By Topic

Photonics Technology Letters, IEEE

Issue 12 • Date June15, 2011

Filter Results

Displaying Results 1 - 25 of 33
  • [Front cover]

    Publication Year: 2011 , Page(s): C1
    Save to Project icon | Request Permissions | PDF file iconPDF (242 KB)  
    Freely Available from IEEE
  • IEEE Photonics Technology Letters publication information

    Publication Year: 2011 , Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (38 KB)  
    Freely Available from IEEE
  • Table of contents

    Publication Year: 2011 , Page(s): 757 - 758
    Save to Project icon | Request Permissions | PDF file iconPDF (165 KB)  
    Freely Available from IEEE
  • Simultaneous Generation of Two Sets of Time Delay Signature Eliminated Chaotic Signals by Using Mutually Coupled Semiconductor Lasers

    Publication Year: 2011 , Page(s): 759 - 761
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB) |  | HTML iconHTML  

    Simultaneous generation of two sets of time delay (TD) signature suppressed chaotic signals is experimentally demonstrated by using a mutually delay-coupled semiconductor laser (MDC-SL) system. The experimental results show that under proper conditions, TD signatures of chaotic output signals in such a system can be eliminated, and two sets of low TD signature chaotic signals can be simultaneously obtained. Furthermore, both the TD signature evolution pattern and the optimum scope for TD signature elimination are experimentally specified by modulating the coupling strength and adjusting frequency detuning between the two mutually coupled lasers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Packaged Monolithic Silicon 112-Gb/s Coherent Receiver

    Publication Year: 2011 , Page(s): 762 - 764
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (975 KB) |  | HTML iconHTML  

    Using a Si photonic integrated circuit and separate SiGe transimpedance amplifiers, we created a high-performance dual-polarization, dual-quadrature coherent receiver. It requires only 16.3-dB optical signal-to-noise ratio to receive a 112-Gb/s polarization-division-multiplexed quadrature phase-shift keying signal at a 10-3 bit-error rate. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Silicon Waveguide Integrated Germanium JFET Photodetector With Improved Speed Performance

    Publication Year: 2011 , Page(s): 765 - 767
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB) |  | HTML iconHTML  

    This letter reports our recent results on the high-speed silicon-waveguided germanium junction-field-effect-transistor (JFET)-based photodetector. Although the Ge layer's footprint on wafer is as small as 2 μm × 2 μm, low standby current (0.5 μA at 1 V), high responsivity (642 mA/W), and high speed (8 GHz) are achieved. The reported Ge JFET is a promising solution for photodetector's further scaling-down. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 3\times 2 ^{N} -QAM Constellation Formats for DMT Over 1-mm Core Diameter Plastic Optical Fiber

    Publication Year: 2011 , Page(s): 768 - 770
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (751 KB) |  | HTML iconHTML  

    The family of 3 × 2N quadrature amplitude modulation (QAM) constellations in combination with discrete multitone modulation is employed to maximize the throughput of 1-mm core diameter plastic optical fibers. Using this scheme together with a bit and power loading algorithm, a bit-rate improvement of 12% is achieved compared with using only 2N-QAM scheme. A bit rate of 5.6 Gb/s is demonstrated over 50 m of 1-mm core diameter graded-index plastic optical fiber (POF). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Flexible Shear Sensor Based on Embedded Optoelectronic Components

    Publication Year: 2011 , Page(s): 771 - 773
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (471 KB) |  | HTML iconHTML  

    Tactile shear stresses play an important role in the medical field and robotics. To monitor these stresses in situ, there is a need for unobtrusive flexible sensors that can be wrapped around curved surfaces or moving body parts. The presented sensor is based on changing coupling of optical power between a vertical-cavity surface-emitting laser (VCSEL) and a photodiode facing each other and separated by a deformable transducer layer. The required optoelectronic components were embedded in a polymer foil of only 40 μm thick, yielding a very thin and flexible total sensor stack of 250 μm thick. In the linear part of the range (between 2 and 5.5 N), the sensitivity of the prototype was -350 μA/N; the maximum measurable force was 5.5 N. However, by selecting the appropriate deformable sensor transducer material, the sensitivity and range can be tuned for a specific application. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Room-Temperature GaAs/AlGaAs Quantum Cascade Lasers Grown by Metal–Organic Vapor Phase Epitaxy

    Publication Year: 2011 , Page(s): 774 - 776
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (690 KB) |  | HTML iconHTML  

    We demonstrate λ ~ 9 μm GaAs/Al0.45Ga0.55As quantum cascade lasers (QCLs) operating up to 320 K. Metal- organic vapor phase epitaxy has been used throughout for the growth of the devices. Detailed comparison has been carried out for the QCLs with various waveguides and grown on (100) GaAs substrates with different miscut angles towards (111)A. Introduction of InGaP cladding layers into the optical waveguide significantly improves the QCL performance due to a better optical confinement and lower waveguide losses compared with the GaAs-based waveguide. A 20- μm-wide 4-mm-long device with high reflectivity coating on the laser back facet demonstrates room-temperature pulsed output power of 220 mW and a lowered threshold current density of 6.5 kA/cm2. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • GaSb-Based Semiconductor Disk Laser With 130-nm Tuning Range at 2.5 \mu m

    Publication Year: 2011 , Page(s): 777 - 779
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB) |  | HTML iconHTML  

    We demonstrate a GaSb-based semiconductor disk laser emitting 0.6 W of output power at 2.5 μm in a fundamental mode regime (M2 <; 1.6). A gain structure grown by molecular beam epitaxy and assembled with an intracavity diamond heat spreader demonstrates a promising potential for power scaling and broad wavelength tuning. A tuning range of 130 nm with output power up to 310 mW has been achieved which represents the largest spectral coverage reported to date for disk lasers at this wavelength. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time-Resolved Response of Polymer Bulk-Heterojunction Photodetectors

    Publication Year: 2011 , Page(s): 780 - 782
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (455 KB) |  | HTML iconHTML  

    We have fabricated a polymer bulk-heterojunction photodetector from a (1:0.7) blend solution of poly(3-hexyl-thiophene) (P3HT) and 1-(3-methoxy-carbonyl)propyl-1-phenyl-(6, 6)C-61 (PCBM) in o-dichlorobenzene. Absorption spectrum, external quantum efficiency and current-voltage (I-V) curves, both in dark condition and under illumination of a narrowband green light-emitting diode (green-LED) with λem,peak center at 525 nm, were measured to characterize the photodiode behavior. Moreover, the time-resolved response under the green-LED stimulus modulated at 200 KHz has been measured. This result suggests the application of our device as organic photodetector for all-organic optical data link in low-cost plastic-optical-fiber-based systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Filter-Less Amplification for Rapid Swept-Wavelength Interferometric Measurement of Silicon Waveguide Group Delay Statistics

    Publication Year: 2011 , Page(s): 783 - 785
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (366 KB) |  | HTML iconHTML  

    In the context of rapid and high-resolution swept-wavelength interferometric measurement of dispersion properties of silicon nanophotonic devices, we show that filter-less optical amplification does not perturb the measured statistical distributions of group delay. The scaling behavior of group delay ripple with detected power is also shown to be identical for the unamplified and filter-less amplified cases. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Highly Efficient and Broadband Cherenkov Radiation at the Visible Wavelength in the Fundamental Mode of Photonic Crystal Fiber

    Publication Year: 2011 , Page(s): 786 - 788
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (455 KB) |  | HTML iconHTML  

    Highly efficient and broadband Cherenkov radiations (CRs) by soliton self-frequency shift (SSFS) are generated in the fundamental mode of photonic crystal fiber (PCF) fabricated in our laboratory. The dependences of CR on the pump wavelength and power are investigated, and the corresponding nonlinear-optical processes are discussed. When the average power of the 120-fs pump pulse increases from 100 to 300 mW, the Raman soliton shifts from 1970 to 2130 nm, the conversion efficiency of CR in the range of 580 to 545 nm increases from 8% to 31%, and the width of output optical spectrum at the visible wavelength broadens from 11 to 54 nm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimization of Vector Signal Delivery Over Double-Sideband Carrier-Suppressed Optical Millimeter-Waves Through DC Coupling

    Publication Year: 2011 , Page(s): 789 - 791
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB) |  | HTML iconHTML  

    A novel vector signal transmission scheme through double-sideband carrier-suppressed (DSB-CS) radio-over-flber system is proposed and experimentally demonstrated. Traditionally, the single-stage DSB-CS optical millimeter (mm)-wave generation scheme could not deliver a vector signal due to the loss of phase information at the receiver. However, we found that by simply adding dc offset to the transmitting vector signal, the desired signal after beating at the receiver can be preserved and enhanced without introducing any hardware complexity to existing systems. A feasibility demonstration of transmitting a 200-Mb/s quadrature phase-shift-keying orthogonal frequency-division-multiplexing (QPSK-OFDM) signal on 60-GHz optical mm-wave over 10-km standard single-mode fiber (SSMF) has been successfully completed with a demodulated error vector magnitude (EVM) less than 5.52% in our experiment. In addition, the value of the required dc offset and its impact to the system performance is also experimentally investigated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Block-Diagonal MIMO Equalization for Polarization-Multiplexed OFDM Transmission With Direct Detection

    Publication Year: 2011 , Page(s): 792 - 794
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (365 KB) |  | HTML iconHTML  

    We propose a novel digital signal processing (DSP)-based multiple-input-multiple-output (MIMO) equalization algorithm set for polarization-multiplexed orthogonal frequency-division multiplexing transmission with direct detection (POLMUX-OFDM-DD), based on block-diagonal matrix processing. The new methodology significantly reduces legacy zero forcing (ZF)-based equalization complexity, and enables performance gains via efficient minimum mean square error (MMSE) and maximum likelihood (ML) detection. The new block-diagonal MMSE and ML algorithms are experimentally shown to extend transmission distance from 870 to 900 km and beyond 960 km, respectively, in 20-Gb/s standard single-mode fiber (SSMF) POLMUX OFDM quadrature-phase-shift-keying (QPSK)-DD transmission. The new algorithms are highly attractive for future cost-efficient, DSP-based optical metro/access systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mach–Zehnder Photonic Crystal Interferometer in Cavity Ring-Down Loop for Curvature Measurement

    Publication Year: 2011 , Page(s): 795 - 797
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (631 KB) |  | HTML iconHTML  

    Abstract-An all-fiber Mach-Zehnder interferometer curvature sensor fabricated by collapsing both ends of a photonic crystal fiber connected to a single-mode fiber is described. The interferometer is inscribed into the cavity ring-down loop and shows high sensitivity of 0.7311(μs)-1 · m and high repeatability when a curvature of 0.4135 to 0.8122 m-1 is applied. High correlation value of 0.997 is obtained with low standard error of 1.05%. This corresponds to a minimum detectable curvature of 4.849 × 10-3 m-1. The proposed sensor also displays low sensitivity to temperature with a value of 0.0008(μs ·° C)-1. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reduction of Efficiency Droop in InGaN Light-Emitting Diode Grown on Self-Separated Freestanding GaN Substrates

    Publication Year: 2011 , Page(s): 798 - 800
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (551 KB) |  | HTML iconHTML  

    Using a GaN nanorod template in a hydride vapor phase epitaxy (HVPE) system can manufacture a freestanding GaN (FS-GaN) substrate with threading dislocation densities down to ~ 107 cm-2. In this letter, we report InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) grown on this FS-GaN substrate. The defect densities in the homoepitaxially grown LEDs were substantially reduced, leading to improved light emission efficiency. Compared with the LED grown on sapphire, we obtained a lower forward voltage, smaller diode ideality factor, and higher light-output power in the same structure grown on FS-GaN. The external quantum efficiency (EQE) of LEDs grown on FS-GaN were improved especially at high injection current, which brought the efficiency droop phenomenon greatly reduced at high current density. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient Complex Envelope ADI-FDTD Method for the Analysis of Anisotropic Photonic Crystals

    Publication Year: 2011 , Page(s): 801 - 803
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (679 KB) |  | HTML iconHTML  

    This letter presents a new efficient formulation of the recently proposed complex envelope alternating direction implicit finite-difference time-domain (CE-ADI-FDTD) method for anisotropic photonic crystal (PhC) analysis. The proposed CE-ADI-FDTD method is based on a concise E-H formulation that is more efficient and simpler to implement compared to the conventional method. The concise formulation includes perfectly matched layer (PML) boundary conditions and caters for nonuniform grid discretization. The efficiency of the proposed CE-ADI-FDTD method is validated through a numerical study of the field enhancement effect in a finite sized PhC composed of periodic cells of misaligned anisotropic dielectric layers with split band edge (SBE) on the band diagram. In the numerical study, we further illustrate that by properly tuning the orientation angles of the anisotropy axes of the SBE PhC layers, the field enhancement effect can be optimized for an incident wave polarization. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Temperature-Independent Curvature Sensor Using FBG Cladding Modes Based on a Core Misaligned Splice

    Publication Year: 2011 , Page(s): 804 - 806
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (446 KB) |  | HTML iconHTML  

    A fiber-optic curvature sensor based on a core offset single-mode fiber (SMF) combined with a fiber Bragg grating (FBG) is presented. The FBG cladding modes are efficiently excited by the large core misalignment. The curvature of the fiber can be obtained by the ratio between the recoupled cladding mode power and the reflected core mode power. These measurements are independent from temperature variation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adiabatic Mode Conversion in Multimode Waveguides Using Chirped Computer-Generated Planar Holograms

    Publication Year: 2011 , Page(s): 807 - 809
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (685 KB) |  | HTML iconHTML  

    We discuss the design of a mode converter based on optical analogy of adiabatic passage via a level crossing in multimode waveguides. Computer-generated planar holograms are used to implement the chirped gratings that mimic the laser excitation used in the transfer between quantum states of atoms and molecules. The mode coupling properties are analyzed using the coupled mode theory and shown to resemble the level crossing process. Key features of the devices are illustrated with theoretical calculations and numerical examples. The proposed mode converter shows a bandwidth in excess of 300 nm in the optical communications band. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-Capacity Wireless Signal Generation and Demodulation in 75- to 110-GHz Band Employing All-Optical OFDM

    Publication Year: 2011 , Page(s): 810 - 812
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB) |  | HTML iconHTML  

    We present a radio-frequency (RF) and bit-rate scalable technique for multigigabit wireless signal generation based on all-optical orthogonal frequency-division multiplexing (OFDM) and photonic up-conversion. Coherent detection supported by digital signal processing is used for signal demodulation and data recovery. In order to demonstrate the RF frequency scalability and bit-rate transparency, the system is tested at 60 GHz and in the 75- to 110-GHz band at the baud rates of 5 and 10 Gbaud. In terms of the bit rate, the proposed system is experimentally tested up to 40 Gb/s for wireless signal generation and demodulation. The wireless transmission is not considered in this letter. Additionally, a novel digital carrier phase/frequency recovery structure is employed to enable robust phase and frequency tracking between the beating lasers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Generation of Two-Dimensional Optical Reference Signals Based on Parametric Minimum Cross Entropy

    Publication Year: 2011 , Page(s): 813 - 815
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (533 KB) |  | HTML iconHTML  

    In this letter, a novel design of two-dimensional (2-D) zero reference codes (ZRCs) based on parametric minimum cross entropy (PMCE) is proposed to generate 2-D optical zero reference signals (ZRSs) with low second maximum for grating alignment systems. An optical ZRS is necessary to obtain an absolute measurement in grating alignment systems. A method to acquire an optical ZRS is by means of illuminating two identical superimposed ZRCs. Because the movement between the two ZRCs is in two-axis, 2-D ZRCs are required. However, they are hard to design due to the high computational complexity, especially for large codes. The proposed PMCE method not only reduces the second maximum of 2-D optical ZRSs, but also decreases the computational complexity. Simulation results indicate that there are 8.33% ~ 22.22% reductions in the second maximum of several 2-D optical ZRSs, as compared with those of the recently proposed cross-entropy (CE) method. The PMCE method proves to be a powerful tool for the design of 2-D ZRCs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 4H-SiC Nano-Pillar Avalanche Photodiode With Illumination-Dependent Characteristics

    Publication Year: 2011 , Page(s): 816 - 818
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (491 KB) |  | HTML iconHTML  

    A 4H-SiC nano-pillar-based avalanche photodiode (NAPD) with a separate absorption region and a multiplication region is proposed and its optoelectronic performance is modeled. By properly designing the device geometry and the doping concentration of each layer, the avalanche breakdown voltage (Vbr) of the NAPD is found to be dependent of the incident wavelength and power density, which are explained by the band diagrams of 4H-SiC NAPDs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Long-Distance Demonstration and Modeling of Low-Power Silicon Microdisk Modulators

    Publication Year: 2011 , Page(s): 819 - 821
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (531 KB) |  | HTML iconHTML  

    Silicon micro-resonators have been proposed for short-distance intracomputer interconnects and recently for long-distance communications. In this letter, the spectral profile, chirp, and power penalties are theoretically analyzed, measured, and compared for a recent silicon microdisk resonator technology. Theory predicts negative pulse chirping of the transmitted wave which when combined with the dispersion properties of SMF-28 fiber results in no power penalty at 40 km and less than 1 dB for 70 km at 5 Gb/s. The measurement at 5 Gb/s agrees with the theoretically predicted values. Measurement of the modulator at a bandwidth limited speed of 10 Gb/s results in 2- and 6.5-dB power penalties at 40 and 70 km, respectively. Comparison with commercial Mach-Zehnder modulator (MZM) technology at 70 km shows that the silicon microdisk is within 0.5-dB power penalty of the MZM at 5 Gb/s and within 4 dB of the MZM power penalty at 10 Gb/s. Theory and experimental results show silicon photonic modulators can be competitive options for long-distance communications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical Simulation of Single-Junction In _{0.5} Ga _{0.5} P Solar Cell With Compositional Grading Configuration

    Publication Year: 2011 , Page(s): 822 - 824
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB) |  | HTML iconHTML  

    A compositional grading layer between the p-In0.5Ga0.5P emitter layer and p-In0.5Al0.5P window layer in the p+-n In0.5Ga0.5P solar cell is investigated numerically. With the insertion of the grading layer, the short-circuit current density and conversion efficiency are improved due to the enhancement of carrier-collection efficiency, which can be ascribed to the reduction of potential barrier height in the valance band and the existence of internal quasi-electric field in the conduction band. An optimized value of conversion efficiency can be obtained by appropriately adjusting the thickness of the grading layer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

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