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9 Apr 2007

Volume 90, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 151106 (2007); http://dx.doi.org/10.1063/1.2722564 (3 pages)

P. Béjot, L. Bonacina, J. Extermann, M. Moret, J. P. Wolf, R. Ackermann, N. Lascoux, R. Salamé, E. Salmon, J. Kasparian, L. Bergé, S. Champeaux, C. Guet, N. Blanchot, O. Bonville, et al.
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Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition

Jae-Hwang Lee, Wai Leung, Jinho Ahn, Taeho Lee, In-Sung Park, Kristen Constant, and Kai-Ming Ho

Appl. Phys. Lett. 90, 151101 (2007); http://dx.doi.org/10.1063/1.2720752 (3 pages) | Cited 7 times

Online Publication Date: 9 April 2007

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Layer-by-layer three-dimensional photonic crystals are fabricated by low-temperature atomic layer deposition of titanium dioxide on a polymer template created by soft lithography. With a highly conformal layer of titanium dioxide, a significantly enhanced photonic band gap effect appears at 3.1 μm in transmittance and reflectance. From optical investigations of systematically shifted structures, the robust nature of the photonic band gap with respect to structural fluctuations is confirmed experimentally. With angle-resolved Fourier-transform spectroscopy, the authors also demonstrate that the fabricated photonic crystal can be a diffraction-free device as the photonic band gap exists over the diffracting regime.
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42.70.Qs Photonic bandgap materials

Dynamics of quantum dot photonic crystal lasers

Bryan Ellis, Ilya Fushman, Dirk Englund, Bingyang Zhang, Yoshihisa Yamamoto, and Jelena Vučković

Appl. Phys. Lett. 90, 151102 (2007); http://dx.doi.org/10.1063/1.2720753 (3 pages) | Cited 15 times

Online Publication Date: 9 April 2007

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Quantum dot photonic crystal membrane lasers were fabricated and the large-signal modulation characteristics were studied. The authors find that the modulation characteristics of quantum dot lasers can be significantly improved using cavities with large spontaneous emission coupling factor. Their experiments show, and simulations confirm, that the modulation rate is limited by the rate of carrier capture into the dots to around 30 GHz in their present system.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.70.Qs Photonic bandgap materials

Suitability of lithium doped electron injection layers for organic semiconductor lasers

T. Rabe, S. Hamwi, J. Meyer, P. Görrn, T. Riedl, H.-H. Johannes, and W. Kowalsky

Appl. Phys. Lett. 90, 151103 (2007); http://dx.doi.org/10.1063/1.2720757 (3 pages) | Cited 10 times

Online Publication Date: 9 April 2007

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Lithium doped 2,2′,2″-(1,3,5-benzenetryl)tris(1-phenyl)-1H-benzimidazol (TPBi) as electron injection layer in organic laser diodes is investigated. The optical material absorption of optimum doped Li:TPBi is as low as 300 cm−1 at λ = 600 nm. Kelvin probe analysis demonstrates that thin layers (5 nm) of Li:TPBi already enable efficient electron injection from low optical loss transparent conducting oxide contacts. Moreover, stable current densities of about 100 A/cm2 can be injected. The waveguide losses added due to these Li:TPBi layers can be as low as 3 cm−1. These results present a major step towards electrically contacted, low-loss organic laser structures.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.66.Qn Polymers; organic compounds
78.40.Fy Semiconductors
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Electron nanodiffraction using sharply focused parallel probes

Christian Dwyer, Angus I. Kirkland, Peter Hartel, Heiko Müller, and Maximilian Haider

Appl. Phys. Lett. 90, 151104 (2007); http://dx.doi.org/10.1063/1.2721120 (3 pages) | Cited 11 times

Online Publication Date: 9 April 2007

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The authors describe an electron-optical configuration for producing a nanometer-scale sharply focused parallel electron probe in the transmission electron microscope. The configuration utilizes one of the round lenses in an objective prefield aberration corrector and generates a sharply focused parallel probe of 10 nm in diameter, with better than 0.2 nm edge acuity. Such a probe makes it possible to obtain electron diffraction patterns from nanometer-scale volumes of the specimen with unprecedented precision. A method for measuring the transverse coherence of the probe is also described.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.85.Gy Chromatic and geometrical aberrations
41.85.Ne Electrostatic lenses, septa

InGaAs/AlAsSb/InP strain compensated quantum cascade lasers

D. G. Revin, J. W. Cockburn, M. J. Steer, R. J. Airey, M. Hopkinson, A. B. Krysa, L. R. Wilson, and S. Menzel

Appl. Phys. Lett. 90, 151105 (2007); http://dx.doi.org/10.1063/1.2721125 (3 pages) | Cited 9 times

Online Publication Date: 9 April 2007

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The authors demonstrate the feasibility of strain compensated InGaAs/AlAsSb/InP quantum cascade lasers (QCLs). Three QCL structures have been investigated, having identical design but with different indium fractions in InxGa1−xAs quantum wells: 0.53 (lattice matched reference device), 0.6, and 0.7. All lasers display similar operating characteristics at λ ≈ 4.1 μm with no degradation of performance for the strain compensated devices. This strain compensated system is of interest for QCLs at λ< ∼ 3.5 μm. It provides increased energy separation between the Γ and X conduction band minima in the quantum wells, thus decreasing carrier leakage from the upper laser levels by intervalley scattering.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

32 TW atmospheric white-light laser

P. Béjot, L. Bonacina, J. Extermann, M. Moret, J. P. Wolf, R. Ackermann, N. Lascoux, R. Salamé, E. Salmon, J. Kasparian, L. Bergé, S. Champeaux, C. Guet, N. Blanchot, O. Bonville, et al.

Appl. Phys. Lett. 90, 151106 (2007); http://dx.doi.org/10.1063/1.2722564 (3 pages) | Cited 9 times

Online Publication Date: 10 April 2007

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Ultrahigh power laser pulses delivered by the Alisé beamline (26 J, 32 TW pulses) have been sent vertically into the atmosphere. The highly nonlinear propagation of the beam in the air gives rise to more than 400 self-guided filaments. This extremely powerful bundle of laser filaments generates a supercontinuum propagating up to the stratosphere, beyond 20 km. This constitutes the highest power “atmospheric white-light laser” to date.
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42.68.Ay Propagation, transmission, attenuation, and radiative transfer
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

All-optical switching of continuous wave, microsecond lasers with a dye-doped nematic liquid crystal

I. C. Khoo, Jae-Hong Park, and Justin Liou

Appl. Phys. Lett. 90, 151107 (2007); http://dx.doi.org/10.1063/1.2721361 (3 pages) | Cited 10 times

Online Publication Date: 10 April 2007

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The authors present a theoretical analysis and experimental demonstration of optically self-activated polarization switching process in a 90° twist alignment dye-doped nematic liquid crystal. The underlying mechanisms are laser induced dye-assisted director axis reorientation and order parameter modifications. Experimental observations are in good agreement with the theoretical expectations derived from a modified Jones matrix calculation, and demonstrate the feasibility of designing efficient low threshold polarization and fast switching and optical limiting devices for cw and microsecond lasers.
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42.55.-f Lasers
42.70.Hj Laser materials
42.70.Df Liquid crystals
61.30.-v Liquid crystals
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Thermally stable luminescence of KSrPO4:Eu2+ phosphor for white light UV light-emitting diodes

Yu-Sheng Tang, Shu-Fen Hu, Chun Che Lin, Nitin C. Bagkar, and Ru-Shi Liu

Appl. Phys. Lett. 90, 151108 (2007); http://dx.doi.org/10.1063/1.2721846 (3 pages) | Cited 93 times

Online Publication Date: 10 April 2007

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A novel blue phosphor based on phosphate host matrix, KSrPO4 doped with Eu2+, was prepared by solid state reaction. The phosphor invariably emits blue luminescence with a peak wavelength at 424 nm under ultraviolet excitation at 360 nm. Eu2+-doped KSrPO4 phosphors show higher thermally stable luminescence which was found to be better than commercially available Y3Al5O12:Ce3+ phosphor at temperature higher than 225 °C.
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78.55.Hx Other solid inorganic materials
42.70.-a Optical materials
42.72.Bj Visible and ultraviolet sources

Development of green, yellow, and amber light emitting diodes using InGaN multiple quantum well structures

Philip T. Barletta, E. Acar Berkman, Baxter F. Moody, Nadia A. El-Masry, Ahmed M. Emara, Mason J. Reed, and S. M. Bedair

Appl. Phys. Lett. 90, 151109 (2007); http://dx.doi.org/10.1063/1.2721133 (3 pages) | Cited 12 times

Online Publication Date: 11 April 2007

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The authors present optical and electrical data for long wavelength (573–601 nm) InGaN/GaN multiple quantum well light emitting diodes (LEDs) grown by metal organic chemical vapor deposition. These results are achieved by optimizing the active layer growth temperature and the quantum well width. Also, the p-GaN is grown at low temperature to avoid the disintegration of the InGaN quantum wells with high InN content. A redshift is observed for both the green and yellow LEDs upon decreasing the injection current at low current regime. In the case of the yellow LED, this shift is enough to push emission into the amber (601 nm).
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85.60.Jb Light-emitting devices
85.40.Sz Deposition technology

Phase locking of nanosecond pulses in a passively Q-switched two-element fiber laser array

Fanting Kong, Liping Liu, Charlotte Sanders, Y. C. Chen, and Kotik K. Lee

Appl. Phys. Lett. 90, 151110 (2007); http://dx.doi.org/10.1063/1.2721390 (3 pages) | Cited 9 times

Online Publication Date: 11 April 2007

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Phase locking of Brillouin backscattering Q-switched laser pulses that are much shorter than the round-trip time of the resonators has been demonstrated in a two-element fiber laser array. Despite the stochastic dynamics of nonlinear pulse generation, simultaneous generation and phase locking of short pulses have been achieved by using diffractive coupling and spatial filtering in an external resonator.
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42.55.Wd Fiber lasers
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.79.Ci Filters, zone plates, and polarizers
42.79.Gn Optical waveguides and couplers

Microstructure and recording mechanism of Ge/Au bilayer media for write-once optical disc

T. H. Wu, P. C. Kuo, Yen-Hsiang Fang, Jung-Po Chen, Po-Fu Yen, Tzuan-Ren Jeng, Chih-Yuan Wu, and Der-Ray Huang

Appl. Phys. Lett. 90, 151111 (2007); http://dx.doi.org/10.1063/1.2721844 (3 pages) | Cited 7 times

Online Publication Date: 11 April 2007

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The recording mechanism of Ge/Au bilayer and its dynamic tests for write-once blue laser high density DVD (HD DVD) are investigated. It is found that Ge2Au3 phase is nucleated between amorphous Ge and crystalline Au layer after room temperature deposition. Crystallization of Ge/Au interface layer at 170–190 °C is induced by the nucleated Ge2Au3 sites at the interface, the bilayer structure is further heated to 200–450 °C. After heating above 320 °C, crystallized Ge are segregated at the grain boundary. The dynamic test results show that this Ge/Au bilayer films can be applied to 1×–2× HD DVD-R.
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42.79.Vb Optical storage systems, optical disks

Extraordinarily wide-view and high-transmittance vertically aligned liquid crystal displays

Chi-Huang Lin

Appl. Phys. Lett. 90, 151112 (2007); http://dx.doi.org/10.1063/1.2721873 (3 pages) | Cited 6 times

Online Publication Date: 11 April 2007

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A compensation method that uses uniaxial films is developed for widening the viewing angle of the high-transmittance multidomain vertical-alignment liquid crystal display (MVA-LCD). Based on this design, the high-transmittance MVA-LCD is predicted to have a complete 80° viewing cone for contrast ratio (CR)>100:1. Experimental results indicate that the real high-transmittance MVA-LCD panel has a viewing angle more than the entire 80° viewing cone for CR>30:1. Potential application as a mobile display is emphasized.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems

Temperature-insensitive strain sensor with polarization-maintaining photonic crystal fiber based Sagnac interferometer

Xinyong Dong, H. Y. Tam, and P. Shum

Appl. Phys. Lett. 90, 151113 (2007); http://dx.doi.org/10.1063/1.2722058 (3 pages) | Cited 70 times

Online Publication Date: 11 April 2007

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A fiber-optic strain sensor is demonstrated by using a short length of polarization-maintaining photonic crystal fiber (PM-PCF) as the sensing element inserted in a Sagnac loop interferometer. Spectrum shift in response of strain with a sensitivity of 0.23 pm/με is achieved, and the measurement range, by stretching the PM-PCF only, is up to 32 mε. Due to the ultralow thermal sensitivity of the PM-PCF, the proposed strain sensor is inherently insensitive to temperature, eliminating the requirement for temperature compensation.
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42.81.Pa Sensors, gyros
07.60.Vg Fiber-optic instruments
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Pz Instruments for strain, force, and torque
42.70.Qs Photonic bandgap materials
42.81.Gs Birefringence, polarization
07.60.Ly Interferometers

Top-emitting 230 dots/in. active-matrix polymer light-emitting diode displays on flexible metal foil substrates

Ta-Ko Chuang, Matias Troccoli, Po-Chin Kuo, Abbas Jamshidi-Roudbari, Miltiadis K. Hatalis, Ivan Biaggio, and Apostolos T. Voutsas

Appl. Phys. Lett. 90, 151114 (2007); http://dx.doi.org/10.1063/1.2722059 (3 pages) | Cited 9 times

Online Publication Date: 11 April 2007

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A top-emitting 230 dots/in. monochrome active-matrix polymer light-emitting diode (PLED) display having the VGA format and fabricated on a flexible steel foil utilizing the polycrystalline silicon thin-film transistor (TFT) technology is reported. The pixel circuitry architecture consists of the conventional two TFT circuitries made of two p-channel metal-oxide-semiconductor (PMOS) transistors and one storage capacitor. The average field-effect hole mobility and threshold voltage of the PMOS polysilicon TFTs fabricated on the metal foil are 37(±4) cm2/V s and −1.9(±0.6) V, respectively. The light turn-on voltage of the PLED is 4.0 V.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Jb Light-emitting devices
85.60.Pg Display systems
85.30.Tv Field effect devices

High-power, continuous-operation intersubband laser for wavelengths greater than 10 μm

S. Slivken, A. Evans, W. Zhang, and M. Razeghi

Appl. Phys. Lett. 90, 151115 (2007); http://dx.doi.org/10.1063/1.2722190 (3 pages) | Cited 34 times

Online Publication Date: 11 April 2007

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In this letter, high-power continuous-wave emission (>100 mW) and high temperature operation (358 K) at a wavelength of 10.6 μm is demonstrated using an individual diode laser. This wavelength is advantageous for many medium-power applications previously reserved for the carbon dioxide laser. Improved performance was accomplished using industry-standard InP-based materials and by careful attention to design, growth, and fabrication limitations specific to long-wave infrared semiconductor lasers. The main problem areas are explored with regard to laser performance, and general steps are outlined to minimize their impact.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Room temperature laser action from multiple bands in photoexcited GaN grown on a silicon substrate

F. S. Al-Ajmi, R. M. Kolbas, J. C. Roberts, P. Rajagopal, J. W. Cook, Jr., E. L. Piner, and K. J. Linthicum

Appl. Phys. Lett. 90, 151116 (2007); http://dx.doi.org/10.1063/1.2722201 (3 pages) | Cited 1 time

Online Publication Date: 11 April 2007

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Room temperature stimulated emission and laser action with well developed longitudinal optical modes from high-quality GaN films grown on silicon substrates by metal-organic chemical-vapor deposition are presented. Laser action with well developed Fabry-Pérot modes involving the A, B, and C bands was observed. Stimulated emission one exciton below the A band and the B band and one longitudinal optical phonon below the B band was also observed. The effective index of refraction during laser operation was measured to be 2.9.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Group delay measurements on photonic crystal resonators

T. Sünner, M. Gellner, A. Löffler, M. Kamp, and A. Forchel

Appl. Phys. Lett. 90, 151117 (2007); http://dx.doi.org/10.1063/1.2722223 (3 pages) | Cited 3 times

Online Publication Date: 11 April 2007

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The authors have investigated the group delay of light propagating through photonic crystal resonators fabricated in GaAs membranes. The group delay was measured by detecting the phase shift of a microwave signal which was modulated onto the light. The group delay was found to increase linearly with the quality factor of the resonator. A maximum group delay of 132 ps was observed for a resonator with a quality factor of 82 000.
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42.82.Gw Other integrated-optical elements and systems
42.70.Qs Photonic bandgap materials

Si avalanche photodetectors fabricated in standard complementary metal-oxide-semiconductor process

Hyo-Soon Kang, Myung-Jae Lee, and Woo-Young Choi

Appl. Phys. Lett. 90, 151118 (2007); http://dx.doi.org/10.1063/1.2722028 (3 pages) | Cited 13 times

Online Publication Date: 12 April 2007

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The authors report silicon avalanche photodetectors (APDs) fabricated with 0.18 μm standard complementary metal-oxide-semiconductor (CMOS) process without any process modification or a special substrate. When the bias is above the avalanche breakdown voltage, CMOS-compatible APD (CMOS-APD) exhibits negative photoconductance in photocurrent-voltage relationship and rf peaking in the photodetection frequency response. The reflection coefficient measurement of CMOS-APD indicates that rf peaking is due to resonance caused by appearance of inductive components in avalanche region. The rf-peaking frequency increases with the increasing reverse bias voltage.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Enhancement of Alq3 fluorescence by nanotextured silver films deposited on porous alumina substrates

Ziyao Wang, Zhijian Chen, Zhihao Lan, Xiaofeng Zhai, Weimin Du, and Qihuang Gong

Appl. Phys. Lett. 90, 151119 (2007); http://dx.doi.org/10.1063/1.2722231 (3 pages) | Cited 12 times

Online Publication Date: 12 April 2007

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Enhanced photoluminescence was found in tris-8-hydroxyquinoline aluminum deposited onto nanotextured silver films with porous alumina substrates. The surface-enhanced Raman signals and shortened lifetimes suggested the presence of enhanced local electromagnetic field due to the plasmon resonance of nanotextured silver films. The photoluminescence enhancement was attributed to the increase in absorption and quantum yield. The authors analyzed the increase in quantum yield and found that the highest quantum yield was enhanced by 2.3 times compared with the samples based on flat Ag film with the same thickness. The enhancement of quantum yield has potential applications in electro-optic devices.
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78.30.Jw Organic compounds, polymers
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Kz Solid organic materials
Author Select

“Quill” writing with ultrashort light pulses in transparent materials

Peter G. Kazansky, Weijia Yang, Erica Bricchi, James Bovatsek, Alan Arai, Yasuhiko Shimotsuma, Kiyotaka Miura, and Kazuyuki Hirao

Appl. Phys. Lett. 90, 151120 (2007); http://dx.doi.org/10.1063/1.2722240 (3 pages) | Cited 30 times

Online Publication Date: 12 April 2007

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A remarkable phenomenon in ultrafast laser processing of transparent materials, in particular, silica glass, manifested as a change in material modification by reversing the writing direction is observed. The effect resembles writing with a quill pen and is interpreted in terms of anisotropic trapping of electron plasma by a tilted front of the ultrashort laser pulse along the writing direction.
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42.62.-b Laser applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.Ce Glasses, quartz

Electrically driven integrated photonic crystal nanocavity coupled surface emitting laser

Shih-Chieh Huang, Tsung-Hua Yang, Chien-Ping Lee, and Sheng-Di Lin

Appl. Phys. Lett. 90, 151121 (2007); http://dx.doi.org/10.1063/1.2721372 (3 pages) | Cited 1 time

Online Publication Date: 13 April 2007

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Single mode surface emitting lasers with photonic crystal nanocavities integrated with electrically driven strained quantum well laser diodes are demonstrated. The photonic crystal serves as an end mirror for the laser cavity, while the nanocavities serve as wavelength selective high Q surface emitters. The laser emission from the nanocavities had excellent temperature stability. The wavelength shift versus temperature was about five times better than that of regular quantum well lasers. Dual wavelength emission from two side by side slightly different cavities was also demonstrated. Laser emission with two wavelengths of Δλ = 0.8 nm was obtained.
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42.55.Px Semiconductor lasers; laser diodes
42.70.Qs Photonic bandgap materials
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems
42.82.-m Integrated optics
42.79.Bh Lenses, prisms and mirrors

Phosphor-free white-light light-emitting diode of weakly carrier-density-dependent spectrum with prestrained growth of InGaN/GaN quantum wells

Chi-Feng Huang, Chih-Feng Lu, Tsung-Yi Tang, Jeng-Jie Huang, and C. C. Yang

Appl. Phys. Lett. 90, 151122 (2007); http://dx.doi.org/10.1063/1.2723197 (3 pages) | Cited 26 times

Online Publication Date: 13 April 2007

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The authors grew a white-light InGaN/GaN quantum-well (QW) light-emitting diode epitaxial structure with its electroluminescence spectrum close to the ideal condition in the Commission International de l’Eclairage chromaticity based on the prestrained metal-organic chemical vapor deposition technique. The prestrained growth leads to the efficient yellow emission from three InGaN/GaN QWs of increased indium incorporation. The color mixing for white light is implemented by adding a blue-emitting QW at the top of the yellow-emitting QWs. The blueshifts of the blue and yellow spectral peaks of the generated electroluminescence spectra are only 1.67 and 8 nm, respectively, when the injection current increases from 10 to 70 mA. Such small blueshifts imply that the piezoelectric fields in their QWs are significantly weaker than those previously reported.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Full field phase imaging using a harmonically matched diffraction grating pair based homodyne quadrature interferometer

Jigang Wu, Zahid Yaqoob, Xin Heng, Lap Man Lee, Xiquan Cui, and Changhuei Yang

Appl. Phys. Lett. 90, 151123 (2007); http://dx.doi.org/10.1063/1.2722685 (3 pages) | Cited 3 times

Online Publication Date: 13 April 2007

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In this letter, the authors present a novel quadrature interferometry method based on the use of a harmonically matched shallow grating pair. Unlike a simple beam splitter or single shallow grating, the grating pair can confer a nontrivial interference phase shift (other than 0° or 180°) between the output ports of the interferometer. Using the grating pair as the beam splitter/combiner, the authors implement a homodyne quadrature full field phase interferometer and demonstrate the system’s capability to acquire phase and amplitude images.
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07.60.Ly Interferometers
42.79.Dj Gratings

Fast speed electro-optic polymer variable optical attenuator based on cascaded attenuated-total-reflection technique

Xiaoxu Deng, Xiang Zheng, Zhuangqi Cao, Qishun Shen, and Honggen Li

Appl. Phys. Lett. 90, 151124 (2007); http://dx.doi.org/10.1063/1.2723196 (3 pages) | Cited 3 times

Online Publication Date: 13 April 2007

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A fast speed electro-optic polymer variable optical attenuator (VOA) is fabricated by utilizing cascaded attenuated-total-reflection technique. The proposed VOA demonstrates high dynamic range and low driving voltage. An ∼ 200 ns response time of the device is obtained, and other measured parameters include a dynamic range up to 24.1 dB, a driving voltage of 39.6 V, and an insertion loss of 1.02 dB.
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42.82.Gw Other integrated-optical elements and systems
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

High quality factor microcavity lasers realized by circular photonic crystal with isotropic photonic band gap effect

Po-Tsung Lee, Tsan-Wen Lu, Jyun-Hao Fan, and Feng-Mao Tsai

Appl. Phys. Lett. 90, 151125 (2007); http://dx.doi.org/10.1063/1.2724899 (3 pages) | Cited 15 times

Online Publication Date: 13 April 2007

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The photonic band gap (PBG) effect and its isotropy of sunflower-type circular photonic crystal (CPC) are obtained and investigated from the transmission spectra performed by finite-difference time-domain (FDTD) method. The PBG directional width variation is found to be only 6.7%. A well-confined whispering gallery mode (WGM) with azimuthal number of 6 is obtained by FDTD simulation from the CPC microcavity formed by seven missing air holes (C2). Ascribed to the deep and isotropic PBG confinement, the WGM lasing with very-low threshold ( ∼ 0.13 mW) and very-high-quality (Q) factor (>10 000) is obtained from well-fabricated CPC C2 microcavity lasers.
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42.55.Sa Microcavity and microdisk lasers
42.55.Tv Photonic crystal lasers and coherent effects
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
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