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Photonics Technology Letters, IEEE

Issue 8 • Date April15, 2014

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Displaying Results 1 - 25 of 32
  • [Front cover]

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

    Page(s): C2
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    Freely Available from IEEE
  • Table of contents

    Page(s): 743 - 744
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  • A Longwave Infrared Focal Plane Array Enhanced by Backside-Configured Plasmonic Structures

    Page(s): 745 - 748
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (566 KB) |  | HTML iconHTML  

    We demonstrate a 320 × 256 longwave infrared focal plane array (FPA) enhanced by backside-configured surface plasmonic structures. The backside-configured plasmonic structures were fabricated on the photodetector side rather than the substrate side. The backside plasmonic FPA shows an average noise-equivalent temperature difference (NEΔT) of 110 mK with a standard deviation σ of 11.09 mK at the blackbody temperature of 30°C. Over 50% improvement in NEΔT is obtained by the backside plasmonic structures. Since the backside configured plasmonic structures can be fabricated on the photodetector side before the substrate lapping and removing, the difficulty of fabricating a plasmonic FPA is greatly reduced. View full abstract»

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  • Fiber Fabry–Pérot Interferometers Based on Air-Bubbles/Liquid in Hollow Core Fibers

    Page(s): 749 - 752
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (921 KB) |  | HTML iconHTML  

    This letter develops a miniature and highly sensitive fiber Fabry-Pérot interferometer (FFPI) that is based on an air-bubble and liquid in a hollow core fiber (HCF). The endface of the proposed FFPI is sealed off by an optical fiber plug to ensure the optical/chemical stability of the used liquids. The fiber plug is fabricated with a single-mode fiber taper to close the end of the liquid core fiber. The proposed technique ensures that the filled liquid neither effuses nor becomes contaminated. Experimental results show that the presence of both an air-bubble and liquid in the FFPI enables the highly sensitive measurement of temperature (T), the sensitivity of which can be controlled by changing the ratio of the volume of air to that of liquid in the HCF. View full abstract»

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  • Multidimensional Constellations for Power-Efficient and Flexible Optical Networks

    Page(s): 753 - 756
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (599 KB) |  | HTML iconHTML  

    Multidimensional constellations and time domain hybrid QAM both realize a non-integer ratio of bits per complex 2D symbol in order to allow for flexibility of spectral efficiency. We compare both approaches in terms of symbol error probability, asymptotic power efficiency, and bit error probability. In order to achieve 400G transmission, as an example for a non-integer ratio, an average number of 3.33 bits per complex 2D symbol was chosen, resulting in a symbol rate of 67.2 GBd including 12% FEC overhead. We show a 0.34-dB gain of multidimensional 16-QAM modulation over a hybrid 8-QAM/16-QAM scheme in terms of asymptotic power efficiency. View full abstract»

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  • Fiber-Optic Temperature Sensor Using a Fabry–Pérot Cavity Filled With Gas of Variable Pressure

    Page(s): 757 - 760
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB) |  | HTML iconHTML  

    We report a high-temperature fiber-optic sensor based on measuring the spectral fringes of a Fabry-Pérot (FP) cavity on a microstructure fiber (MF) when the gas pressure in the cavity is varied through the holes in the MF. Theoretical analysis shows that the absolute temperature can be deduced from the slope of the spectral shift versus pressure curve, which requires no calibration and is insensitive to the FP cavity length variations. For demonstration, we fabricated a miniature sensor whose FP cavity is formed by sandwiching a fuse-silica tube between a side-hole MF and a solid-core fiber. Using the holes in the MF as gas channels, the pressure in the FP cavity is controlled. The sensor was tested for operation above 1000°C. Strain-insensitive temperature measurement was demonstrated at ambient temperature for a strain range up to 3600 με. View full abstract»

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  • Large-Signal RF Circuit Model for a High-Power Laser Diode Module

    Page(s): 761 - 764
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (583 KB) |  | HTML iconHTML  

    An electrical large-signal circuit model for a 30-W high-power laser diode module is presented. Such modules are designed primarily for continuous wave (cw) operation but can be pulsed in the sub- μs temporal range for special applications. Our model is thus valid up to 20 MHz in the electrical frequency domain. The elements of the circuit model have been derived from RF impedance measurements using a calibrated vector network analyzer and a high-current dc/RF bias-T. The impedance is dominated by the inductance of the high-current connecting leads from the laser driver to the laser chip. The skin effect has been found to influence considerably both resistive and inductive impedances at high frequencies. For large-signal circuit simulations in the time domain, the current-voltage characteristic of the diode p-n junction is included by an analytic equation. The model is verified by comparison of simulation results with measured currents, voltages, and laser powers in large-signal pulsed-mode operation. This model is well suited for the design of optimized pulsed-current driver circuits. View full abstract»

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  • 28-GBd 32QAM FMF Transmission With Low Complexity Phase Estimators and Single DPLL

    Page(s): 765 - 768
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1013 KB) |  | HTML iconHTML  

    As spatial division multiplexed transmission systems employing few mode fibers (FMFs) rely heavily on digital signal processing (DSP), the impact of computational complexity should be considered. A key DSP process block is the carrier phase estimation (CPE), which consists of a phase estimator and digital phase locked loop (DPLL) per output. In this letter, a low complexity phase estimator is proposed, and the common-mode laser frequency offset is exploited to reduce the number of DPLLs. The combination of a low complexity CPE and single DPLL is experimentally demonstrated for a 28 GBd six-channel transmission over a 41.7-km FMF, carrying up to 32 quadrature amplitude modulation. Thereby, the nonlinear tolerances for the proposed CPE scheme are shown to perform similarly as the more computationally complex conventional CPE scheme. View full abstract»

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  • Vector Soliton Generation in a Tm Fiber Laser

    Page(s): 769 - 772
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB) |  | HTML iconHTML  

    Vector soliton generation is experimentally demonstrated in an all-fiber Tm/Ho-doped fiber laser operated at 1951 nm. To the best of our knowledge, it is the first clear evidence of group-velocity-locked vector soliton formation around 2 μm. Numerical simulation well reproduces the experimental observation and suggests that the central wavelength shift between the two orthogonal polarized components of the vector soliton is determined by the cavity birefringence. The central wavelength shift increased with the increasing of the cavity birefringence. However, the vector solitons become linearly polarized if the cavity birefringence is too strong. Experimental observation and numerical simulations both suggest that the vector soliton generation is wavelength independent. View full abstract»

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  • Technology Options for 400 Gb/s PM-16QAM Flex-Grid Network Upgrades

    Page(s): 773 - 776
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1043 KB) |  | HTML iconHTML  

    In this letter, we report on 400 Gb/s polarization multiplexed 16-state quadrature amplitude modulation (PM-16QAM) transponder variants and flex-grid network upgrade configurations. We address transponder subcarrier granularity, and demonstrate that the performance improvement, from dual-carrier to quad-carrier super-channel configuration, is limited to ~ 1.4 dB (in Q-factor, at power spectral density of 10-1 mW/GHz), at the cost of doubled hardware requirements. In view of that, we establish the performance improvements, for a dual-carrier 400 Gb/s PM-16QAM transceiver, as a function of increasing forward error correction overhead (FEC-OH) and spectral inversion based super-channel fiber nonlinearity compensation (SNLC-SI). We show that increasing the FEC-OH improves the transmission performance, at the cost of significant power consumption requirements, alternatively, employing SNLC-SI, at a lower FEC-OH, is a more power efficient solution. In particular, for homogeneous and heterogeneous launch power based network configurations, SNLC-SI enables ~ 23% and ~ 45% reach improvements at maximum considered FEC-OH (45%). At a fixed distance, it enables ~ 25% and ~ 50% power savings, respectively, compared with FEC-OH employing linear compensation only. View full abstract»

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  • Gold Nanoparticles-Modified Tapered Fiber Nanoprobe for Remote SERS Detection

    Page(s): 777 - 780
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (483 KB) |  | HTML iconHTML  

    This letter presents a surface-enhanced Raman scattering (SERS) nanoprobe based on gold nanoparticles-modified tapered optical fiber and demonstrates its ability to perform remote Raman detection. The nanoscale tapered fiber with the tip size of 40.7 nm was made by heated pulling and chemical etching methods. The gold nanoparticles, prepared beforehand by the Frens method with a microwave heating process, were deposited on the tapered surface of the nanoprobe with the electrostatic self-assembly technology. Raman spectra of Rhodamine 6G (R6G) molecules were measured, using this SERS nanoprobe in an optrode remote detection mode. Considerably high signal-to-noise ratio and high sensitivity were achieved. The detection limit for R6G aqueous solution reaches 10-8 mol/L. View full abstract»

    Open Access
  • Energy-Efficient Brightness Control and Data Transmission for Visible Light Communication

    Page(s): 781 - 784
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1144 KB) |  | HTML iconHTML  

    This letter considers the efficient utilization of energy in a visible light communication (VLC) system. A joint brightness control and data transmission are presented to reduce the total power consumption while satisfying lighting and communication requirements. An optimization problem is formulated to determine the optimal parameters for the input waveform of light emitting diode (LED) lamps; this problem reduces the total energy consumption of the LED lamps while ensuring the desired brightness and communication link quality. The simulation results show that the proposed scheme increases the energy efficiency of the VLC system. View full abstract»

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  • Multifunctional Optical Filter Using Direct-Coupled and Cross-Coupled All-Pass Filters

    Page(s): 785 - 788
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (771 KB) |  | HTML iconHTML  

    We present a multifunction optical filter that operate as: 1) symmetric interleaver (SI); 2) asymmetric interleaver (AI); 3) dual-wavelength, channel passing add-drop filter (ADF); and 4) dual-wavelength, channel dropping ADF. The new filter is a pair of direct-coupled all-pass-filter (APF) and cross-coupled APF positioned in each of the two arms of a Mach-Zehnder interferometer (MZI). Depending on the MZI's path length difference and the values of the coupler's coefficients, these four functions are demonstrated. The interleaver has a superior flat-top profile, low ripple value ( -0.095 dB for SI, -0.075 dB for AI), and high extinction ratio . The effect on waveguide losses on flat-top, ripple, slope, and SNR are also investigated. View full abstract»

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  • Probing Surface Structure Quality of ZnO Nanorods by Second Harmonic Generation

    Page(s): 789 - 792
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (706 KB) |  | HTML iconHTML  

    The surface quality of ZnO nanorod after postannealing was inspected by second harmonic generation (SHG) with the assistance of photoluminescence (PL) spectra, and the X-ray photoelectron (XPS) spectroscopy. The SHG is sensitive to the quality of the surface structure, which involves the elimination of surface defects and restructuring. Oxygen (O)-deficient defects and surface defects were generated during the growth of ZnO nanorods. The PL and XPS analyses indicate that the surface defects on ZnO nanorods were reduced at annealing temperatures above 600 °C. The bulk crystal structure was repaired for higher activation temperatures (> 700°C) concluded by X-ray diffraction. Results from SHG revealed the relationship between surface restructuring of ZnO nanorods and annealing temperature. View full abstract»

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  • Using an Analytical Model to Design Liquid Crystal Microlenses

    Page(s): 793 - 796
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (594 KB) |  | HTML iconHTML  

    We have developed new analytical expressions for designing liquid crystal (LC) microlenses. These equations are based on a novel equivalent electric circuit and can be used to create an optimum design for the LC lenses in which the lens diameter ranges from a few micrometers to several millimeters. Thus far, only experimental studies have been conducted on the LC lenses. The analytical expressions developed in this letter depend on various manufacturing parameters and can be used to design lenses with specific focal lengths and a parabolic phase profile. The required driving scheme (modal or hole-patterned) can be predicted. The LC microlenses were manufactured and electrooptically characterized: the measurements were compared using an analytical approach. View full abstract»

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  • Pump-Power-Independent Double Slope-Assisted Distributed and Fast Brillouin Fiber-Optic Sensor

    Page(s): 797 - 800
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2344 KB) |  | HTML iconHTML  

    A small modification of the fast and distributed slope-assisted Brillouin time domain analysis (SA-BOTDA) method allows it to easily implement pump-power independent measurements of strain and/or temperature, using the ratio between readings taken on both slopes of the Brillouin gain spectrum. Employing this new double SA-BOTDA measurement technique, fast (${sim}{rm 100}~{rm Hz}$ at ${sim}{rm 1}hbox{-}{rm kHz}$ effective sampling rate) strain measurements are shown to be immune to pump pulse power variations as large as 6 dB. At the expense of halving the sampling rate, this technique still maintains all the benefits of its SA-BOTDA predecessor. In particular, its ability to handle (Brillouin) longitudinally inhomogeneous fibers is demonstrated. View full abstract»

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  • Seamless Sub-Band Wavelength Conversion of Tb/s-Class CO-OFDM Superchannels

    Page(s): 801 - 804
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (741 KB) |  | HTML iconHTML  

    We experimentally demonstrate a sub-band wavelength conversion scheme based on four-wave mixing in high-nonlinear fiber for multiple Tb/s-class superchannel coherent optical orthogonal frequency-division multiplexing networks. Combined with the wavelength selective switches in reconfigurable optical add/drop multiplexers, the overlapped spectra are efficiently relocated and almost seamlessly formed into a new superchannel with very little spectral efficiency degradation. View full abstract»

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  • Digital Phase Noise Cancellation for a Coherent-Detection Microwave Photonic Link

    Page(s): 805 - 808
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (935 KB) |  | HTML iconHTML  

    An intensity-modulation and coherent-detection (IM/CD) microwave photonic (MWP) link with digital signal processing (DSP)-based phase noise cancellation is proposed and experimentally demonstrated. At the transmitter, the optical carrier is intensity-modulated by a radio-frequency (RF) signal and sent to a coherent receiver over a single-mode fiber (SMF). At the receiver, the intensity-modulated optical signal is coherently detected using a local oscillator (LO) laser source. The phase noise introduced by both the transmitter laser source and the LO laser source is converted into an amplitude noise at the output of the coherent receiver, which would be added to the in-phase component and quadrature component from the coherent receiver. The noise can be completely cancelled by summing the squared magnitudes of the in-phase and quadrature components from the coherent receiver, which can be implemented using a DSP unit. Error-free transmission of a 1.25-Gb/s quadrature phase shift keying modulated RF signal with a center frequency of 1.6 GHz over 25-km SMF is experimentally demonstrated. For a signal with a bit rate of 834 Mb/s, the receiver sensitivity can reach ${-}{rm 24.5}~{rm dBm}$ which is 20 dB better than that based on an intensity-modulation and direct-detection MWP link. View full abstract»

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  • Integrated FTTH and In-Building Fiber-Coax OFDM Field Trial

    Page(s): 809 - 812
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1264 KB) |  | HTML iconHTML  

    The performance of multi-service provisioning employing orthogonal frequency division multiplexed (OFDM) signals in fiber-to-the-home (FTTH) networks integrating hybrid fiber-coax in-building distribution is evaluated with a field trial in Towercom FTTH network in operation in Bratislava, Slovakia. The optical link budget performance is evaluated on an FTTH link of 35.8 km of standard single-mode fiber including hybrid 100-m fiber and 20-m coax in-building distribution transmitting a five-in-one multi-service bundle. The multi-service OFDM bundle includes LTE for phone service provision, WiMAX for wireless data and home security, DVB-T and UWB for TV and HD video broadcasting, and a custom OFDM signal providing wired gigabit Ethernet (GbE) connectivity. The specific optical power level requirements for both downstream and upstream directions to achieve successful bi-directional communication are evaluated in a WDM-PON configuration. The experimental results indicate that multi-service downstream provision with ${-}{rm 5}hbox{-}{rm dBm}$ optical power arriving to customer premises is required. In the upstream, the optical power power requirement at the central office is ${-}{rm 9}~{rm dBm}$ for return communication. The optical attenuation level that can be supported by the network is investigated to evaluate the splitting ratio and the maximum capacity (number of users) of the network. Final application was confirmed experimentally with the transmission of multi-service OFDM signals in Towercom FTTH network including a 1:8 passive splitter. View full abstract»

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  • Fast-Tuning Coherent Burst-Mode Receiver for Metropolitan Networks

    Page(s): 813 - 816
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (790 KB) |  | HTML iconHTML  

    We demonstrate a fast wavelength-tunable burst-mode receiver for coherent 28 GBd dual-polarization quadrature phase shift keying signals using a commercially available DS-DBR laser as the local oscillator (LO). We find that the frequency drift and linewidth of the LO must be precisely controlled to prevent bit-error-ratio (BER) penalties when the signal undergoes transmission distances typical of metropolitan-area networks. We demonstrate reduction of the LO frequency drift and linewidth after wavelength switching by compensation using the phase section of the laser and achieve negligible BER penalty with burst-mode reception for single-mode fiber transmission up to 1280 km. We also measure the sensitivity of the receiver to LO detuning when multiple wavelength-division multiplexed channels are received simultaneously as in a broadcast-and-select network architecture. View full abstract»

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  • Dual-Parameter Sensor Based on Tapered FBG Combined With Microfiber Cavity

    Page(s): 817 - 820
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (978 KB) |  | HTML iconHTML  

    A hybrid sensor based on tapered fiber Bragg grating (FBG) combined with microfiber cavity tapered FBG combined with a microfiber cavity is proposed and demonstrated in this letter. It is fabricated by taper-drawing from a normal FBG. The FBG taper and microfiber end form an interferometric cavity. Temperature and refractive index (RI) can be measured simultaneously using such a hybrid structure. The temperature and RI variation are determined by the wavelength shift and fringe contrast change, respectively, thus the temperature and RI measurement base on the proposed structure is free of cross-sensitivity intrinsically. The obtained temperature sensitivity is ${sim}{rm 13}~{rm pm}/^{circ}{rm C}$ for temperature, whereas the RI sensitivity is ${sim}{rm 15}~{rm dB}$ /RIU for the RI range from 1.33 to 1.43. View full abstract»

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  • Comb-Based 16-QAM Transmitter Spanning the C and L Bands

    Page(s): 821 - 824
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (863 KB) |  | HTML iconHTML  

    A multiwavelength source for optical transmitters delivers narrow-linewidth carrriers with 100-GHz spacing spanning the C and L bands. The phase-locked carriers are derived from a single, 3-kHz linewidth source, and a multistage parametric mixer. Bit-error rate measurements for a 20-GBd 16-QAM transmitter based on this source are reported. View full abstract»

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  • Focusing Grating Couplers in Unmodified 180-nm Silicon-on-Insulator CMOS

    Page(s): 825 - 828
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (910 KB) |  | HTML iconHTML  

    The design and demonstration of photonic grating couplers with improved efficiencies monolithically integrated in IBM's 7RF silicon-on-insulator (SoI) complementary metal–oxide–semiconductor (CMOS) technology offering are reported. The grating couplers are fabricated using two standard layers available in 7RF SoI CMOS, where focusing circular grating structures and a small-footprint tapered slab are fabricated on the poly-silicon and crystalline-silicon (c-Si) layers, respectively. The coupling efficiencies for 1.3- and 1.55-$mu{rm m}$ grating couplers are measured to be ${-}{rm 2.8}$ and ${-}{rm 3.8}~{rm dB}$, respectively. These results are at least $2times$ more efficient than the best previously reported grating couplers in this technology, which were fabricated using c-Si layers only. Furthermore, the devices exhibit 1-dB bandwidths of ${sim}{40}$ and 52 nm for 1.3 and ${rm 1.55}~mu{rm m}$, respectively. View full abstract»

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  • Narrow Stripe Broad Area Lasers With High Order Distributed Feedback Surface Gratings

    Page(s): 829 - 832
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (793 KB) |  | HTML iconHTML  

    GaAs-based narrow-stripe broad-area lasers with integrated surface gratings are shown to operate with high power and efficiency, low beam parameter product (BPP), and narrow spectra. These distributed feedback lasers are constructed using a surface-etched, 80th-order grating, leading to spectral width $Deltalambda_{95%}<0.7~{rm nm}$ (95% power) and wavelength ${sim}{rm970}~{rm nm}$. Optical output powers $({>}{rm 6}~{rm W})$ and power conversion efficiencies $({>}{50%})$ comparable with devices without grating are enabled by a small coupling coefficient, $kappa{rm L}{sim}{0.3}$, consistent with coupled mode theory calculations. The lasers were constructed with a stripe width of 30 $mu{rm m}$, enabling BPP ${<}{rm 1.8}~{rm mm}$ mrad up to 6-W output power, improved over devices without gratings, that show BPP ${>}{rm 2.2}~{rm mm}$ mrad. We attribute the improvement to spatial filtering of higher order lateral modes by the narrow surface grating. Such devices are attractive sources for use in spectral beam combination systems for material processing. 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