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18 Oct 2004

Volume 85, Issue 16, pp. 3343-3639

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 3570 (2004); http://dx.doi.org/10.1063/1.1807953 (2 pages)

X. N. Zhang, C. R. Li, Z. Zhang, and Z. X. Cao
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Efficient Raman amplification in silicon-on-insulator waveguides

T. K. Liang and H. K. Tsang

Appl. Phys. Lett. 85, 3343 (2004); http://dx.doi.org/10.1063/1.1807960 (3 pages) | Cited 42 times

Online Publication Date: 22 October 2004

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We describe a silicon-on-insulator waveguide Raman amplifier which achieves a large fiber-to-fiber optical gain of 6.8 dB using stimulated Raman scattering in a 1.7-cm-long silicon waveguide. By using picosecond pulse pumping at 1557.4 nm wavelength, high net optical gain at the first-order Stokes wavelength of 1694.6 nm was measured. The optical loss from two-photon absorption generated free carriers was reduced by using a low pulse duty cycle and picosecond pulse pumping.
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42.55.Wd Fiber lasers
42.55.Px Semiconductor lasers; laser diodes
42.81.Dp Propagation, scattering, and losses; solitons
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
78.30.Am Elemental semiconductors and insulators

High-Q ring resonators in thin silicon-on-insulator

Tom Baehr-Jones, Michael Hochberg, Chris Walker, and Axel Scherer

Appl. Phys. Lett. 85, 3346 (2004); http://dx.doi.org/10.1063/1.1781355 (2 pages) | Cited 21 times

Online Publication Date: 22 October 2004

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We have fabricated high-Q microrings from thin silicon-on-insulater SOI layers and measured Q values of 45 000 in these rings, which were then improved to 57 000 by adding a PMMA cladding. The optimal waveguide designs were calculated, and the waveguide losses were analyzed. These high-Q resonators are expected to lead to interesting devices for telecommunication filters and sources as well as optical refractive index sensing.
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42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Ultrafast-pulse diagnostic using third-order frequency-resolved optical gating in organic films

G. Ramos-Ortiz, M. Cha, S. Thayumanavan, J. Mendez, S. R. Marder, and B. Kippelen

Appl. Phys. Lett. 85, 3348 (2004); http://dx.doi.org/10.1063/1.1807952 (3 pages) | Cited 7 times

Online Publication Date: 22 October 2004

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We report on the diagnostic of ultrafast pulses by frequency-resolved optical gating (FROG) based on strong third-harmonic generation (THG) in amorphous organic thin films. The high THG conversion efficiency of these films allows for the characterization of sub-nanojoule short pulses emitting at telecommunication wavelengths using a low cost portable fiber spectrometer.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Experimental verification of cross talk reduction in photonic crystal waveguide crossings

Young-Geun Roh, Sungjoon Yoon, Heonsu Jeon, Seung-Ho Han, and Q-Han Park

Appl. Phys. Lett. 85, 3351 (2004); http://dx.doi.org/10.1063/1.1808224 (3 pages) | Cited 8 times

Online Publication Date: 22 October 2004

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We have experimentally demonstrated a very low cross talk in photonic crystal waveguide crossings of any kind. For cross talk reduction, we added a resonant cavity to the waveguide intersection designed to operate in microwave frequencies. The two-dimensional waveguide crossing structure was sandwiched between two parallel metal plates to eliminate radiation loss in the vertical direction. Transmission measurements revealed that when designed properly the cross talk reduction was as large as −30 dB at resonance, which is qualitatively consistent with simulation results. From the experimental results, the detailed resonant mode shape at the waveguide intersection was found to play a key role in relaying the input signal in the forward direction and therefore reducing cross talk.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials
42.25.Hz Interference

Dual-frequency addressed hybrid-aligned nematic liquid crystal

Yan-Qing Lu, Xiao Liang, Yung-Hsun Wu, Fang Du, and Shin-Tson Wu

Appl. Phys. Lett. 85, 3354 (2004); http://dx.doi.org/10.1063/1.1809282 (3 pages) | Cited 19 times

Online Publication Date: 22 October 2004

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Dual-frequency addressed hybrid-aligned nematic (HAN) liquid crystal cell is demonstrated as a variable optical attenuator at 1.55 μm wavelength. By controlling the low- and high-frequency electric field, the dual-frequency liquid crystal (DFLC) molecules can be reoriented parallel or perpendicular to the substrates so that the maximum obtainable phase modulation is doubled. In comparison to a homogeneous cell, the DFLC HAN cell shows a lower operating voltage and faster response time. Furthermore, the DFLC HAN cell exhibits three stable states that have some applications such as ternary photonic devices.
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42.70.Df Liquid crystals
42.79.Kr Display devices, liquid-crystal devices
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures

Efficient single-layer “twistacene”-doped polymer white light-emitting diodes

Qianfei Xu, Hieu M. Duong, Fred Wudl, and Yang Yang

Appl. Phys. Lett. 85, 3357 (2004); http://dx.doi.org/10.1063/1.1808250 (3 pages) | Cited 71 times

Online Publication Date: 22 October 2004

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Bright, efficient, and stable white polymer light-emitting diodes based on blue polyfluorene doped by a “twistacene,” 6, 8, 15, 17-tetraphenyl-1.18, 4.5, 9.10, 13.14-tetrabenzoheptacene (3) (TBH), are demonstrated. In “twistacene” the terminal pyrene moieties serve two functions: (i) to stabilize the inherently unstable heptacene and (ii) to enable the oligoacene to be a strongly fluorescent molecule. As a result, efficient and very bright white polymer light-emitting diodes are obtained. The maximum luminance of the devices exceeds 20 000 cd∕m2. The maximum luminous efficiency is 3.55 cd∕A at 4228 cd∕m2 while the maximum power efficiency is 1.6 lm∕W at 310 cd∕m2. The device obtains a stable white balance by a combination of energy transfer from the blue polyfluorene to TBH by 1% TBH doping plus the host emission. The device emission color is not a function of bias current, which is ideal for various applications, from lighting to the backlight for liquid crystal displays.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds

Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: Approaching the near infrared

C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer

Appl. Phys. Lett. 85, 3360 (2004); http://dx.doi.org/10.1063/1.1808232 (3 pages) | Cited 60 times

Online Publication Date: 22 October 2004

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Field-resolved detection of ultrabroadband infrared pulses is implemented with GaSe crystals. Via phase matching, we extend the detectable frequency range toward the near infrared (λ=2.5 μm) and directly record transform-limited pulses as short as 28 fs with a 3 dB bandwidth of 41 THz. The continuous tunability of the center frequency over a wide interval ranging from 31 THz to the far-infrared is demonstrated using thick sensors.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Pw Imaging detectors and sensors
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Optical properties of erbium-implanted porous silicon microcavities

P. J. Reece, M. Gal, H. H. Tan, and C. Jagadish

Appl. Phys. Lett. 85, 3363 (2004); http://dx.doi.org/10.1063/1.1808235 (3 pages) | Cited 10 times

Online Publication Date: 22 October 2004

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We have used ion implantation for erbium doping of mesoporous silicon microcavities. Optically active erbium-doped microcavities with Q factors in excess of 1500 have been demonstrated. We observed strong modification of the emission properties of the erbium in the microcavity with an accompanying cavity enhancement factor of 25. In addition, power- and temperature-dependent photoluminescence measurements indicate that erbium-implanted porous silicon has excitation mechanism very similar to that of erbium in a crystalline silicon host.
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78.66.Db Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
78.55.Mb Porous materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uf Ge and Si

Mid-infrared absorption spectroscopy across a 14.4 THz spectral range using a broadband femtosecond optical parametric oscillator

K. A. Tillman, R. R. J. Maier, D. T. Reid, and E. D. McNaghten

Appl. Phys. Lett. 85, 3366 (2004); http://dx.doi.org/10.1063/1.1808239 (3 pages) | Cited 11 times

Online Publication Date: 22 October 2004

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We describe the implementation of optical absorption spectroscopy in which a Ti:sapphire pumped femtosecond optical parametric oscillator based on periodically poled lithium niobate was used as a broadband source to directly acquire a midinfrared absorption spectrum of methane gas. Fourier-transform spectroscopy was performed using the idler output from the optical parametric oscillator to directly acquire spectra spanning over 600 nm (14.4 THz or 480 cm−1) with around 3 nm (78 GHz or 2.6 cm−1) resolution. This approach combines the advantages of spectroscopy using broadband thermal sources with the high power and excellent beam quality of a mode-locked laser source.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
51.70.+f Optical and dielectric properties

High-contrast modulation of light with light by control of surface plasmon polariton wave coupling

A. V. Krasavin, K. F. MacDonald, N. I. Zheludev, and A. V. Zayats

Appl. Phys. Lett. 85, 3369 (2004); http://dx.doi.org/10.1063/1.1808240 (3 pages) | Cited 32 times

Online Publication Date: 22 October 2004

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We have demonstrated a mechanism for modulating light with light by controlling the efficiency with which light is coupled into a plasmon polariton wave. An optical fluence of 15 mJ∕cm2 in the control channel is sufficient to achieve nearly a ten-fold intensity modulation of the signal beam reflected from a Glass ∕MgF2∕Ga structure. The mechanism depends on a nanoscale light-induced structural transformation in the gallium layer and has transient switching times of the order of a few tens of nanoseconds. It offers high modulation contrast for signals in the visible and near infrared spectral ranges.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Generation and propagation of surface plasmons in periodic metallic structures

G. Torosyan, C. Rau, B. Pradarutti, and R. Beigang

Appl. Phys. Lett. 85, 3372 (2004); http://dx.doi.org/10.1063/1.1806280 (3 pages) | Cited 25 times

Online Publication Date: 22 October 2004

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The generation and propagation of surface plasmon polaritons in periodic metallic structures using femtosecond terahertz pulses is reported. The transmission and emission properties clearly show the influence of Wood’s anomalies. The velocity of propagation is determined experimentally and is in good agreement with a simple model.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Temperature-dependent photovoltaic effects in the manganite-based heterojunction

J. R. Sun, B. G. Shen, Z. G. Sheng, and Y. P. Sun

Appl. Phys. Lett. 85, 3375 (2004); http://dx.doi.org/10.1063/1.1806560 (3 pages) | Cited 32 times

Online Publication Date: 22 October 2004

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Strong temperature-dependent photovoltaic effects have been observed in the heterojunction composed of a La0.32Pr0.35Ca0.33MnO3 (LPCM) film and a 0.5 wt % Nb-doped SrTiO3 substrate. The photovoltage shows a monotonic increase with the decrease of temperature, and its relative change can be as large as ∼7000% for a modest light intensity of 20 mW (wavelength=632 nm) when cooled from room temperature down to 17 K. The synchronous variation of photovoltage and the magnetization of LPCM indicates the magnetic origin of the temperature dependence of the photovoltaic effect. It is suggested that the temperature affects the photovoltaic effect by modifying the magnetic order, then the band structure of LPCM. An enhancement of the photovoltaic effect under strong light illumination is also observed, which is probably a result of illumination-induced change of the band structure of LPCM.
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73.50.Pz Photoconduction and photovoltaic effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.20.Nr Semiconductor compounds

Laser emission from a dye-doped cholesteric liquid crystal pumped by another cholesteric liquid crystal laser

Andro Chanishvili, Guram Chilaya, Gia Petriashvili, Riccardo Barberi, Roberto Bartolino, Gabriella Cipparrone, and Alfredo Mazzulla

Appl. Phys. Lett. 85, 3378 (2004); http://dx.doi.org/10.1063/1.1806561 (3 pages) | Cited 13 times

Online Publication Date: 22 October 2004

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We report the observation of laser emission from a luminescent dye-doped cholesteric liquid crystal (CLC) excited by another dye-doped CLC laser. The idea is based on the cascade of two CLC cells containing two different dyes where the emission band of the first overlaps the absorption band of the second. This system of low threshold mirrorless lasers emphasizes the main advantages of these organic materials for lasing applications and identifies a simple laser device. Preliminary characterizations of these CLC laser systems produce evidence of remarkable features that suggest fascinating developments. The main aspects are related to the wavelength tunability of the laser emission and to the miniaturization of the device.
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42.55.Mv Dye lasers
42.70.Df Liquid crystals
42.79.Kr Display devices, liquid-crystal devices
42.60.Fc Modulation, tuning, and mode locking
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
78.55.Bq Liquids

Prism coupling to on-chip silicon based bragg cladding waveguide

Yasha Yi, Jessica G. Sandland, Shoji Akiyama, Xiaoman Duan, and Lionel C. Kimerling

Appl. Phys. Lett. 85, 3381 (2004); http://dx.doi.org/10.1063/1.1806562 (3 pages) | Cited 3 times

Online Publication Date: 22 October 2004

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We developed a silicon based asymmetric Bragg cladding waveguide, which is composed of high index contrast Si and Si3N4 clad layers and has omnidirectional reflectivity. Prism coupling was used to demonstrate the guiding mechanism by Bragg reflection. The effective index of the propagation mode was measured directly. The measured effective mode index is less than either the Si or Si3N4 cladding layers, which is a clear demonstration of the Bragg waveguiding principle. Low loss of the Si Bragg cladding waveguide around 0.5 dB∕cm for both TE and TM polarizations is achieved. Potential applications include high power transmission, low dispersion, thin cladding thickness, and nonlinear properties engineering on silicon chip.
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42.79.Gn Optical waveguides and couplers
78.30.Hv Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Parametric fluorescence based on the third-order susceptibility χ(3) in high nonlinearity fiber

Yi Ni, Qing Wang, Xiaoming Liu, Jiangde Peng, and Bingkun Zhou

Appl. Phys. Lett. 85, 3384 (2004); http://dx.doi.org/10.1063/1.1808506 (3 pages) | Cited 2 times

Online Publication Date: 22 October 2004

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Parametric fluorescence based on the third-order susceptibility χ(3) in high nonlinearity fiber (HNLF) is quantitatively analyzed by the semiclassical method. In an all-fiber setup consisting of 1.45 km HNLF with nonlinear coefficient γ=12 W−1 km−1, parametric fluorescence power of 360 nW and conversion efficiency as high as 6×10−6 W∕W has been measured with pump power of 57 mW. The measured parametric fluorescence spectrum has good symmetry.
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42.81.Dp Propagation, scattering, and losses; solitons
42.65.An Optical susceptibility, hyperpolarizability

Efficient ultraviolet electroluminescence from a Gd-implanted silicon metal–oxide–semiconductor device

J. M. Sun, W. Skorupa, T. Dekorsy, M. Helm, L. Rebohle, and T. Gebel

Appl. Phys. Lett. 85, 3387 (2004); http://dx.doi.org/10.1063/1.1808488 (3 pages) | Cited 24 times

Online Publication Date: 22 October 2004

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Strong ultraviolet electroluminescence with an external quantum efficiency above 1% is observed from an indium-tin oxide/SiO2:Gd∕Si metal–oxide–semiconductor structure. The SiO2:Gd active layer is prepared by thermal oxidation followed by Gd+ implantation and annealing. The electroluminescence spectra show a sharp peak at 316 nm from the 6P7∕2 to 8S7∕2 transition of Gd3+ ions. Micrometer-sized electroluminescent devices are demonstrated.
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85.60.Jb Light-emitting devices
85.30.Tv Field effect devices
78.60.Fi Electroluminescence
61.72.Cc Kinetics of defect formation and annealing
81.65.Mq Oxidation
78.55.Ap Elemental semiconductors
61.72.up Other materials

Kerr nonlinear effects in AlGaAs multimode waveguides

Marco A. Magaña-Cervantes, Richard M. De La Rue, Daniele Modotto, Costantino De Angelis, Roberto Morandotti, Stefan Linden, Jessica P. Mondia, Henry M. van Driel, and J. Stewart Aitchison

Appl. Phys. Lett. 85, 3390 (2004); http://dx.doi.org/10.1063/1.1807025 (3 pages) | Cited 1 time

Online Publication Date: 22 October 2004

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We have experimentally investigated the linear and nonlinear characteristics of AlGaAs multimode waveguides. By varying the angle of incidence and∕or the intensity of the input beam, it is possible to change the multipeak intensity distributions at the output facet in a controllable fashion. Numerical simulations have reproduced the main features of the intensity profiles observed at the waveguide output over a range of intensities and angles.
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42.79.Gn Optical waveguides and couplers
42.65.Wi Nonlinear waveguides
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
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