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Photonics Technology Letters, IEEE

Issue 23 • Date Dec.1, 2011

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Displaying Results 1 - 25 of 39
  • [Front cover]

    Publication Year: 2011 , Page(s): C1
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    Freely Available from IEEE
  • IEEE Photonics Technology Letters publication information

    Publication Year: 2011 , Page(s): C2
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    Freely Available from IEEE
  • Table of contents

    Publication Year: 2011 , Page(s): 1743 - 1744
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  • Research on Performance of Red Vertical AlGaInP/GaAs Light-Emitting Diodes Influenced by Current Crowding

    Publication Year: 2011 , Page(s): 1745 - 1747
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (473 KB) |  | HTML iconHTML  

    The authors show that the performance of red vertical AlGaInP/GaAs light-emitting diodes is compromised by the current crowding (CC) effect in the moderate-current (space charge region dominates in the device performance) and high-current (series resistance dominates in the equivalent circuit of a device) domains. Depending on the contact pattern, a remarkable part of the performance degradation comes as a result of the electrical power lost on the series resistance (~17%). CC affects the ideality factor and causes the current spreading length to decrease from 425 at low currents to 75 at a current of 250 mA. View full abstract»

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  • High-Speed InAs Quantum-Dot Electrooptic Phase Modulators

    Publication Year: 2011 , Page(s): 1748 - 1750
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    In this letter, we report results of direct current (dc) and radio-frequency (RF) characteristics of self-assembled InAs quantum-dot (QD) electrooptic modulators. Although dc modulation results have been reported in the literature, these are the first high-frequency designs and measurements. These QD modulator wafers were grown by molecular beam epitaxy (MBE) and phase modulator devices were fabricated with coplanar traveling-wave electrodes. For the 800-μm-long modulators, the half-wave voltage Vπ was measured as 11.4 V at 1.55 μm and 7.34 V at 1.32 μm. The phase variation is 21.9°/(mm·V). The linear electrooptic coefficient T41 is calculated to be 35.4 pm/V for QDs. These modulators have a 3-dB bandwidth of 10 GHz. A signal-to-noise ratio of 9 dB was measured at 20 GHz. View full abstract»

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  • Room-Temperature Electroluminescence From GeSn Light-Emitting Pin Diodes on Si

    Publication Year: 2011 , Page(s): 1751 - 1753
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    In this letter, a GeSn light-emitting pin diode integrated on Si via a Ge buffer is demonstrated and it is compared with a light-emitting pin diode made from pure, unstrained Ge on Si. The diode layer structures are grown with a special low-temperature molecular beam epitaxy process. The pseudomorphic GeSn layers (1.1% Sn content) on the Ge buffer are compressively strained. Both light-emitting pin diodes clearly show direct bandgap electroluminescence emission at room temperature. The electroluminescence peak of the GeSn light-emitting pin diode is shifted by 20 meV into the infrared region compared to the electroluminescence peak of the unstrained Ge light-emitting pin diode. The shift is due to the lower bandgap of GeSn and the influence of strain. View full abstract»

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  • Ultra-Wideband Generation Based on Cascaded Mach–Zehnder Modulators

    Publication Year: 2011 , Page(s): 1754 - 1756
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (597 KB) |  | HTML iconHTML  

    A simple approach to generating ultra-wideband (UWB) pulses with a single optical carrier is proposed and demonstrated. The approach is realized by using a single laser diode (LD) and two cascaded Mach-Zehnder modulators (MZMs). In the experiment, the two MZMs are biased at opposite slopes of their modulation curves respectively and the time delay between them is variable. Negative monocycle pulses with a center frequency of 4.3 GHz and a fractional bandwidth of 165%, and positive monocycle pulses with a center frequency of 4.3 GHz and a fractional bandwidth of 188% are generated, respectively. The feasibility of high order UWB pulses generation with a single optical carrier is also discussed. View full abstract»

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  • Emission Efficiency Dependence on the p-GaN Thickness in a High-Indium InGaN/GaN Quantum-Well Light-Emitting Diode

    Publication Year: 2011 , Page(s): 1757 - 1759
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    The dependencies of quantum-well (QW) internal quantum efficiency (IQE) and device behaviors on the p-layer thickness in a high-indium InGaN/GaN QW light-emitting diode (LED) are demonstrated. During the high-temperature growths of the p-AlGaN and p-GaN layers, the QWs are thermally annealed to increase their IQEs and blue-shift the emission with increasing p-layer thickness. Meanwhile, the quantum-confined Stark effect is enhanced with increasing p-layer thickness to decrease the IQEs and red-shift the emission. Based on the counteraction between the two effects, the maximum IQE and the shortest emission wavelength are observed in a sample with an optimized p-layer thickness, which includes a p-AlGaN layer of 20 nm and a p-GaN layer of 60 nm in thickness under our growth conditions. The fabricated LEDs of different p-GaN thicknesses show the similar variation trends in emission efficiency and wavelength. View full abstract»

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  • Heterogeneous Integration of GaInAsSb p-i-n Photodiodes on a Silicon-on-Insulator Waveguide Circuit

    Publication Year: 2011 , Page(s): 1760 - 1762
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    We report the integration of GalnAsSb p-i-n photo diodes on a silicon-on-insulator waveguide circuit. The device operates with low dark current (1.13 μA at -0.1 V) at room temperature. A high responsivity of 0.44 A/W is measured at 2.29 μm. This yields 1.63 × 109 cmHz1/2/W of Johnson-noise-limited-detectivity. View full abstract»

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  • The Multipeak Phenomena and Nonlinear Effects in {Q} -Switched Fiber Lasers

    Publication Year: 2011 , Page(s): 1763 - 1765
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (606 KB) |  | HTML iconHTML  

    We investigate control of the Q-switch rise time as a means to eliminate the undesirable formation of multipeak structure within actively Q-switched fiber lasers. Our experiments show that the development of pulse substructure is solely due to gain dynamic effects and that nonlinearity does not play a decisive role in the process. Using a spectrally resolved optical time gating technique, we investigate nonlinear pulse evolution for both smooth and structured Q-switch pulses of otherwise similar characteristics in Q-switch cavity comprising anomalously dispersive fiber. Useful insight is obtained into the complex interplay of the gain dynamic and various nonlinear effects governing the detailed pulse evolution. The measurements highlight the value and potential of this characterization technique for studying such lasers. View full abstract»

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  • Simplified Design of Multiport Optical Circulator With Parallel Connection of Mirror-Image Arranged Spatial- and Polarization-Modules

    Publication Year: 2011 , Page(s): 1766 - 1768
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (533 KB) |  | HTML iconHTML  

    This letter proposes a simplified design of multiport optical circulator with parallel connection of mirror-image arranged spatial- and polarization-modules. To show the feasibility of the design, a prototype of six-port optical circulator was fabricated. The insertion losses are 0.51-1.05 dB, the isolations are 26.20-45.13 dB, and return losses are 27.72 dB. This design should bear merits of a simple and symmetric structure that is low cost, easily fabricated, polarization-independent, and polarization-mode dispersion resolved, and exhibits high performance. View full abstract»

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  • C -Band Optical 90 ^{\circ} Hybrids in Silicon Nanowaveguide Technology

    Publication Year: 2011 , Page(s): 1769 - 1771
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB) |  | HTML iconHTML  

    We present a fully passive silicon nanowire-based optical 90° hybrid based on a 4 × 4 multimode interference (MMI) coupler for application in coherent receivers. Simulations show 4×4 MMI coupler performance regarding excess loss, imbalance, bandwidth, and phase accuracy. The 4×4 MMI couplers show stable performance over C-band with excess loss and imbalance<; 0.5 dB and phase accuracy better than 5°. We obtain over C-band minimum extinction ratios of 20 dB. View full abstract»

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  • Enhanced Performance of LEDs Using Periodic Tent-Like Post Patterns on A-plane Sapphire Substrates

    Publication Year: 2011 , Page(s): 1772 - 1774
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    Periodic tent-like post patterns on a-plane sapphire substrates were fabricated using a two-step etching process. They were denoted as a-plane dot pattern sapphire substrate (ADPSS). Compared with the GaN-based light-emitting diode (LED) grown on a-plane sapphire without any pattern (AFlat), the ADPSS-LED has higher output power, light extraction efficiency (LEE), and external quantum efficiency (EQE), and better crystal quality. The output power of ADPSS-LED was 9.6 mW, which was 68.4% larger than the AFlat-LED. In addition, the blue shift of ADPSS-LED was found to be less than that of AFlat-LED. View full abstract»

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  • Widely Tunable Single-Passband Microwave Photonic Filter Based on Stimulated Brillouin Scattering

    Publication Year: 2011 , Page(s): 1775 - 1777
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (507 KB) |  | HTML iconHTML  

    A new ultrawide continuously tunable single-passband microwave photonic filter with very high resolution, is presented. It is based on a stimulated Brillouin scattering technique using a phase modulated optical signal and a dual-sideband suppressed-carrier pump. Results are presented which demonstrate a 1- to 20-GHz measured tuning range, together with continuous tuning, extremely high resolution with a -3-dB bandwidth of only 20 MHz, a single passband, shape-invariant tuning, and a high out-of-band rejection of 31 dB. View full abstract»

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  • A Method for Exact Synthesis of 2\times N Coupled Microring Resonator Networks

    Publication Year: 2011 , Page(s): 1778 - 1780
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (899 KB) |  | HTML iconHTML  

    We present a simple method for synthesizing coupled microring resonator networks having a 2 × N coupling topology. The method is based on the field coupling formalism of 2-D coupled microrings and is applicable for designing broadband filters in the z-domain. View full abstract»

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  • 1310-nm Hybrid III–V/Si Fabry–Pérot Laser Based on Adhesive Bonding

    Publication Year: 2011 , Page(s): 1781 - 1783
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB) |  | HTML iconHTML  

    An evanescently coupled, hybrid III-V/Silicon Fabry-Pérot laser based on adhesive divinyl siloxane-benzocyclobutene (DVS-BCB) bonding is presented operating at 1310 nm. We obtain 5.2-mW output power in continuous-wave (CW) regime at 10 °C with a threshold current density of 2.83 kA/cm2 in an 800-μm -long device. A specially developed bonding procedure produces 50-nm-thick bonding layers, enabling the evanescent coupling. View full abstract»

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  • Highly Reliable Ohmic Contacts to N-Polar n-Type GaN for High-Power Vertical Light-Emitting Diodes

    Publication Year: 2011 , Page(s): 1784 - 1786
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (589 KB) |  | HTML iconHTML  

    We report on the formation of highly reliable Ti/Al-based Ohmic contacts to N-polar n-GaN for vertical light-emitting diodes via laser-annealing. All as-deposited samples are Ohmic with specific contact resistances of 1.1 - 4.3 × 10-4 Ω cm2. After annealing at 250°C, unlike the untreated sample, the laser-annealed samples remain Ohmic with specific contact resistances of 2.6- 3.9 × 10-4 Ω cm2. The laser-annealed samples remain electrically stable up to 60 min at 300°C. Laser-annealing causes the formation of interfacial TiN/β -AlN phases with rock salt structure. Based on X-ray photoemission spectroscopy and scanning transmission electron microscopy results, possible Ohmic mechanisms are described. View full abstract»

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  • Uniform Polarization-Dispersion Compensation of All Channels in Highly Birefringent Silicon Nanowire-Based Arrayed Waveguide Grating

    Publication Year: 2011 , Page(s): 1787 - 1789
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB) |  | HTML iconHTML  

    A design method for compensating polarization dispersion in arrayed waveguide gratings (AWGs) based on highly birefringent silicon nanowire waveguides is proposed by using angled star couplers in combination with different diffraction orders for TE and TM polarizations. Polarization-dispersion compensation for all output channels is achieved with the maximal polarization-dependent wavelength shift of 0.025 nm in an eight-channel AWG with 200-GHz spacing using 380 nm × 220 nm silicon waveguide with SU-8 upper-cladding. View full abstract»

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  • Self-Assembled Graphene Membrane as an Ultrafast Mode-Locker in an Erbium Fiber Laser

    Publication Year: 2011 , Page(s): 1790 - 1792
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB) |  | HTML iconHTML  

    A self-assembled graphene membrane produced at the liquid/air interface of reduced graphene oxide aqueous suspension is demonstrated as an excellent mode-locker in an erbium-doped soliton fiber laser. Formation of the self-assembled membrane is attributed to hydrophobic nature of graphene and considerable capillary force. Experiments showed that such graphene saturable absorbers with insertion loss less than 6 dB worked well in the laser cavity setup, verifying that the self-assembly method is reliable and practical. Moreover, the method is quite facile, cost-effective, and potentially suitable for large-scale production of graphene mode-lockers. View full abstract»

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  • Enhancement in Light Extraction of GaN-Based Light-Emitting Diodes With High Reflectivity Electrodes

    Publication Year: 2011 , Page(s): 1793 - 1795
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    In GaN-based light-emitting diodes (LEDs), using gold-based metals to serve as electrodes, light absorption is a problem that severely restricts the light extraction in LEDs. This study demonstrates the GaN-based LEDs with high reflectivity metals (Ag/Pt) onto an n-type GaN surface and transparent contact layer (indium-tin-oxide), to serve as the n-type electrode and the p-type electrode, respectively. By replacing Cr/Au with Ag/Pt to serve as electrodes of LEDs, the light output power of the LEDs was increased by 15.7%, thereby significantly reducing the manufacturing cost of LEDs. View full abstract»

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  • Dynamic Sleep-Mode ONU With Self-Sustained Fast-Lock CDR IC for Burst-Mode Power Saving in 10 G-EPON Systems

    Publication Year: 2011 , Page(s): 1796 - 1798
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (802 KB) |  | HTML iconHTML  

    A novel power saving optical network unit (ONU) employing a self-sustained fast-lock clock and data recovery (CDR) circuit IC for 10 Gigabit Ethernet passive optical network (10 G-EPON) is presented. With its self-generated quasi-synchronized signal-based bursty CDR control, a fast wake-up time of the ONU within 497 ns supporting heavy-duty dynamic bandwidth allocation (DBA) cycles is fully achieved. A high power consumption reduction efficiency of 63.8%, compared to the typical Doze-mode power saving ONU, was also realized. View full abstract»

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  • 10-Gb/s Error-Free Silicon Optical Modulator for Both TE and TM Polarized Light

    Publication Year: 2011 , Page(s): 1799 - 1801
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (609 KB) |  | HTML iconHTML  

    We report the first experimental demonstration of a silicon optical modulator based on a pipin diode integrated in a 50- μm radius ring resonator. Large modulation efficiency was obtained with a VπLπ product of 3 V· cm for both transverse-electric (TE) and transverse-magnetic (TM) input light. Insertion loss of the doped ring resonator was lower than 1 dB and 10-Gb/s operations was demonstrated with an extinction ratio of 5.9 dB for TE and of 5.3 dB for TM polarization. A bit-error rate (BER) lower than 10-9 was measured in both TE and TM polarizations, proving the potential application of the modulator in optical transmission systems. View full abstract»

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  • 20-Gb/s Single-Feeder WDM-PON Using Partial-Response Maximum Likelihood Equalizer

    Publication Year: 2011 , Page(s): 1802 - 1804
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (615 KB) |  | HTML iconHTML  

    Wavelength-division-multiplexed passive optical network (WDM-PON) has been recognized as a future proof access solution. Reflective semiconductor optical amplifier (RSOA) is often employed for colorless operation of the optical network unit (ONU). However, the small electrical bandwidth of RSOA limits the speed of uplink. Moreover, chromatic dispersion together with high chirp of the directly modulated signal limits the upstream transmission distance. In addition, in-band crosstalk arising from reflections further limits the performance of a single fiber loop-back system. In this letter, characteristics of high-capacity RSOA-based WDM-PON in bidirectional architecture are experimentally studied. To overcome the constraints on uplink, we propose a novel receiver based on a partial-response maximum likelihood (PRML) equalizer. The 20-Gb/s operation of 1-GHz RSOA is demonstrated for a bidirectional distance up to 20 km. Furthermore, the proposed PRML equalizer is compared with other equalizers in various experiments to demonstrate its superior performance. View full abstract»

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  • A Silicon Balanced Subharmonic Optoelectronic Mixer for 60-GHz Fiber-Wireless Downlink Application

    Publication Year: 2011 , Page(s): 1805 - 1807
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (566 KB) |  | HTML iconHTML  

    We demonstrate a 60-GHz fiber-wireless downlink using a balanced subharmonic optoelectronic mixer based on a silicon avalanche photodiode (APD) pair fabricated with standard 0.25-μm bipolar complementary metal-oxide-semiconductor technology. Conversion efficiency of this new type of optoelectronic mixer is 11 dB better than that of the previously reported single APD mixer. We achieve downlink transmission of 25-Mb/s 32 quadrature-amplitude modulation data with the minimum error-vector magnitude of 2.4%. View full abstract»

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  • Towards Polarization Diversity on the SOI Platform With Simple Fabrication Process

    Publication Year: 2011 , Page(s): 1808 - 1810
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB) |  | HTML iconHTML  

    We present a polarization diversity circuit built on the silicon-on-insulator (SOI) platform, which can be fabricated by a simple process. The polarization diversity is based on two identical air-clad asymmetrical directional couplers, which simultaneously play the roles of polarization splitter and rotator. A silicon polarization diversity circuit with a single microring resonator is fabricated on the SOI platform. Only <;1-dB polarization-dependent loss is demonstrated. A significant improvement of the polarization dependence is obtained for 20-Gb/s nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) demodulation using the polarization diversity circuit, compared to a single microring resonator without polarization diversity. View full abstract»

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Aims & Scope

This letters journal addresses all aspects of the IEEE Photonics Society Constitutional Field of Interest with emphasis on photonic/lightwave components and applications, laser physics and systems and laser/electro-optics technology.

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Meet Our Editors

Editor-in-Chief
Dr. Seb J. Savory
University College London