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PhotonicsGlobal@Singapore, 2008. IPGC 2008. IEEE

Date 8-11 Dec. 2008

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Displaying Results 1 - 25 of 222
  • Light Emission and Detection for Si Photonics

    Publication Year: 2008 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3150 KB) |  | HTML iconHTML  

    The present paper reviews the current status of light emission and detection for Si Photonics. To control the initial and final stages, strain engineering of bandgap and resonator structures are indispensable for light emission. A new non-thermal approach to reduce reverse leakage current is proposed controlling the electric field strength. These together with modulation reported recently on Ge platform clearly indicates that Ge is one of the most important materials as far as active components are concerned. View full abstract»

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  • Progress in Silicon Microresonator-Based Passive Devices: Optical Delay Lines, Switch Matrix, and Linear-Absorption-Induced Thermo-Optical Dispersion

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    This invited paper reviews our recent progress in silicon microresonator-based passive devices for potential on-chip optical interconnect applications. Specifically, we report our proposals and initial demonstrations of (i) many-element cascaded microdisk resonators as optical delay lines, and (ii) cascaded microring switch matrix. We also report our study on surface-state absorption-induced thermo-optical dispersion in silicon microresonators. Due to the spatial overlap between the cavity whispering-gallery mode field and the cavity sidewalls and surfaces, we find that the surface-state absorption of cavity optical power in the range of milliwatt is sufficient to cause an undesirable resonance wavelength red-shift in the order of 0.1 nm. View full abstract»

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  • Submicron silicon photonic micro-ring resonator: Polarization independence

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (250 KB) |  | HTML iconHTML  

    There is a recent trend to reduce waveguide based silicon photonic devices to the sub-micron regime for increased chip density and better cost efficiency. However, designing polarization independent (PI) ring resonator using submicron waveguide is a challenge as it exhibits strong polarization dependency. We demonstrate theoretically the feasibility of realizing both single-mode (SM) and PI operation in ring resonator based on sub-micron silicon-on-insulator (SOI) rib waveguides. A resonance spectra misalignment that represents only 11% of the full-width half-maximum (FWHM) linewidth of 1.64 nm is achieved, with a free spectra range of 13 nm. View full abstract»

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  • 50th order series-coupled micro-ring resonator

    Publication Year: 2008 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (630 KB) |  | HTML iconHTML  

    A 50th order series-coupled micro-ring resonator fabricated on silicon-on-insulator is demonstrated for optical filtering applications. The fabricated device is compact and has box-like transmission profile. The measured out-of-band signal rejection ratio is ~65 dB. View full abstract»

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  • Silicon Photonic Crystal Surface Mode Microcavities

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (357 KB) |  | HTML iconHTML  

    High-Q surface mode micro-cavities in silicon-on-insulator (SOI) structures are investigated. Cavity structures in amorphous silicon based SOI structures show intrinsic Q values of 2000, while cavities in crystalline SOI structures can have intrinsic Q values larger than 104. View full abstract»

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  • Silicon Nanophotonic Waveguide and Coupling

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB) |  | HTML iconHTML  

    Modal characterization of silicon nanophotonic waveguide and its coupling to an optical fiber are investigated, which include: 1) a full-vectorial modal analysis of silicon nanophotonic waveguide and a TM-pass nanophotonic polarizer based on a simple taper structure; 2) a superlens based coupling structure between nanophotonic waveguide and singlemode fiber with a designed coupling loss ~0.64 dB and 3) a brief introduction on our cluster computing simulation platform and computational intelligence based optimizations for nanophotonic circuits. View full abstract»

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  • Bistability engineering in ring-coupled Mach-Zehnder interferometers for efficient all-optical switching

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (275 KB) |  | HTML iconHTML  

    We propose a two-ring structure that can generate an ultra-narrow resonance which may be used, together with the Mach-Zehnder interferometer (MZI), to engineer bistability switching with low switching threshold and reasonably high extinction ratio (ER) and modulation depth (MD). The two-ring MZI (2RMZI) is also compared with the conventional one-ring MZI (1RMZI). A flexible optimization scheme has been developed and can be used to obtain maximum ER and MD. Complementary relationship between switching threshold, sensitivity to loss and optical bandwidth are discussed for the two types of devices. View full abstract»

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  • A Resonator-based Silicon Electro-optic Modulator with Ultra-low Power Consumption and Optimized Modulation Performance

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    This paper demonstrates, via simulation, an electro-optic modulator based on a subwavelength Fabry-Perot resonator cavity with ultra-low power consumption. The device is modulated at a doped p-i-n junction overlapping the cavity in a silicon waveguide perforated with etched holes, with the doping area optimized for minimum power consumption. The surface area of the entire device is only 2.1 mum2. Our optical and electrical simulations demonstrate a resonance peak shift of 12 nm with 0.5 mW power consumption. Transient results indicate that the modulation depth exceeds 10 dB at a modulation speed of 100 MHz with the power consumption comparing favorably to a previous report [1]. This speed can be further improved to 250 MHz by using an optimized driving signal [2]. Finally, the etched holes forming the cavity have been tapered [3], [4] to maximize insertion, and the etching depth of those holes is tuned to reduce fabrication complexity. The device does not rely on ultra-high Q, and the huge peak shift detected could be applied to a sensor [5]-[7], modulator, or passive filter with built-in calibration. View full abstract»

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  • Ultra-compact silicon-on-insulator optical filter based on sidewall Bragg grating

    Publication Year: 2008 , Page(s): 1 - 4
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1247 KB) |  | HTML iconHTML  

    Micro-cavity structure composed of silicon wire with 240 nm square cross section and two symmetrical sidewall waveguide Bragg gratings is fabricated and studied for the operation under telecommunication wavelengths. Optical filter of quasi-TE mode was realized based on this cavity. In such micro-cavity, optical quality factor (Q) was measured up to 380 with a 4.8 nm free spectral range (FSR) and 12 dB fringe contrast (FC). The measured group index of silicon waveguide with only 240 nm square cross section was between 3.80 and 5.43. It is the first time group delay of silicon wire waveguide with such small core dimension is studied. Larger group delay can be expected after optimizing the design parameters and the fabrication process. View full abstract»

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  • Nanophotonics Based Cantilever Sensor

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4987 KB) |  | HTML iconHTML  

    We present design and simulation results of a novel nanomechanical sensor using a silicon cantilever comprising two-dimensional (2-D) photonic crystal (PC) microcavity resonator structure. A U-shaped silicon line defect in a 2-D photonic crystal is considered as a waveguide for confining light propagation within waveguide, while two-hole pairs are placed along this silicon waveguide as a optical reflector. The resonant wavelength of output spectrum is sensitive to the shape of air holes and defect length of the microcavity resonator. The minimum detectable strain, vertical deflection at the cantilever end, and force load are observed as 0.0136%, 0.94 mum and 0.046 muN for 50 mum cantilever. The measured strain is a linear function of resonant wavelength shift and applied force. This new sensing shows promising features for biomolecules detection. View full abstract»

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  • Broadband Flat-top Superluminescent Diode with Low Spectral Modulation at 850 nm

    Publication Year: 2008 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    The broadest bandwidth (80 nm) superluminescent diode (SLD) with center wavelength at 850 nm fabricated on GaAs/AlGaAs double quantum-well structure is characterized and analyzed. The broadband flat-top like spectrum and a 0.3 dB spectral modulation enable this device to produce an axial resolution of 4 mum in optical coherence tomography systems. View full abstract»

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  • Far-field patterns of Quantum Well, Quantum Dash, and Quantum Dot Laser Diodes

    Publication Year: 2008 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (423 KB) |  | HTML iconHTML  

    We perform measurements of far field pattern of various quantum-confined heterostructures namely quantum well (QW), quantum dash (Qdash), and quantum dot (Qdot) lasers to study the effect of different active gain mediums of semiconductor lasers on the optical beam quality and coupling efficiency. The beam pattern profile of the Qdash laser is similar to that of the QW laser (FWHM ~ 20deg) while Qdot laser shows smaller divergence (FWHM ~ 5deg) and retain its intensity profile of single lobe Gaussian-shape at current injection up to two and half times threshold current. View full abstract»

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  • Single-lobe operation of a submicron-ridge laser arrays

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (350 KB) |  | HTML iconHTML  

    Strong optical- and electrical-interaction can occur between optoelectronic devices when the element-size and inter-element spacing are significantly reduced. In this study, we investigate these interactions in the closely packed submicron-laser diode arrays. View full abstract»

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  • Effect of Nitrogen on Indium Segregation in GaInNAs/GaAs Quantum Wells

    Publication Year: 2008 , Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB) |  | HTML iconHTML  

    A kinetic model has been developed to study the effect of nitrogen on indium segregation for GaInNAs/GaAs quantum wells. Our results suggest that nitrogen tends to enhance the indium-gallium exchange process. The incorporation of nitrogen is found to increases the segregation length up to a maximum value, which decreases with further increase in nitrogen concentration. View full abstract»

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  • Intermixing of InGaAs/GaAs Quantum Well Using Multiple Cycles Annealing

    Publication Year: 2008 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB) |  | HTML iconHTML  

    The authors investigate the effect of intermixing in shallow InGaAs/GaAs quantum well structure using impurity free induced disordering (IFVD) technique. The degradation of the photoluminescence (PL) signal is due to the severe loss of As from the material during high temperature annealing at above intermixing activation energy. The recovery of the PL signal from the intermixed InGaAs/GaAs quantum-well has been found to be achieved by applying a cycle-annealing at 800degC which is below activation temperature. View full abstract»

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  • Gain and alpha factor of intermixed InAs/InAlGaAs quantum-dash lasers

    Publication Year: 2008 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB) |  | HTML iconHTML  

    We study the optical gain and alpha factor of InAs/InAlGaAs quantum-dash lasers on InP substrate after being subjected to the postgrowth intermixing process. The intermixing was achieved using dielectric capping process that involves the deposition of dielectric film and subsequent rapid thermal annealing. Compared to the un-intermixed laser, we found that the intermixed lasers with a 93 nm bandgap blue-shift exhibit good material quality with improved differential gain and comparable alpha factor. View full abstract»

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  • Nanophotonics for Information Systems Integration

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (754 KB) |  | HTML iconHTML  

    The field of nanophotonics is finding myriad applications in information technology, health care, lighting, sensing and national security. This article explores the role of nanotechnology with special focus on nanophotonics in dielectric and inhomogeneous metamaterials with applications for optical communications, optical signal processing, and sensing. View full abstract»

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  • Nano - ZnO in Photonics Landscape

    Publication Year: 2008 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (7428 KB) |  | HTML iconHTML  

    Methodologies have been evolved to grow optical quality nanostructures of the 3.4 eV band-gap semiconductor ZnO and its doped variants with different orders of dimensionality. These nanostructures are versatile and yet under evolution for next generation UV-blue photonic and spin-photonic devices. There are pending lacunae such as reliable and enduring p-type carrier doping and large carrier mobility etc, which need further and deeper understanding of fundamental nature of ZnO as a semiconductor. View full abstract»

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  • In-N co-doped P-type ZnO films electrical prepared by modified ion beam enhanced deposition

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    In-N co-doped P-type ZnO films were prepared on SiO2 and glass substrates by IBED method. The structural, optical and electrical properties were characterized by XRD, XPS, AFM and Hall test. The tests results show that the film was polycrystalline with a preferred (002) orientation. The resistivity, mobility and carrier concentration was 1.6times10-3 Omegamiddotcm, 35.9 cm2/VmiddotS and 1.66times1020/cm3 after annealing at 600degC for 30 min, respectively. View full abstract»

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  • Patterned ZnO nanowires grown on single layer polystyrene spheres and their application in dye sensitive solar cell

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1417 KB) |  | HTML iconHTML  

    Patterned ZnO nanowires were successfully grown on single layer polystyrene spheres on ITO glass substrate using a low temperature hydrothermal method. Ordered hollow spherical spaces formed between ZnO nanowires layer and the substrate. The patterned ZnO nanowires were used as the photoelectrode of the dye sensitive solar cell (DSSC). The DSSC shows higher open-circuit voltage and short-circuit current as well as better overall efficiency than that of the DSSC based on the ZnO nanowires arrays synthesized under the same condition. The improved performance of the patterned ZnO nanowires DSSC is attributed to the patterned nanowires DSSC architecture, which not only increases the surface area of the photoelectrode, but also depresses the recombination process and increases the light harvesting ability. View full abstract»

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  • Growth of III-Nitride Materials and Blue Light-Emitting Diodes by Metal Organic Vapor Phase Epitaxy

    Publication Year: 2008 , Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (643 KB) |  | HTML iconHTML  

    GaN-based materials and devices are expected to play an important role in future information and energy applications. In this paper, we summarized our recent results in metal organic vapor phase epitaxy growth of nitride materials and blue light-emitting diodes (LEDs) on c-plane sapphire substrates. First, the key parameters for high quality GaN bulk growth have been discussed and an evaluating method for crystal structures based on the high resolution X-ray diffraction (HR-XRD) has been introduced. It is found that the optimal recrystallization time and the growth of high temperature buffer layer using a low V/III ratio are helpful to improve the crystal quality of GaN. Furthermore, in order to determine the twist angle of GaN films precisely, a simple and effective geometrical model is established to distinguish the contributions of tilt and twist to the full width at half maximum of HR-XRD Phi-scan curves. Second, the growth of low In content InGaN templates of 500 nm has been studied. The crystal quality of thick InGaN templates is improved efficiently by inserting a 15 nm low temperature growth InGaN buffer layer, which is attributed to the rapid strain relaxation. Finally, the growth and electrical characteristics of blue InGaN/GaN multiple-quantum-well LEDs are presented. The doping profiles are found to influence the electrical characteristics of LEDs dramatically by capacitance-voltage measurements. View full abstract»

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  • Optimization and Fabrication of III-Nitride Light-Emitting Diodes with Self-assembled Colloidal-based Convex Microlens Arrays

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1019 KB) |  | HTML iconHTML  

    Improvement of light extraction efficiency of InGaN light emitting diodes (LEDs) using colloidal-based SiO2 / polystyrene microlens arrays was demonstrated. The size effect of the SiO2 microspheres and the thickness of the polystyrene layer on the light extraction efficiency were studied. Ray tracing simulations show that the use of microlens arrays leads to increase in light extraction efficiency by 2.6 times. This is consistent with experiments that demonstrated 2.7 times improvement in light extraction utilizing SiO2/polystyrene microlens arrays. The enhancement in light extraction efficiency is attributed to increase in effective photon escape cone due to SiO2/polystyrene microlens arrays. View full abstract»

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  • Optical Properties of Semiconductor Quantum Dots

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3996 KB) |  | HTML iconHTML  

    An important step towards realizing the advantages of quantum dots in electro-optic applications is to understand the excitation dependences of optical properties. This paper discusses results obtained using a microscopic theory. The calculations uncovered complicated carrier density and electronic structure influences on absorption, gain and refractive index that can be attributed to a delicate balancing of electronic-structure and many-body effects in a coupled quantum-dot-quantum-well system. View full abstract»

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  • Bandgap-Engineered Broadband Stimulated Emission in Semiconductor Quantum Dash Interband Laser

    Publication Year: 2008 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    Authors demonstrate the generation of broadband stimulated emission in the postgrowth wavelength tuned InAs/InAlGaAs quantum-dash (Qdash) laser grown on InP substrate. The laser exhibits room temperature lasing wavelength coverage of up to 50 nm at center wavelength of ~1.57 mum. Despite the bandgap blue-shift of ~70 nm after Qdash intermixing process, the laser exhibits a broadband signature of lasing linewidth, which is comparable to the as-grown laser. The integrity of the material is retained after intermixing, suggesting its potential application in the fabrication of monolitically-integrated ultra-broadband semiconductor Qdash laser. View full abstract»

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  • Tuning and Modulation in Two Section Quantum Dot Lasers

    Publication Year: 2008 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    Two section lasers enable some novel properties of quantum dots to be realised. Engineering these quantum dots results in two very different behaviours with associated application areas, shown here are optical coherence tomography and datacomms. View full abstract»

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