation at room temperature. A minimum THz-wave peak power of about 300 μW was measured at 19.2 THz by detecting the up-converted optical signal with an InGaAs-based photodetector. A noise equivalent power of about 6 nW/Hz1/2 was estimated in this experiment. Optimum conditions were obtained for THz-wave detection using a DAST crystal.
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42.65.-k Nonlinear optics
78.30.-j Infrared and Raman spectra
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)

Enhancement of light power for strain-compensated hybrid InGaN/InGaN/MgZnO light-emitting diodes

Seoung-Hwan Park, Yong-Tae Moon, Jeong Sik Lee, Ho Ki Kwon, Joong Seo Park, and Doyeol Ahn

Appl. Phys. Lett. 97, 121107 (2010); http://dx.doi.org/10.1063/1.3493648 (3 pages)

Online Publication Date: 23 September 2010

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Electronic and optical properties of strain-compensated InGaN/InGaN/MgZnO quantum well (QW) structures using a MgZnO substrate are investigated using the multiband effective mass theory. A strain-compensated InGaN/InGaN/MgZnO QW structure with a larger strain shows larger matrix element than that with a smaller strain. The spontaneous emission peak rapidly increases with increasing compressive strain because the matrix element is enhanced for the strain-compensated QW structure with a larger strain. In addition, we find that the strain-compensated QW structure with the larger Mg composition in the substrate has greater spontaneous emission peak than the strain-compensated QW structure with the smaller Mg composition in the substrate.
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85.60.Jb Light-emitting devices

Multicolor fluorescence enhancement from a photonics crystal surface

A. Pokhriyal, M. Lu, C. S. Huang, S. Schulz, and B. T. Cunningham

Appl. Phys. Lett. 97, 121108 (2010); http://dx.doi.org/10.1063/1.3485672 (3 pages) | Cited 2 times

Online Publication Date: 24 September 2010

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A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ∼ 3×5 in.2 surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ = 632.8 nm laser (cyanine-5) and a dye excited by a λ = 532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays.
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87.15.mq Luminescence
87.80.-y Biophysical techniques (research methods)

An efficiently tunable microring resonator using a liquid crystal-cladded polymer waveguide

Tao Cai, Qingkun Liu, Yaocheng Shi, Pengxin Chen, and Sailing He

Appl. Phys. Lett. 97, 121109 (2010); http://dx.doi.org/10.1063/1.3492848 (3 pages)

Online Publication Date: 24 September 2010

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An electrically tunable polymer microring resonator of large tunability and low applied voltage is demonstrated using active liquid crystal (LC) cladding. A large tuning range of 0.73 nm is achieved due to more homogenous LC molecular alignment and enhanced interaction of the light with the LC cladding in the simplified polymer waveguide structure. The operating voltage decreases to 10 V with a threshold of only 3 V by the utilization of interdigital electrodes.
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42.79.Gn Optical waveguides and couplers
42.70.Df Liquid crystals
07.10.Cm Micromechanical devices and systems

Temperature dependence of electroabsorption dynamics in an InAs quantum-dot saturable absorber at 1.3 μm and its impact on mode-locked quantum-dot lasers

M. A. Cataluna, D. B. Malins, A. Gomez-Iglesias, W. Sibbett, A. Miller, and E. U. Rafailov

Appl. Phys. Lett. 97, 121110 (2010); http://dx.doi.org/10.1063/1.3489104 (3 pages) | Cited 3 times

Online Publication Date: 24 September 2010

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We report temperature-dependent absorption recovery times in an InAs p-i-n ridge waveguide quantum-dot modulator under low reverse bias, investigated via subpicosecond pump-probe measurements. The measured decrease in absorption recovery time with increasing temperature (293–319 K) is in excellent agreement with a thermionic emission model. A similar trend in pulse duration with increasing temperature is also observed from a two-section mode-locked quantum-dot laser fabricated from a similar epitaxial structure. These measurements confirm the key role of the absorber recovery time in the reduction in the pulses generated by two-section mode-locked quantum-dot lasers, both at room and elevated temperatures.
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42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Reduction in surface recombination and enhancement of light emission in silicon photonic crystals treated by high-pressure water-vapor annealing

Masayuki Fujita, Bernard Gelloz, Nobuyoshi Koshida, and Susumu Noda

Appl. Phys. Lett. 97, 121111 (2010); http://dx.doi.org/10.1063/1.3489419 (3 pages) | Cited 3 times

Online Publication Date: 24 September 2010

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We propose and demonstrate the application of high-pressure water-vapor annealing (HWA) to silicon photonic crystals for surface passivation. We find that the photoluminescence intensity from a sample treated with HWA is enhanced by a factor of ∼ 6. We confirm that this enhancement originates from a reduction in the surface-recombination velocity (SRV) by a factor of ∼ 0.4. The estimated SRV is as low as 2.1×103 cm/s at room temperature. These results indicate that HWA is a promising approach for efficient surface passivation in silicon photonic nanostructures.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
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