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31 Oct 2011

Volume 99, Issue 18, Articles (18xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 183701 (2011); http://dx.doi.org/10.1063/1.3656020 (3 pages)

V. Zablotskii, O. Lunov, A. Dejneka, L. Jastrabík, T. Polyakova, T. Syrovets, and Th. Simmet
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Light emission enhancement in blue InGaAlN/InGaN quantum well structures

Seoung-Hwan Park, Yong-Tae Moon, Dae-Seob Han, Joong Seo Park, Myeong-Seok Oh, and Doyeol Ahn

Appl. Phys. Lett. 99, 181101 (2011); http://dx.doi.org/10.1063/1.3657141 (3 pages) | Cited 3 times

Online Publication Date: 31 October 2011

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Optical properties of blue AlInGaN/InGaN quantum well (QW) structures with a quaternary AlInGaN well layer were investigated by using the non-Markovian gain model with many-body effects. The band-gap expression of the AlInGaN materials was determined through a comparison with experimental results. We found that the emission peak can be enhanced by using quaternary AlInGaN well and is sensitive on In composition in the InGaN barrier. For example, the spontaneous emission coefficient for Al0.08In0.22Ga0.67 N/InxGa1−xN QW structures shows a maximum at In composition of 0.13 in the barrier and gradually decreases with increasing In composition. This is attributed to the fact that the quasi-Fermi-level separation linearly decreases with increasing In composition in the barrier due to the decrease in the conduction and valence band offsets. The AlInGaN/InGaN system with zero internal field is found to have smaller emission peak than the AlInGaN/InGaN system with nonzero internal field due to smaller band offsets.
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78.67.De Quantum wells
81.05.Ea III-V semiconductors
81.07.St Quantum wells
71.20.Nr Semiconductor compounds
73.21.Fg Quantum wells

High-performance, long-wave (∼10.2 μm) InGaAs/GaAs quantum dot infrared photodetector with quaternary In0.21Al0.21Ga0.58As capping

Subhananda Chakrabarti, Sourav Adhikary, Nilanjan Halder, Yigit Aytac, and A. G. U. Perera

Appl. Phys. Lett. 99, 181102 (2011); http://dx.doi.org/10.1063/1.3657142 (3 pages) | Cited 9 times

Online Publication Date: 31 October 2011

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A high-performance InGaAs/GaAs vertical quantum dot infrared photodetector (QDIP) with combined barrier of quaternary In0.21Al0.21Ga0.58As and GaAs was investigated in this study. A dominant long wavelength (∼10.2 μm) response was observed from the device. The device demonstrates large responsivity (2.16 A/W) with narrow spectral-width (Δλ/λ ∼0.14) and high detectivity (1.01 × 1011 cm Hz1/2/W at 0.3 V) at 10.2 μm at 77 K. In addition, the device has also produced a detectivity in the order of 6.4 × 1010 cm Hz1/2/W at 100 K at a bias of 0.2 V, indicating its suitability for high-temperature operations.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.De Semiconductor-device characterization, design, and modeling

Efficient continuous wave deep ultraviolet Pr3+:LiYF4 laser at 261.3 nm

Teoman Gün, Philip Metz, and Günter Huber

Appl. Phys. Lett. 99, 181103 (2011); http://dx.doi.org/10.1063/1.3657150 (3 pages) | Cited 4 times

Online Publication Date: 31 October 2011

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We report continuous wave deep ultraviolet laser operation at 261.3 nm by intracavity frequency doubling of laser diode pumped Pr3+ doped LiYF4 lasers. Using two InGaN laser diodes with a maximum output power of about 1 W each, a 2.9 mm long Pr3+:LiYF4 crystal and a 5 mm long beta-barium-borate crystal, coherent radiation with an output power of 481 mW at 261.3 nm was achieved at an optical-to-optical efficiency of 26.1% with respect to the total pump power. Both, linear and nonlinear losses have been calculated to be approximately 0.6% by using a model for intracavity frequency doubling with focussed Gaussian beams.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.-e Optical elements, devices, and systems

Directivity and isotropic band-gap in 12-fold symmetry plasmonic quasi-crystals with small index contrast

C. J. Regan, L. Grave de Peralta, and A. A. Bernussi

Appl. Phys. Lett. 99, 181104 (2011); http://dx.doi.org/10.1063/1.3657498 (3 pages) | Cited 1 time

Online Publication Date: 31 October 2011

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We experimentally investigated the map of the momentum of photons of propagating modes in dye-doped dielectric loaded plasmonic quasi-crystals with 12-fold symmetry. Using Fourier plane image analysis we established the relation between the pseudo-Brillouin zone and the directivity of propagating modes in plasmonic quasi-crystals with different periods at different frequencies. We demonstrated that a full isotropic bandgap can be achieved with the proposed structures.
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71.20.Rv Polymers and organic compounds
71.23.Ft Quasicrystals
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Plasmonic reflection grating back contacts for microcrystalline silicon solar cells

U. W. Paetzold, E. Moulin, D. Michaelis, W. Böttler, C. Wächter, V. Hagemann, M. Meier, R. Carius, and U. Rau

Appl. Phys. Lett. 99, 181105 (2011); http://dx.doi.org/10.1063/1.3657513 (3 pages) | Cited 21 times

Online Publication Date: 31 October 2011

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We report on the fabrication and optical simulation of a plasmonic light-trapping concept for microcrystalline silicon solar cells, consisting of silver nanostructures arranged in square lattice at the ZnO:Al/Ag back contact of the solar cell. Those solar cells deposited on this plasmonic reflection grating back contact showed an enhanced spectral response in the wavelengths range from 500 nm to 1000 nm, when comparing to flat solar cells. For a particular period, even an enhancement of the short circuit current density in comparison to the conventional random texture light-trapping concept is obtained. Full three-dimensional electromagnetic simulations are used to explain the working principle of the plasmonic light-trapping concept.
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88.40.jj Silicon solar cells
88.40.H- Solar cells (photovoltaics)

Dipole-dipole interaction in a quantum dot and metallic nanorod hybrid system

Mahi R. Singh, Daniel G. Schindel, and Ali Hatef

Appl. Phys. Lett. 99, 181106 (2011); http://dx.doi.org/10.1063/1.3658395 (3 pages) | Cited 10 times

Online Publication Date: 1 November 2011

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We have studied quantum coherence and interference phenomena in a quantum dot (QD)-metallic nanorod (MNR) hybrid system. Probe and control laser fields are applied to the hybrid system. Induced dipole moments are created in the QD and the MNR, and they interact with each other via the dipole-dipole interaction. Using the density matrix method, it was found that the power spectrum of MNR has two transparent, states and they can be switched to one transparent state by the control field. Ultrafast switching and sensing nanodevices could be produced using this model.
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73.23.-b Electronic transport in mesoscopic systems
78.67.Hc Quantum dots
78.67.Qa Nanorods
42.62.-b Laser applications
68.35.Ct Interface structure and roughness
71.35.-y Excitons and related phenomena

Structurally dictated anisotropic “designer surface plasmons”

Helen J. Rance, Ian R. Hooper, Alastair P. Hibbins, and J. Roy Sambles

Appl. Phys. Lett. 99, 181107 (2011); http://dx.doi.org/10.1063/1.3655170 (3 pages) | Cited 1 time

Online Publication Date: 1 November 2011

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The concept of pseudo-plasmonic surfaces at microwave frequencies is extended to include structures with a high degree of surface anisotropy. The experimental sample is fabricated by patterning a metal with a rectangular array of rectangular holes and is found to support structurally dictated surface plasmon-like modes; the anisotropic dispersion of which results from an ellipsoid of limiting frequencies. By exploiting the anisotropy of the unit cell, the family of higher order surface waves associated with the quantization of the electromagnetic fields within the holes is also explored.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Graded-size Si quantum dot ensembles for efficient light-emitting diodes

A. Anopchenko, A. Marconi, M. Wang, G. Pucker, P. Bellutti, and L. Pavesi

Appl. Phys. Lett. 99, 181108 (2011); http://dx.doi.org/10.1063/1.3658625 (3 pages) | Cited 6 times

Online Publication Date: 1 November 2011

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We propose a simple way to engineer the energy band gap of an ensemble of silicon nanocrystal (Si-NC) embedded in SiO2 via thickness/composition profiling of Si-NC multilayers. By means of a complementary metal-oxide-semiconductor compatible process, light emitting diodes (LEDs) which incorporate graded energy gap Si-NC multilayers in the active region have been grown. Electrical and optical properties of these graded Si-NC LEDs demonstrate the ability of the proposed method to tailor the optoelectronic properties of Si-NC devices.
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81.05.Cy Elemental semiconductors
81.07.Ta Quantum dots
85.60.Jb Light-emitting devices
73.21.La Quantum dots
73.63.Kv Quantum dots
78.67.Hc Quantum dots

Competing influence of an in-plane electric field on the Stark shifts in a semiconductor quantum dot

T. Nakaoka, Y. Tamura, T. Saito, T. Miyazawa, K. Watanabe, Y. Ota, S. Iwamoto, and Y. Arakawa

Appl. Phys. Lett. 99, 181109 (2011); http://dx.doi.org/10.1063/1.3658639 (3 pages)

Online Publication Date: 1 November 2011

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We report on the fabrication of a side-gate structure which enables a purely lateral electric field to be applied onto a self-assembled quantum dot. The lateral field produces an unconventional “M’-shaped exciton energy shift—a blueshift followed by a redshift. The unconventional energy shift is reproduced by calculation. The calculation shows that only the positively charged exciton shows the unconventional shift. The origin is attributed to the field-induced hole-concentration in the bottom-corner of the dot, which strongly enhances the repulsive direct Coulomb interaction and reduces the exciton binding energy.
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78.67.Hc Quantum dots
81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.La Quantum dots

Waveguide superconducting single-photon detectors for integrated quantum photonic circuits

J. P. Sprengers, A. Gaggero, D. Sahin, S. Jahanmirinejad, G. Frucci, F. Mattioli, R. Leoni, J. Beetz, M. Lermer, M. Kamp, S. Höfling, R. Sanjines, and A. Fiore

Appl. Phys. Lett. 99, 181110 (2011); http://dx.doi.org/10.1063/1.3657518 (3 pages) | Cited 18 times

Online Publication Date: 1 November 2011

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The monolithic integration of single-photon sources, passive optical circuits, and single-photon detectors enables complex and scalable quantum photonic integrated circuits, for application in linear-optics quantum computing and quantum communications. Here, we demonstrate a key component of such a circuit, a waveguide single-photon detector. Our detectors, based on superconducting nanowires on GaAs ridge waveguides, provide high efficiency (∼20%) at telecom wavelengths, high timing accuracy (∼60 ps), and response time in the ns range and are fully compatible with the integration of single-photon sources, passive networks, and modulators.
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42.82.-m Integrated optics
42.50.-p Quantum optics

Broad spectral response in composition-graded CdSSe single nanowires via waveguiding excitation

Fuxing Gu, Huakang Yu, Wei Fang, and Limin Tong

Appl. Phys. Lett. 99, 181111 (2011); http://dx.doi.org/10.1063/1.3657523 (3 pages)

Online Publication Date: 1 November 2011

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We report broad spectral response in composition-graded CdSSe single nanowires (NWs) via waveguiding excitation. The excitation light is coupled to CdSSe single nanowires via silica fiber tapers. The guided photons in the nanowire with energies ranging from 1.74 to 2.44 eV can be efficiently captured at different sites along the NW length. Compared to single-composition nanowires, the composition-graded CdSSe nanowires exhibit much broader spectral response range, while retaining the detection limit down to sub-pW level. Utilizing the photoconductive quenching effect, the spectral range can be further extended beyond 1.5 μm with detection limit down to sub-nW level at room temperature.
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78.67.Uh Nanowires
42.70.-a Optical materials
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors

Tunable excitation source for coherent Raman spectroscopy based on a single fiber laser

Peter Adany, David C. Arnett, Carey K. Johnson, and Rongqing Hui

Appl. Phys. Lett. 99, 181112 (2011); http://dx.doi.org/10.1063/1.3657529 (3 pages) | Cited 2 times

Online Publication Date: 1 November 2011

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We demonstrate a wavelength tunable optical excitation source for coherent Raman scattering (CRS) spectroscopy based on a single femtosecond fiber laser. Electrically controlled wavelength tuning of Stokes optical pulses was achieved with soliton self frequency shift in an optical fiber, and linear frequency chirping was applied to both the pump and the Stokes waves to significantly improve the spectral resolution. The coherent anti-Stokes Raman scattering (CARS) spectrum of cyclohexane was measured and vibrational resonant Raman peaks separated by 70 cm−1 were clearly resolved. Single laser-based tunable excitation may greatly simplify CRS measurements and extend the practicality of CRS microscopy.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.55.Wd Fiber lasers
42.60.By Design of specific laser systems

Dilute-nitride GaInAsN/GaAs site-controlled pyramidal quantum dots

R. Carron, P. Gallo, B. Dwir, A. Rudra, and E. Kapon

Appl. Phys. Lett. 99, 181113 (2011); http://dx.doi.org/10.1063/1.3657770 (3 pages) | Cited 3 times

Online Publication Date: 1 November 2011

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GaInAsN quantum dots (QDs) were grown in inverted pyramids on a patterned (111)B GaAs surface. Incorporation of N in the active structure is attested to by a significant (∼80 meV) redshift of the photoluminescence spectrum of the QDs. Influence of the capillarity effect on the N incorporation is evidenced by comparing the redshift in the QD emission to that of its quantum wire (QWR) barriers. The significant increase in the inhomogeneous broadening of the InGaAsN QD arrays as compared to similar InGaAs QDs is explained by the large influence of a small number of N atoms and their configuration within the QD on its effective bandgap and confinement energy.
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68.65.Hb Quantum dots (patterned in quantum wells)
71.20.Nr Semiconductor compounds
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Kerr-driven nonlinear refractive index of air at 800 and 400 nm measured through femtosecond laser pulse filamentation

Yu. E. Geints, A. M. Kabanov, A. A. Zemlyanov, E. E. Bykova, O. A. Bukin, and S. S. Golik

Appl. Phys. Lett. 99, 181114 (2011); http://dx.doi.org/10.1063/1.3657774 (3 pages) | Cited 1 time

Online Publication Date: 1 November 2011

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The filamentation dynamics of 15 GW femtosecond laser pulses at 800 and 400 nm wavelengths upon their tight focusing in air is studied experimentally. The spatial position and extent of plasma channel formed within the filamentation zone as a function of laser pulse power are investigated. The processing of the experimental data according to the Marburger formula by J. H. Marburger [Prog. Quantum. Electron. 4, 35 (1975)] and the dispersion relations for air cubic nonlinearity has allowed to estimate the effective value of the Kerr-driven air refractive index on 400 nm as 5.36 × 10−19 cm2/W with a 5% error.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.-e Optical elements, devices, and systems

Promotion of hole injection enabled by GaInN/GaN light-emitting triodes and its effect on the efficiency droop

Sunyong Hwang, Woo Jin Ha, Jong Kyu Kim, Jiuru Xu, Jaehee Cho, and E. Fred Schubert

Appl. Phys. Lett. 99, 181115 (2011); http://dx.doi.org/10.1063/1.3658388 (3 pages) | Cited 2 times

Online Publication Date: 2 November 2011

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GaInN/GaN light-emitting triodes having two anodes for promoting the injection of holes into the active region were fabricated and characterized. It was found that the anode-to-anode bias modulates not only the hole-injection efficiency but also the effective light-emitting area and hence the current density through the active region. As the anode-to-anode bias increases, the efficiency at the same current density increases, whereas the efficiency droop decreases substantially, indicating that the limited hole-injection efficiency is one of the dominant mechanisms responsible for the efficiency droop in GaN-based light-emitting diodes.
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85.60.Jb Light-emitting devices
84.47.+w Vacuum tubes

Localized surface plasmon-enhanced electroluminescence from ZnO-based heterojunction light-emitting diodes

S. G. Zhang, X. W. Zhang, Z. G. Yin, J. X. Wang, J. J. Dong, H. L. Gao, F. T. Si, S. S. Sun, and Y. Tao

Appl. Phys. Lett. 99, 181116 (2011); http://dx.doi.org/10.1063/1.3658392 (3 pages) | Cited 14 times

Online Publication Date: 3 November 2011

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We demonstrate the surface plasmon (SP) enhanced n-ZnO/AlN/p-GaN light-emitting diodes (LEDs) by inserting the Ag nanoparticles (NPs) between the ZnO and AlN layers. The ultraviolet/violet near band edge emission of the device is significantly enhanced while the green defect-related emission is modestly suppressed compared to the LEDs without Ag NPs. The red-shift of electroluminescence (EL) peak and the reduced photoluminescence decay lifetime of ZnO suggest that the improved EL performance of the device with Ag NPs is attributed to the resonant coupling between excitons in ZnO and localized SPs in Ag NPs.
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85.60.Jb Light-emitting devices

Silver/silicon dioxide/silver sandwich films in the blue-to-red spectral regime with negative-real refractive index

Yi-Jun Jen, Akhlesh Lakhtakia, Ching-Wei Yu, Jheng-Jie Jhou, Wei-Hao Wang, Meng-Jie Lin, Huang-Ming Wu, and Hung-Sheng Liao

Appl. Phys. Lett. 99, 181117 (2011); http://dx.doi.org/10.1063/1.3658624 (3 pages) | Cited 2 times

Online Publication Date: 3 November 2011

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Sandwich films comprising arrays of silver/silicon-dioxide/silver nanosandwiches were grown by the oblique angle deposition technique. For normally incident light, these films present a negative-real refractive index (NRRI) over almost the entire visible regime, with quite high transparency and figures of merit, regardless of the orientation of the incident electric field. A broad distribution of nanosandwich sizes is responsible for the breadth of the NRRI spectral regime.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.-q Absorption and reflection spectra: visible and ultraviolet
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Thermal and optical characterization of resonant coupling between surface plasmon polariton and semiconductor waveguides

Joseph A. Summers and Rajeev J. Ram

Appl. Phys. Lett. 99, 181118 (2011); http://dx.doi.org/10.1063/1.3658733 (3 pages) | Cited 1 time

Online Publication Date: 3 November 2011

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Resonant coupling between an Au-InP surface plasmon polariton (SPP) and an InP/InGaAsP ridge waveguide is investigated. The general design requirements for evanescent coupling between a low-loss waveguide and a highly absorptive SPP are described, and experimental results are presented for fabricated devices. Coupling from the ridge to the SPP is confirmed using fiber-to-fiber optical power measurements, and thermoreflectance imaging is used to directly measure power coupled to the SPP along the length of the metal waveguide. The role of the thin native oxide at the Au-InP interface is also explored and found to have a significant impact on coupling.
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42.81.Qb Fiber waveguides, couplers, and arrays
42.82.Bq Design and performance testing of integrated-optical systems
07.60.-j Optical instruments and equipment
42.15.Eq Optical system design
42.81.Bm Fabrication, cladding, and splicing
42.81.Dp Propagation, scattering, and losses; solitons

Reversible and fast shift in reflection band of a cubic blue phase in a vertical electric field

Hui-Yu Chen, Ji-Yi Chiou, and Kai-Xian Yang

Appl. Phys. Lett. 99, 181119 (2011); http://dx.doi.org/10.1063/1.3658960 (3 pages) | Cited 2 times

Online Publication Date: 3 November 2011

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Two electro-optical phenomena of liquid-crystal blue phase with cubic lattice structure—(1) a fast and reversible shift in reflection band and (2) a phase transition from blue phase to chiral nematic phase—are observed in this study. By increasing the magnitude of a vertical electric field, the reflected wavelength of the blue phase can be shifted to a longer wavelength in a range of 80 nm within a few ms. This reflection band shift is induced by the reorientation of liquid-crystal molecules constructing double twist cylinders, which induces lattice distortion of the blue phase.
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78.15.+e Optical properties of fluid materials, supercritical fluids and liquid crystals
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
61.30.Mp Blue phases and other defect-phases
78.40.Dw Liquids
64.70.mj Experimental studies of liquid crystal transitions

Observation of ultra-narrow band plasmon induced transparency based on large-area hybrid plasmon-waveguide systems

Jing Zhang, Wenli Bai, Likang Cai, Yun Xu, Guofeng Song, and Qiaoqiang Gan

Appl. Phys. Lett. 99, 181120 (2011); http://dx.doi.org/10.1063/1.3659309 (3 pages) | Cited 6 times

Online Publication Date: 3 November 2011

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We report the observation of an ultra-narrow band plasmon induced transparency resonance which is realized in a large area hybrid plasmon-waveguide system consisting of a gold nanowire array embedded in a slab waveguide. Due to the destructive interference between optical modes supported by the hybrid system, an ultra-narrow plasmon induced transparency resonance with a bandwidth of 8 nm at the wavelength of 966 nm was obtained (i.e., ∼1/120 of the peak wavelength at the incident angle of 60°). The group velocity is estimated to be ∼76, which is promising for miniaturized slow-light components.
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42.79.Gn Optical waveguides and couplers
68.65.La Quantum wires (patterned in quantum wells)
81.07.Gf Nanowires
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.65.Wi Nonlinear waveguides

Strong exciton-photon coupling in a monolithic ZnO/(Zn,Mg)O multiple quantum well microcavity

S. Halm, S. Kalusniak, S. Sadofev, H.-J. Wünsche, and F. Henneberger

Appl. Phys. Lett. 99, 181121 (2011); http://dx.doi.org/10.1063/1.3657527 (3 pages) | Cited 1 time

Online Publication Date: 3 November 2011

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We report on strong exciton-photon coupling in an epitaxially grown (Zn,Mg)O-based λ-microcavity (MC) containing four 3.5 nm wide ZnO quantum wells (QWs) as active layers. At 5 K, the observed Rabi splitting in absorption is 26 meV, while the inhomogeneous linewidth of A and B excitons in similar QWs without a MC is about 10 meV. The strong coupling regime (SCR) is lost between 150 K and 200 K due to additional homogeneous broadening. From transfer matrix calculations, we deduce that increasing the number of QWs per cavity length can extend the SCR up to room temperature.
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71.35.Gg Exciton-mediated interactions
73.21.Fg Quantum wells
78.67.De Quantum wells

Electrical signal-to-noise ratio improvement in indirect detection of mid-IR signals by wavelength conversion in silicon-on-sapphire waveguides

Y. Huang, E. K. Tien, S. Gao, S. K. Kalyoncu, Q. Song, F. Qian, E. Adas, D. Yildirim, and O. Boyraz

Appl. Phys. Lett. 99, 181122 (2011); http://dx.doi.org/10.1063/1.3651292 (3 pages) | Cited 3 times

Online Publication Date: 3 November 2011

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Planar waveguide devices based on silicon-on-sapphire are emerging as a bridge between mid-infrared (IR) and near-IR wavelength through frequency conversion process. We analyze the limits of indirect detection of mid-IR signals by wavelength conversion in such waveguides and investigate signal-to-noise ratio improvement that is attainable with respect to direct detection using state of the art commercial detectors. Our calculation shows that, in addition to room temperature and high speed operation, the proposed indirect detection can improve the electrical signal-to-noise ratio up to 40 dB compared to direct detection by PbSe, HgCdTe, and InSb detectors, especially in detection of weak mid-IR signals.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

High-Q silica microcavities on a chip: From microtoroid to microsphere

J.-B. Jager, V. Calvo, E. Delamadeleine, E. Hadji, P. Noé, T. Ricart, D. Bucci, and A. Morand

Appl. Phys. Lett. 99, 181123 (2011); http://dx.doi.org/10.1063/1.3658389 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2011

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We report on the realization of high-quality silica optical microcavities on a chip. We show that a precise control of radii of both silica disk and silicon pillar defines the shape of molten microresonators from microtoroids to microspheres. These last ones advantageously combine small mode volumes in structures of very small radii (5 < r < 14 μm) which are fully compatible to wafer-based processing. The optical quality-factor of silica microsphere on a chip is as high as 7.5 × 107 at 1.55 μm. The losses sources in these microspheres are detailed and we show that measured quality-factors are limited by the radiative losses for the smallest ones.
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42.79.-e Optical elements, devices, and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

Simultaneous second-harmonic generation, third-harmonic generation, and four-wave mixing microscopy with single sub-8 fs laser pulses

R. Selm, G. Krauss, A. Leitenstorfer, and A. Zumbusch

Appl. Phys. Lett. 99, 181124 (2011); http://dx.doi.org/10.1063/1.3658456 (3 pages) | Cited 3 times

Online Publication Date: 4 November 2011

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We demonstrate a compact pulse compression scheme that offers flexible chirp control for improved conversion efficiencies in high resolution nonlinear optical microscopy. An Er:fiber laser combined with a highly nonlinear optical fiber yields pulses centered at 1100 nm with a bandwidth of 500 nm. The compressed pulses with a duration of 7.6 fs enable simultaneous second-harmonic generation, third-harmonic generation, and four-wave mixing microscopy. The spectrum is tailored for an ideal compromise between conversion efficiency and spectral discrimination between the three types of broadband nonlinear signals. Distinct differences in structural contrast obtained from the simultaneous read-out of the three nonlinear signals are demonstrated in a biological sample.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
87.64.M- Optical microscopy
42.55.Wd Fiber lasers
42.60.Fc Modulation, tuning, and mode locking
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Increased photoluminescence of strain-reduced, high-Sn composition Ge1−xSnx alloys grown by molecular beam epitaxy

Robert Chen, Hai Lin, Yijie Huo, Charles Hitzman, Theodore I. Kamins, and James S. Harris

Appl. Phys. Lett. 99, 181125 (2011); http://dx.doi.org/10.1063/1.3658632 (3 pages) | Cited 13 times

Online Publication Date: 4 November 2011

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We synthesized up to Ge0.914Sn0.086 alloys on (100) GaAs/InyGa1−yAs buffer layers using molecular beam epitaxy. The buffer layers enable engineered control of strain in the Ge1−xSnx layers to reduce strain-related defects and precipitation. Samples grown under similar conditions show a monotonic increase in the integrated photoluminescence (PL) intensity as the Sn composition is increased, indicating changes in the bandstructure favorable for optoelectronics. We account for bandgap changes from strain and composition to determine a direct bandgap bowing parameter of b = 2.1 ± 0.1. According to our models, these are the first Ge1−xSnx samples that are both direct-bandgap and exhibit PL.
Show PACS
78.55.Hx Other solid inorganic materials
78.66.Bz Metals and metallic alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.30.Mh Solid-phase precipitation
71.20.Lp Intermetallic compounds
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