Photonics

Editorial

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2 pages, 140 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Photonics in 2016

by Photonics Editorial Office

MDPI AG, St. Alban-Anlage 66, 4052 Basel, Switzerland

Photonics 2017, 4(1), 4; https://doi.org/10.3390/photonics4010004 - 10 Jan 2017

Viewed by 3236

Abstract

The editors of Photonics would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article

Research

Jump to: Editorial, Review

17 pages, 2293 KiB

Open AccessArticle

Generation and Detection of Continuous Variable Quantum Vortex States via Compact Photonic Devices

by David Barral^*

, Daniel Balado and Jesús Liñares

Optics Area, Department of Applied Physics, Faculty of Physics and Faculty of Optics and Optometry, University of Santiago de Compostela, Campus Vida s/n (Campus Universitario Sur), Santiago de Compostela, Galicia E-15782, Spain

Photonics 2017, 4(1), 2; https://doi.org/10.3390/photonics4010002 - 3 Jan 2017

Cited by 5 | Viewed by 5568

Abstract

A quantum photonic circuit with the ability to produce continuous variable quantum vortex states is proposed. This device produces two single-mode squeezed states which go through a Mach-Zehnder interferometer where photons are subtracted by means of weakly coupled directional couplers towards ancillary waveguides. [...] Read more.

A quantum photonic circuit with the ability to produce continuous variable quantum vortex states is proposed. This device produces two single-mode squeezed states which go through a Mach-Zehnder interferometer where photons are subtracted by means of weakly coupled directional couplers towards ancillary waveguides. The detection of a number of photons in these modes heralds the production of a quantum vortex. Likewise, a measurement system of the order and handedness of quantum vortices is introduced and the performance of both devices is analyzed in a realistic scenario by means of the Wigner function. These devices open the possibility of using the quantum vortices as carriers of quantum information. Full article

(This article belongs to the Special Issue Quantum Photonics Circuits)

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12 pages, 4102 KiB

Open AccessArticle

Optical Analysis of the Oils Obtained from Acrocomia aculeata (Jacq.) Lodd: Mapping Absorption-Emission Profiles in an Induced Oxidation Process

by Ivan P. De Oliveira¹, Willian A. Correa¹, Priscila V. Neves¹, Perla V. B. Silva¹, Caroline H. Lescano¹, Flávio S. Michels¹, Wilson E. Passos¹, Rozanna M. Muzzi¹, Samuel L. Oliveira²

and Anderson R. L. Caires^2,*

¹ Faculdade de Ciências Exatas e Tecnologia, Universidade Federal da Grande Dourados, 79804-970 Dourados-MS, Brazil

² Grupo de Óptica e Fotônica, Instituto de Física, Universidade Federal de Mato Grosso do Sul, 79070-900 Campo Grande-MS, Brazil

Photonics 2017, 4(1), 3; https://doi.org/10.3390/photonics4010003 - 6 Jan 2017

Cited by 18 | Viewed by 5727

Abstract

Acrocomia aculeata is a palm tree typical of the Brazilian savanna. Oils extracted from the pulp and kernel of Acrocomia aculeata fruits have gained considerable attention mainly due to their nutritional and medicinal features. Despite their potential applications, a detailed analysis of their [...] Read more.

Acrocomia aculeata is a palm tree typical of the Brazilian savanna. Oils extracted from the pulp and kernel of Acrocomia aculeata fruits have gained considerable attention mainly due to their nutritional and medicinal features. Despite their potential applications, a detailed analysis of their oxidative stability is still needed. The present study shows a close analysis of the oxidative stability of the oils obtained from the kernel and pulp of Acrocomia aculeata fruits, evaluating the influence of the intrinsic antioxidants and the fatty acid composition on the oil’s thermal stability. A complete characterization of the physical-chemical and optical properties of the oils was performed. The results showed that 66% of the fatty acids present in the pulp oil are unsaturated, while 75% are saturated in the kernel oil. A higher content of intrinsic antioxidants was obtained in the pulp oil, and an induction period (at 110 °C) of 65 and 43 h was determined for the pulp and kernel oil, respectively. Additionally, oil absorption increases due to the formation of degradation products, and a new fluorescent compound was formed during the oil oxidation process at 110 °C. Even though the pulp presented a high content of unsaturated fatty acids, the pulp oil was more stable than the kernel oil due to its higher content of intrinsic antioxidant, especially carotenoids. The results also demonstrated that oil oxidation can be optically determined by analyzing the absorption at 232 and 270 nm, as well as the emission at 424 nm. Full article

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13 pages, 5411 KiB

Open AccessArticle

Statistical Model and Performance Analysis of a Novel Multilevel Polarization Modulation in Local “Twisted” Fibers

by Pierluigi Perrone^*, Silvello Betti and Giuseppe Giulio Rutigliano

Department of Electronics Engineering, University of Rome “Tor Vergata”, Via del Politecnico 1, 00133 Rome, Italy

Photonics 2017, 4(1), 5; https://doi.org/10.3390/photonics4010005 - 26 Jan 2017

Cited by 2 | Viewed by 4549

Abstract

Transmission demand continues to grow and higher capacity optical communication systems are required to economically meet this ever-increasing need for communication services. This article expands and deepens the study of a novel optical communication system for high-capacity Local Area Networks (LANs), based on [...] Read more.

Transmission demand continues to grow and higher capacity optical communication systems are required to economically meet this ever-increasing need for communication services. This article expands and deepens the study of a novel optical communication system for high-capacity Local Area Networks (LANs), based on twisted optical fibers. The complete statistical behavior of this system is shown, designed for more efficient use of the fiber single-channel capacity by adopting an unconventional multilevel polarization modulation (called “bands of polarization”). Starting from simulative results, a possible reference mathematical model is proposed. Finally, the system performance is analyzed in the presence of shot-noise (coherent detection) or thermal noise (direct detection). Full article

(This article belongs to the Special Issue Optical Networks for Communications)

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10 pages, 3034 KiB

Open AccessArticle

Element Selective Probe of the Ultra-Fast Magnetic Response to an Element Selective Excitation in Fe-Ni Compounds Using a Two-Color FEL Source

by Eugenio Ferrari^1,2,†, Carlo Spezzani^1,3, Franck Fortuna⁴, Renaud Delaunay⁵

, Franck Vidal⁶, Ivaylo Nikolov¹, Paolo Cinquegrana¹, Bruno Diviacco¹, David Gauthier¹, Giuseppe Penco¹

, Primož Rebernik Ribič¹, Eléonore Roussel¹

, Mauro Trovò¹, Jean-Baptiste Moussy⁷, Tommaso Pincelli⁸, Lounès Lounis^6,9, Cristian Svetina^1,10, Marco Zangrando^1,11

, Nicola Mahne¹, Lorenzo Raimondi¹, Michele Manfredda¹, Emanuele Pedersoli¹

, Flavio Capotondi¹, Alexander Demidovich¹, Luca Giannessi^1,12, Maya Kiskinova¹, Giovanni De Ninno^1,13, Miltcho Boyanov Danailov¹, Enrico Allaria^1,* and Maurizio Sacchi^6,14,*

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¹ ELETTRA—Sincrotrone Trieste, Area Science Park, 34149 Trieste, Italy

² Dipartimento di Fisica, Università degli Studi di Trieste, 34127 Trieste, Italy

³ Laboratoire de Physique des Solides, Université Paris-Sud, CNRS-UMR 8502, Bât. 510, 91405 Orsay, France

⁴ Centre de Sciences Nucléaires et de Sciences de la Matière, Université Paris-Sud, CNRS UMR 8609, Bât. 104-108, 91405 Orsay, France

⁵ Laboratoire de Chimie Physique Matière et Rayonnement, Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7614, 75005 Paris, France

⁶ Institut des NanoSciences de Paris, Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7588, 75005 Paris, France

⁷ Service de Physique de l’Etat Condensé, DSM/IRAMIS/SPEC, CNRS UMR 3680, CEA Saclay, 91191 Gif-sur-Yvette, France

⁸ Dipartimento di Fisica, Università degli Studi di Milano, 20133 Milano, Italy

⁹ Ecole Normale Supérieure, PSL Research University, 75231 Paris, France

¹⁰ Graduate School of Nanotechnology, Università degli Studi di Trieste, 34127 Trieste, Italy

¹¹ Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, 34149 Trieste, Italy

¹² ENEA, Centro Ricerche Frascati, Via E. Fermi 45, 00044 Frascati, Italy

¹³ Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia

¹⁴ Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France

^† Current Address: Particle Accelerator Physics Laboratory, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.

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Photonics 2017, 4(1), 6; https://doi.org/10.3390/photonics4010006 - 26 Jan 2017

Cited by 8 | Viewed by 5609

Abstract

The potential of the two-color mode implemented at the FERMI free-electron laser (FEL) source for pumping and probing selectively different atomic species has been demonstrated by time-resolved scattering experiments with permalloy (FeNi alloy) and NiFe₂O₄ samples. We monitored the ultra-fast [...] Read more.

The potential of the two-color mode implemented at the FERMI free-electron laser (FEL) source for pumping and probing selectively different atomic species has been demonstrated by time-resolved scattering experiments with permalloy (FeNi alloy) and NiFe₂O₄ samples. We monitored the ultra-fast demagnetization of Ni induced by the pump FEL pulse, by tuning the linearly-polarized FEL probe pulse to the Ni-3p resonance and measuring the scattered intensity in the transverse magneto-optical Kerr effect geometry. The measurements were performed by varying the intensity of the FEL pump pulse, tuning its wavelength to and off of the Fe-3p resonance, and by spanning the FEL probe pulse delays across the 300–900 fs range. The obtained results have evidenced that for the case of NiFe₂O₄, there is a sensible difference in the magnetic response at the Ni site when the pump pulse causes electronic excitations at the Fe site. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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10 pages, 2810 KiB

Open AccessArticle

Phase-Insensitive Scattering of Terahertz Radiation

by Mihail Petev^1,2, NiclasWesterberg¹, Eleonora Rubino¹, Daniel Moss^1,3, Arnaud Couairon⁴, François Légaré⁵, Roberto Morandotti^5,6,7

, Daniele Faccio^1,* and Matteo Clerici^8,*

¹ School of Engineering and Physical Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK

² Max Planck Institute for the Science of Light (MPL), D-91058 Erlangen, Germany

³ Department of Physics and Solid State Institute, Technion, Haifa 32000, Israel

⁴ Centre de Physique Théorique CNRS, École Polytechnique, F-91128 Palaiseau, France

⁵ INRS-EMT, 1650 Blvd. Lionel-Boulet, Varennes, QC J3X 1S2, Canada

⁶ Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China

⁷ National Research University of Information Technologies, Mechanics and Optics, St. Petersburg 197101, Russia

⁸ School of Engineering, University of Glasgow, Glasgow G12 8LT, UK

Photonics 2017, 4(1), 7; https://doi.org/10.3390/photonics4010007 - 31 Jan 2017

Cited by 5 | Viewed by 8409

Abstract

The nonlinear interaction between Near-Infrared (NIR) and Terahertz pulses is principally investigated as a means for the detection of radiation in the hardly accessible THz spectral region. Most studies have targeted second-order nonlinear processes, given their higher efficiencies, and only a limited number [...] Read more.

The nonlinear interaction between Near-Infrared (NIR) and Terahertz pulses is principally investigated as a means for the detection of radiation in the hardly accessible THz spectral region. Most studies have targeted second-order nonlinear processes, given their higher efficiencies, and only a limited number have addressed third-order nonlinear interactions, mainly investigating four-wave mixing in air for broadband THz detection. We have studied the nonlinear interaction between THz and NIR pulses in solid-state media (specifically diamond), and we show how the former can be frequency-shifted up to UV frequencies by the scattering from the nonlinear polarisation induced by the latter. Such UV emission differs from the well-known electric field-induced second harmonic (EFISH) one, as it is generated via a phase-insensitive scattering, rather than a sum- or difference-frequency four-wave-mixing process. Full article

(This article belongs to the Special Issue Ultrafast Photonics and Attosecond Sciences)

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11 pages, 3335 KiB

Open AccessArticle

Experimental Demonstration of an Electro-Absorption Modulated Laser for High-Speed Transmissions at 1.55-μm Window Using Digital Signal Processing

by Fotini Karinou^*

, Nebojsa Stojanovic, Cristian Prodaniuc and Qiang Zhang

Huawei Technologies Duesseldorf GmbH, Riestrasse 25, 80992 Munich, Germany

Photonics 2017, 4(1), 9; https://doi.org/10.3390/photonics4010009 - 8 Feb 2017

Cited by 5 | Viewed by 6019

Abstract

We experimentally investigate the transmission performance of 56 Gb/s four-level pulse amplitude modulation (PAM-4) over 30-km standard single mode fiber (SMF) using a C-band EML for low-cost metro and short-reach wavelength division multiplexing (WDM) applications. Bit error rate (BER) performance below the HD-FEC [...] Read more.

We experimentally investigate the transmission performance of 56 Gb/s four-level pulse amplitude modulation (PAM-4) over 30-km standard single mode fiber (SMF) using a C-band EML for low-cost metro and short-reach wavelength division multiplexing (WDM) applications. Bit error rate (BER) performance below the HD-FEC threshold is achieved for up to 30-km maximum reported distance without employing dispersion compensation fiber (DCF) in the link. Full article

(This article belongs to the Special Issue Optical Networks for Communications)

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13 pages, 4462 KiB

Open AccessArticle

Dipole Emission to Surface Plasmon-Coupled Enhanced Transmission in Diamond Substrates with Nitrogen Vacancy Center- Near the Surface

by Amir Djalalian-Assl

School of Physics, The University of Melbourne, Victoria 3010, Australia

Photonics 2017, 4(1), 10; https://doi.org/10.3390/photonics4010010 - 10 Feb 2017

Cited by 4 | Viewed by 6831

Abstract

For distances less 10 nm, a total energy transfer occurs from a quantum emitter to a nearby metallic surface, producing evanescent surface waves that are plasmonic in nature. When investigating a metallic nanohole supported on an optically dense substrate (such as diamond with [...] Read more.

For distances less 10 nm, a total energy transfer occurs from a quantum emitter to a nearby metallic surface, producing evanescent surface waves that are plasmonic in nature. When investigating a metallic nanohole supported on an optically dense substrate (such as diamond with nitrogen vacancy center), the scattering occurred preferentially from the diamond substrate towards the air for dipole distances less 10 nm from the aperture. In addition, an enhancement to the dipole’s radiative decay rate was observed when resonance of the aperture matched the emitters wavelength. The relationship between an emitter and a nearby resonant aperture is shown to be that of the resonance energy transfer where the emitter acts as a donor and the hole as an acceptor. In conjunction with the preferential scattering behavior, this has led to the proposed device that operates in transmission mode, eliminating the need for epi-illumination techniques and optically denser than air superstrates in the collection cycle, hence making the design simpler and more suitable for miniaturization. A design criterion for the surface grating is also proposed to improve the performance, where the period of the grating differs significantly from the wavelength of the surface plasmon polaritons. Response of the proposed device is further studied with respect to changes in nitrogen vacancy’s position and its dipolar orientation to identify the crystallographic planes of diamond over which the performance of the device is maximized. Full article

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14 pages, 10899 KiB

Open AccessArticle

Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

by Christian Kijatkin¹, Juliane Eggert¹, Sergej Bock^1,2, Dirk Berben², Laura Oláh³, Zsuzsanna Szaller³

, Zsolt Kis³ and Mirco Imlau^1,*

¹ School of Physics, Osnabrueck University, Barbarastr. 7, 49076 Osnabrueck, Germany

² Department of Electrical Engineering and Information Technology, South Westphalia University of Applied Sciences, Haldener Str. 182, 58095 Hagen, Germany

³ Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Konkoly-Thege u. 29-33, 1121 Budapest, Hungary

Photonics 2017, 4(1), 11; https://doi.org/10.3390/photonics4010011 - 19 Feb 2017

Cited by 19 | Viewed by 6958

Abstract

Nonlinear diffuse femtosecond-pulse reflectometry is introduced as a powerful experimental tool for the unambiguous characterization of polar and non-polar point symmetry groups of harmonic upconversion nanoparticles. Using intense ultrashort 40 femtosecond laser pulses and an appropriate figure of merit (FOM), second and third [...] Read more.

Nonlinear diffuse femtosecond-pulse reflectometry is introduced as a powerful experimental tool for the unambiguous characterization of polar and non-polar point symmetry groups of harmonic upconversion nanoparticles. Using intense ultrashort 40 femtosecond laser pulses and an appropriate figure of merit (FOM), second and third harmonic emission serve for the structural characterization of polar Yb-doped lithium niobate and non-polar titanium dioxide nanoparticles. The tool is capable of differentiating these two samples by FOM values that differ by up to 13 orders of magnitude. The general applicability to harmonic upconversion nanoparticles over a broad range of intensities and wavelength spectrum, is discussed. Full article

(This article belongs to the Special Issue Ultrafast Photonics and Attosecond Sciences)

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13 pages, 4095 KiB

Open AccessArticle

Novel Equalization Techniques for Space Division Multiplexing Based on Stokes Space Update Rule

by Francisco Javier Vaquero Caballero^1,*, Fabio Pittalà¹, Gernot Goeger¹, Mi Wang¹, Yabin Ye¹ and Idelfonso Tafur Monroy²

¹ ERC, Huawei Technologies Duesseldorf GmbH, Riesstrasse 25, D-80992 Munich, Germany

² Technical University of Denmark (DTU), Ørsteds Plads, Build. 358, 2800 Kgs. Lyngby, Denmark

Photonics 2017, 4(1), 12; https://doi.org/10.3390/photonics4010012 - 20 Feb 2017

Cited by 6 | Viewed by 5403

Abstract

Space division multiplexing (SDM) is a promising technology that aims to overcome the capacity crunch of optical communications. In this paper, we introduce the multiple-input multiple-output (MIMO) Stokes Space Algorithm (SSA) implemented in frequency domain, a novel equalization technique for space division multiplexing [...] Read more.

Space division multiplexing (SDM) is a promising technology that aims to overcome the capacity crunch of optical communications. In this paper, we introduce the multiple-input multiple-output (MIMO) Stokes Space Algorithm (SSA) implemented in frequency domain, a novel equalization technique for space division multiplexing (SDM). Although different papers have been published about the SSA and its MIMO implementation, we provide for the first time an analysis of the of the convergence speed and frequency offset of the SSA compared to the least mean square (LMS). SSA algorithm can deal with higher frequency offsets and linewidths than LMS, being suitable for optical communications with higher phase noise. SSA does not need pre-compensation of frequency offset, which can be compensated after equalization without penalties. On the other hand, due to reduced convergence speed, SSA requires longer training sequences than LMS. Full article

(This article belongs to the Special Issue Optical Networks for Communications)

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15 pages, 4684 KiB

Open AccessArticle

High-Speed, High-Performance DQPSK Optical Links with Reduced Complexity VDFE Equalizers

by Maki Nanou^*, Christina (Tanya) Politi, Alexandros Stavdas, Kristina Georgoulakis and George-Othon Glentis

University of Peloponnese, Department of Informatics and Telecommunications, Tripolis, Terma Karaiskaki 22100, Greece

Photonics 2017, 4(1), 13; https://doi.org/10.3390/photonics4010013 - 26 Feb 2017

Cited by 2 | Viewed by 4563

Abstract

Optical transmission technologies optimized for optical network segments sensitive to power consumption and cost, comprise modulation formats with direct detection technologies. Specifically, non-return to zero differential quaternary phase shift keying (NRZ-DQPSK) in deployed fiber plants, combined with high-performance, low-complexity electronic equalizers to compensate [...] Read more.

Optical transmission technologies optimized for optical network segments sensitive to power consumption and cost, comprise modulation formats with direct detection technologies. Specifically, non-return to zero differential quaternary phase shift keying (NRZ-DQPSK) in deployed fiber plants, combined with high-performance, low-complexity electronic equalizers to compensate residual impairments at the receiver end, can be proved as a viable solution for high-performance, high-capacity optical links. Joint processing of the constructive and the destructive signals at the single-ended DQPSK receiver provides improved performance compared to the balanced configuration, however, at the expense of higher hardware requirements, a fact that may not be neglected especially in the case of high-speed optical links. To overcome this bottleneck, the use of partially joint constructive/destructive DQPSK equalization is investigated in this paper. Symbol-by-symbol equalization is performed by means of Volterra decision feedback-type equalizers, driven by a reduced subset of signals selected from the constructive and the destructive ports of the optical detectors. The proposed approach offers a low-complexity alternative for electronic equalization, without sacrificing much of the performance compared to the fully-deployed counterpart. The efficiency of the proposed equalizers is demonstrated by means of computer simulation in a typical optical transmission scenario. Full article

(This article belongs to the Special Issue Optical Networks for Communications)

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11 pages, 1906 KiB

Open AccessArticle

Design Study of Time-Preserving Grating Monochromators for Ultrashort Pulses in the Extreme-Ultraviolet and Soft X-Rays

by Fabio Frassetto¹, Nicola Fabris^1,2, Paolo Miotti^1,2

and Luca Poletto^1,*

¹ Institute of Photonics and Nanotechnologies, National Research Council of Italy, via Trasea 7, I-35131 Padova, Italy

² Department of Information Engineering, University of Padova, via Gradenigo 6/B, I-35131 Padova, Italy

Photonics 2017, 4(1), 14; https://doi.org/10.3390/photonics4010014 - 1 Mar 2017

Cited by 10 | Viewed by 5143

Abstract

The design of grating-based instruments to handle and condition coherent ultrafast pulses in the extreme-ultraviolet is discussed. The main application of such instruments is the monochromatization of high-order laser harmonics and free-electron-laser pulses in the femtosecond time scale. Broad-band monochromators require the use [...] Read more.

The design of grating-based instruments to handle and condition coherent ultrafast pulses in the extreme-ultraviolet is discussed. The main application of such instruments is the monochromatization of high-order laser harmonics and free-electron-laser pulses in the femtosecond time scale. Broad-band monochromators require the use of diffraction gratings at grazing incidence. A grating can be used for the spectral selection of ultrashort pulses without altering the pulse duration in a significant way, provided that the number of illuminated grooves is equal to the resolution. We discuss here the design conditions to be fulfilled by a grating monochromator that does not increase the pulse duration significantly longer than the Fourier limit. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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15 pages, 911 KiB

Open AccessArticle

Optical Klystron Enhancement to Self Ampliﬁed Spontaneous Emission at FERMI

by Giuseppe Penco^1,*

, Enrico Allaria¹, Giovanni De Ninno^1,2, Eugenio Ferrari^1,3, Luca Giannessi^1,4

, Eléonore Roussel¹

and Simone Spampinati¹

¹ Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14-km 163.5 in AREA Science Park, Basovizza, 34149 Trieste, Italy

² Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia

³ Paul Scherrer Institut, 5232 Villigen, Switzerland

⁴ Enea, via Enrico Fermi 45, Frascati, 00044 Roma, Italy

Photonics 2017, 4(1), 15; https://doi.org/10.3390/photonics4010015 - 1 Mar 2017

Cited by 17 | Viewed by 5032

Abstract

The optical klystron enhancement to a self-ampliﬁed spontaneous emission free electron laser has been studied in theory and in simulations and has been experimentally demonstrated on a single-pass high-gain free electron laser, the FERMI FEL-1, in 2014. The main concept consists of two [...] Read more.

The optical klystron enhancement to a self-ampliﬁed spontaneous emission free electron laser has been studied in theory and in simulations and has been experimentally demonstrated on a single-pass high-gain free electron laser, the FERMI FEL-1, in 2014. The main concept consists of two undulators separated by a dispersive section that converts the energy modulation induced in the ﬁrst undulator in density modulation, enhancing the coherent harmonic generation in the ﬁrst part of the second undulator. This scheme could be replicated in a multi-stage: the bunching is enhanced after each dispersive section, consistently reducing the saturation length. We have applied the multi-stage optical klystron (OK) scheme on the FEL-2 line at FERMI, whose layout includes three dispersive sections. Optimizing the strength of the dispersions allowed a signiﬁcant increase of the self-ampliﬁed spontaneous emission (SASE) intensity in comparison to a single-stage OK and extending to the soft-X rays the OK enhanced SASE previously demonstrated on FEL-1. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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8 pages, 2953 KiB

Open AccessArticle

Experimental Evaluation of Impairments in Unrepeatered DP-16QAM Link with Distributed Raman Amplification

by Xiaodan Pang^1,2

, Oskars Ozolins¹

, Atalla El-Taher^3,*

, Richard Schatz², Gunnar Jacobsen¹, Sergey Sergeyev³ and Sergei Popov²

¹ Networking and Transmission Laboratory, Acreo Swedish ICT AB, Kista SE-16425, Sweden

² Optics and Photonics Division, Royal Institute of Technology (KTH), Kista SE-16440, Sweden

³ Aston Institute of Photonic Technologies, Aston University, Birmingham B4 7ET, UK

Photonics 2017, 4(1), 16; https://doi.org/10.3390/photonics4010016 - 8 Mar 2017

Cited by 1 | Viewed by 4926

Abstract

The transmission impairments of a Raman amplified link using dual-polarization 16-quadrature amplitude modulation (DP-16QAM) are experimentally characterized. The impact of amplitude and phase noise on the signal due to relative intensity noise (RIN) transfer from the pump are compared for two pumping configurations: [...] Read more.

The transmission impairments of a Raman amplified link using dual-polarization 16-quadrature amplitude modulation (DP-16QAM) are experimentally characterized. The impact of amplitude and phase noise on the signal due to relative intensity noise (RIN) transfer from the pump are compared for two pumping configurations: first-order backward pumping and bi-directional pumping. Experimental results indicate that with increased Raman backward pump power, though the optical signal-to-noise ratio (OSNR) is increased, so is the pump-induced amplitude and phase noise. The transmission performance is firstly improved by the enhanced OSNR at a low pump power until an optimum point is reached, and then the impairments due to pump-induced noise start to dominate. However, the introduction of a low pump power in the forward direction can further improve the system’s performance. Full article

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13 pages, 2302 KiB

Open AccessArticle

XUV Transient Absorption Spectroscopy: Probing Laser-Perturbed Dipole Polarization in Single Atom, Macroscopic, and Molecular Regimes

by Chen-Ting Liao^1,2

and Arvinder Sandhu^1,2,*

¹ College of Optical Sciences, University of Arizona, Tucson, AZ 85721, USA

² Department of Physics, University of Arizona, Tucson, AZ 85721, USA

Photonics 2017, 4(1), 17; https://doi.org/10.3390/photonics4010017 - 8 Mar 2017

Cited by 7 | Viewed by 9538

Abstract

We employ an extreme ultraviolet (XUV) pulse to impulsively excite dipole polarization in atoms or molecules, which corresponds to coherently prepared superposition of excited states. A delayed near infrared (NIR) pulse then perturbs the fast evolving polarization, and the resultant absorbance change is [...] Read more.

We employ an extreme ultraviolet (XUV) pulse to impulsively excite dipole polarization in atoms or molecules, which corresponds to coherently prepared superposition of excited states. A delayed near infrared (NIR) pulse then perturbs the fast evolving polarization, and the resultant absorbance change is monitored in dilute helium, dense helium, and sulfur hexaﬂuoride (SF6) molecules. We observe and quantify the time-dependence of various transient phenomena in helium atoms,includinglaser-inducedphase(LIP),time-varying(AC)Starkshift,quantumpathinterference, and laser-induced continuum structure. In the case of dense helium targets, we discuss nonlinear macroscopic propagation effects pertaining to LIP and resonant pulse propagation, which accoun tfor the appearance of new spectral features in transient lineshapes. We then use tunable NIR photons to demonstrate the wavelength dependence of the transient laser induced effects. In the case of molecular polarization experiment in SF6, we show suppression of XUV photoabsorption corresponding to inter-valence transitions in the presence of a strong NIR ﬁeld. In each case, the temporal evolution of transient absorption spectra allows us to observe and understand the transient laser induced modiﬁcations of the electronic structure of atoms and molecules. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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11 pages, 2316 KiB

Open AccessArticle

A Highly Sensitive Gold-Coated Photonic Crystal Fiber Biosensor Based on Surface Plasmon Resonance

by Md. Rabiul Hasan^1,*, Sanjida Akter¹, Ahmmed A. Rifat², Sohel Rana³ and Sharafat Ali⁴

¹ Department of Electronics & Telecommunication Engineering, Rajshahi University of Engineering & Technology, Rajshahi 6204, Bangladesh

² Integrated Lightwave Research Group, Department of Electrical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

³ Department of Electrical & Electronic Engineering, Rajshahi University of Engineering & Technology, Rajshahi 6204, Bangladesh

⁴ School of Computer and Communication Engineering, Center of Excellence, Advanced Communication Engineering Cluster, Pauh Putra Campus, Arau 02600, Perlis, Malaysia

Photonics 2017, 4(1), 18; https://doi.org/10.3390/photonics4010018 - 10 Mar 2017

Cited by 175 | Viewed by 11305

Abstract

In this paper, we numerically demonstrate a two-layer circular lattice photonic crystal fiber (PCF) biosensor based on the principle of surface plasmon resonance (SPR). The finite element method (FEM) with circular perfectly matched layer (PML) boundary condition is applied to evaluate the performance [...] Read more.

In this paper, we numerically demonstrate a two-layer circular lattice photonic crystal fiber (PCF) biosensor based on the principle of surface plasmon resonance (SPR). The finite element method (FEM) with circular perfectly matched layer (PML) boundary condition is applied to evaluate the performance of the proposed sensor. A thin gold layer is deposited outside the PCF structure, which acts as the plasmonic material for this design. The sensing layer (analyte) is implemented in the outermost layer, which permits easy and more practical fabrication process compared to analyte is put inside the air holes. It is demonstrated that, at gold layer thickness of 40 nm, the proposed sensor shows maximum sensitivity of 2200 nm/RIU using the wavelength interrogation method in the sensing range between 1.33–1.36. Besides, using an amplitude interrogation method, a maximum sensitivity of 266 RIU⁻¹ and a maximum sensor resolution of 3.75 × 10⁻⁵ RIU are obtained. We also discuss how phase matching points are varied with different fiber parameters. Owing to high sensitivity and simple design, the proposed sensor may find important applications in biochemical and biological analyte detection. Full article

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14 pages, 2094 KiB

Open AccessArticle

Echo-Enabled Harmonic Generation Studies for the FERMI Free-Electron Laser

by Primož Rebernik Ribič^1,*, Eléonore Roussel¹, Gregory Penn², Giovanni De Ninno^1,3, Luca Giannessi¹

, Giuseppe Penco¹ and Enrico Allaria¹

¹ Elettra-Sincrotrone Trieste, Strada Statale 14-km 163,5, 34149 Basovizza, Trieste, Italy

² Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA

³ Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia

Photonics 2017, 4(1), 19; https://doi.org/10.3390/photonics4010019 - 14 Mar 2017

Cited by 23 | Viewed by 6982

Abstract

Studying ultrafast processes on the nanoscale with element specificity requires a powerful femtosecond source of tunable extreme-ultraviolet (XUV) or x-ray radiation, such as a free-electron laser (FEL). Current efforts in FEL development are aimed at improving the wavelength tunability and multicolor operation, which [...] Read more.

Studying ultrafast processes on the nanoscale with element specificity requires a powerful femtosecond source of tunable extreme-ultraviolet (XUV) or x-ray radiation, such as a free-electron laser (FEL). Current efforts in FEL development are aimed at improving the wavelength tunability and multicolor operation, which will potentially lead to the development of new characterization techniques offering a higher chemical sensitivity and improved spatial resolution. One of the most promising approaches is the echo-enabled harmonic generation (EEHG), where two external seed lasers are used to precisely control the spectro-temporal properties of the FEL pulse. Here, we study the expected performance of EEHG at the FERMI FEL, using numerical simulations. We show that, by employing the existing FERMI layout with minor modifications, the EEHG scheme will be able to produce gigawatt peak-power pulses at wavelengths as short as 5 nm. We discuss some possible detrimental effects that may affect the performance of EEHG and compare the results to the existing double-stage FEL cascade, currently in operation at FERMI. Finally, our simulations show that, after substantial machine upgrades, EEHG has the potential to deliver coherent multicolor pulses reaching wavelengths as short as 3 nm, enabling x-ray pump–x-ray probe experiments in the water window. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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Review

Jump to: Editorial, Research

27 pages, 5862 KiB

Open AccessReview

Future Scenarios for Software-Defined Metro and Access Networks and Software-Defined Photonics

by Tommaso Muciaccia

and Vittorio M. N. Passaro^*

Photonics Research Group, Department of Electrical and Information Engineering, Politecnico di Bari, via Edoardo Orabona n. 4, 70125 Bari, Italy

Photonics 2017, 4(1), 1; https://doi.org/10.3390/photonics4010001 - 3 Jan 2017

Cited by 19 | Viewed by 11601

Abstract

In recent years, architectures, devices, and components in telecommunication networks have been challenged by evolutionary and revolutionary factors which are drastically changing the traffic features. Most of these changes imply the need for major re-configurability and programmability not only in data-centers and core [...] Read more.

In recent years, architectures, devices, and components in telecommunication networks have been challenged by evolutionary and revolutionary factors which are drastically changing the traffic features. Most of these changes imply the need for major re-configurability and programmability not only in data-centers and core networks, but also in the metro-access segment. In a wide variety of contexts, this necessity has been addressed by the proposed introduction of the innovative paradigm of software-defined networks (SDNs). Several solutions inspired by the SDN model have been recently proposed also for metro and access networks, where the adoption of a new generation of software-defined reconfigurable integrated photonic devices is highly desirable. In this paper, we review the possible future application scenarios for software-defined metro and access networks and software-defined photonics (SDP), on the base of analytics, statistics, and surveys. This work describes the reasons underpinning the presented radical change of paradigm and summarizes the most significant solutions proposed in literature, with a specific emphasis to physical-layer reconfigurable networks and a focus on both architectures and devices. Full article

(This article belongs to the Special Issue Optical Networks for Communications)

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26 pages, 5614 KiB

Open AccessReview

Ultrafast Laser Pulses for Structuring Materials at Micro/Nano Scale: From Waveguides to Superhydrophobic Surfaces

by Daniel S. Correa^1,*

, Juliana M. P. Almeida², Gustavo F. B. Almeida², Marcos R. Cardoso², Leonardo De Boni² and Cleber R. Mendonça^2,*

¹ National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentação (CNPDIA), 13560-970 São Carlos, SP, Brazil

² Carlos Institute of Physics, University of São Paulo, PO Box 369, 13560-970 São Carlos, SP, Brazil

Photonics 2017, 4(1), 8; https://doi.org/10.3390/photonics4010008 - 31 Jan 2017

Cited by 36 | Viewed by 10183

Abstract

The current demand for fabricating optical and photonic devices displaying high performance, using low-cost and time-saving methods, prompts femtosecond (fs)-laser processing as a promising methodology. High and low repetition femtosecond lasers enable surface and/or bulk modification of distinct materials, which can be used [...] Read more.

The current demand for fabricating optical and photonic devices displaying high performance, using low-cost and time-saving methods, prompts femtosecond (fs)-laser processing as a promising methodology. High and low repetition femtosecond lasers enable surface and/or bulk modification of distinct materials, which can be used for applications ranging from optical waveguides to superhydrophobic surfaces. Herein, some fundamental aspects of fs-laser processing of materials, as well as the basics of their most common experimental apparatuses, are introduced. A survey of results on polymer fs-laser processing, resulting in 3D waveguides, electroluminescent structures and active hybrid-microstructures for luminescence or biological microenvironments is presented. Similarly, results of fs-laser processing on glasses, gold and silicon to produce waveguides containing metallic nanoparticles, analytical chemical sensors and surface with modified features, respectively, are also described. The complexity of fs-laser micromachining involves precise control of material properties, pushing ultrafast laser processing as an advanced technique for micro/nano devices. Full article

(This article belongs to the Special Issue Ultrafast Photonics and Attosecond Sciences)

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