Prof. Mourad Zghal Profile

Prof. Mourad Zghal

Head of R&I at Ecole d'Ingenieurs

SPIE Involvement:

Author | Editor

Area of Expertise:

Nonlinear optics , Ultrafast optics , Speciality fibers , Supecontinuum generation , History of Science

Websites:

Company Website | Personal Website

Dr. Mourad ZGHAL is actually Professor at the University of Carthage, Tunisia. He received his Ph.D in electrical engineering from Tunis El-Manar University in 2000. His scientific activities are mainly focused on integrated optical devices, design and characterization of photonic crystal fibers, and nonlinear propagation of ultrashort pulses. He served at numerous program or steering committee of international scientific conferences. He was co-chair of the 2013 edition of the ETOP (Education and Training in Optics and Photonics) conference. In addition to his research activities, Prof ZGHAL has been extremely active in promoting photonics in Tunisia and Africa. He is the co-founder in 2002 and president since 2012 of the Optical Society of Tunisia. He also co-founded the African Laser Center, an organization encouraging exchange of researchers and students across Africa. He was elected as Vice President of the ICO International Commission for Optics (2014-2017). Prof Zghal received several major awards including the 2008 ICO/ICTP Gallieno Denardo prize for “his original work in the development of numerical modelling techniques for photonic crystal fibres, and for his active commitment aimed at the diffusion of research in optics in Africa”. Prof Zghal is an elected fellow of OSA and SPIE.

Proceedings Article | 14 September 2018 Open Access

Hands-on experimental and computer laboratory in optics: the Young double slit experiment

H. Ghalila, A. Ammar, Y. Majdi, S. Lahmar, Z. Dhaouadi, M. Zghal, Zohra Ben Lakhdara, V. Lakshminarayanan

Proceedings Volume 10741, 107410F (2018) https://doi.org/10.1117/12.2322164

KEYWORDS: Diffraction, Numerical modeling, Computer programming, Optical simulations, Active optics, Physics, Cameras, Photography, Image processing, Communication engineering

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Proceedings Article | 16 August 2017 Open Access

Optics simulations: a Python workshop

H. Ghalila, A. Ammar, S. Varadharajan, Y. Majdi, M. Zghal, S. Lahmar, V. Lakshminarayanan

Proceedings Volume 10452, 1045218 (2017) https://doi.org/10.1117/12.2268377

KEYWORDS: Computer simulations, Numerical simulations, Optical simulations, Computer programming languages, Computer programming, Numerical analysis, Physics, Computing systems

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Proceedings Article | 27 September 2016 Presentation + Paper

Optical communications beyond orbital angular momentum

Carmelo Rosales-Guzmán, Abderrahmen Trichili, Angela Dudley, Bienvenu Ndagano, Amine Ben Salem, Mourad Zghal, Andrew Forbes

Proceedings Volume 9950, 99500C (2016) https://doi.org/10.1117/12.2238416

KEYWORDS: Optical communications, Free space, Telecommunications, Signal detection, Computer programming, Multiplexing, Holograms, Spatial light modulators, RGB color model, Digital holography

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Proceedings Article | 15 September 2016 Open Access

Stimulated Brillouin scattering in highly birefringent multimode tapered chalcogenide photonic crystal fiber for distributed optical sensors (Retraction Notice)

Amira Baili, Rim Cherif, Mourad Zghal

Proceedings Volume 9927, 992717 (2016) https://doi.org/10.1117/12.2238068

KEYWORDS: Scattering, Photonic crystal fibers, Optical sensors, Chalcogenides, Laser scattering, Nanoengineering, Nanolithography, Multimode fibers, Fiber lasers, Quantum electronics

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Proceedings Article | 7 September 2016 Presentation + Paper

Rigorous study of supercontinuum generation by high-order optical modes

Amine Ben Salem, Abderrahmen Trichili, Rim Cherif, Mourad Zghal

Proceedings Volume 9958, 99580L (2016) https://doi.org/10.1117/12.2237173

KEYWORDS: Photonic crystal fibers, Supercontinuum generation, Energy transfer, Photonic crystals, Dispersion, Solitons, Wave propagation, Nonlinear optics, Modulation, Four wave mixing

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Proceedings Article | 7 September 2016 Open Access

Multimode Brillouin spectrum in dual core chalcogenide photonic nanofiber for sensing applications (Withdrawal Notice)

Amira Baili, Rim Cherif, Mourad Zghal

Proceedings Volume 9958, 995806 (2016) https://doi.org/10.1117/12.2237202

KEYWORDS: Chalcogenides, Photonic crystal fibers, Photonic nanostructures, Nanofibers, Photodetectors, Crystals, Photonic crystal devices, Photonic crystals, Nanoengineering, Current controlled current source

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Proceedings Article | 7 September 2016 Presentation + Paper

Mid-infrared supercontinuum generation in multimode step index chalcogenide fiber

Ameni Ben Khalifa, Amine Ben Salem, Rim Cherif, Mourad Zghal

Proceedings Volume 9958, 99580M (2016) https://doi.org/10.1117/12.2237841

KEYWORDS: Mid-IR, Chalcogenides, Multimode fibers, Supercontinuum generation, Step index fibers, Cladding, Glasses, Wave propagation, Dispersion, Energy transfer

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SPIE Journal Paper | 10 June 2016

Ultraflat-top midinfrared coherent broadband supercontinuum using all normal A_s2S₅-borosilicate hybrid photonic crystal fiber

Amine Ben Salem, Mbaye Diouf, Rim Cherif, Ahmadou Wague, Mourad Zghal

OE, Vol. 55, Issue 06, 066109, (June 2016) https://doi.org/10.1117/12.10.1117/1.OE.55.6.066109

KEYWORDS: Mid-IR, Dispersion, Photonic crystal fibers, Chalcogenides, Optical coherence tomography, Scanning probe microscopy, Borosilicate glass, Structured optical fibers, Light sources, Glasses

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Proceedings Article | 27 April 2016 Paper

Propagation in few modes fiber with strongly coupled groups of modes

Ameni Ben Khalifa, Rim Cherif, Amine Ben Salem, Mourad Zghal

Proceedings Volume 9886, 98860D (2016) https://doi.org/10.1117/12.2227593

KEYWORDS: Multiplexing, Solitons, Multimode fibers, Picosecond phenomena, Dispersion, Cladding, Step index fibers, Phase modulation, Scanning probe microscopy

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Proceedings Article | 26 August 2015 Paper

Slow light generated via Brillouin scattering in small core chalcogenide photonic crystal fiber

A. Baili, R. Cherif, A. Ben Salem, A. Kumar, R. K. Sinha, M. Zghal

Proceedings Volume 9586, 95860P (2015) https://doi.org/10.1117/12.2188418

KEYWORDS: Acoustics, Slow light, Chalcogenides, Light scattering, Scattering, Photonic crystal fibers, Optical fibers, Optical communications, Single mode fibers, Refractive index

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Proceedings Article | 26 August 2015 Paper

A novel As2S5-tellurite hybrid photonic crystal fiber for long mid-IR supercontinuum fiber lasers

Mbaye Diouf, Amine Ben Salem, Rim Cherif, Ahmadou Wague, Mourad Zghal

Proceedings Volume 9586, 95860D (2015) https://doi.org/10.1117/12.2187491

KEYWORDS: Mid-IR, Dispersion, Photonic crystal fibers, Fiber lasers, Glasses, Chalcogenides, Optical parametric oscillators, Refractive index, Raman spectroscopy, Cladding

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Proceedings Article | 26 August 2015 Paper

Design and analysis of rectangular core photonic crystal fiber for supercontinuum generation

Than Singh Saini, Ajeet Kumar, Rim Cherif, R. Sinha, Mourad Zghal

Proceedings Volume 9586, 95860G (2015) https://doi.org/10.1117/12.2187884

KEYWORDS: Dispersion, Photonic crystal fibers, Supercontinuum generation, Mid-IR, Glasses, Femtosecond phenomena, Fiber optic communications, Optical communications, Communication engineering, Telecommunications

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Proceedings Article | 25 August 2015 Paper

Encoding information using Laguerre Gaussian modes

Abderrahmen Trichili, Angela Dudley, Amine Ben Salem, Bienvenu Ndagano, Mourad Zghal, Andrew Forbes

Proceedings Volume 9581, 95810F (2015) https://doi.org/10.1117/12.2189814

KEYWORDS: Computer programming, Free space, Digital holography, Holograms, RGB color model, Receivers, Multiplexing, Spatial light modulators, Free space optics, Signal detection

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SPIE Journal Paper | 21 August 2015

Two octaves spanning supercontinuum in highly nonlinear As₂Se₃ nanophotonic crystal fiber for midinfrared applications

Amira Baili, Rim Cherif, Mourad Zghal

JNP, Vol. 9, Issue 01, 093059, (August 2015) https://doi.org/10.1117/12.10.1117/1.JNP.9.093059

KEYWORDS: Dispersion, Selenium, Supercontinuum generation, Mid-IR, Nonlinear crystals, Nanophotonics, Crystals, Femtosecond phenomena, Scanning probe microscopy, Picosecond phenomena

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SPIE Journal Paper | 7 July 2015

Design of small core tellurite photonic crystal fiber for slow-light-based application using stimulated Brillouin scattering

Rim Cherif, Amine Ben Salem, Than Singh Saini, Ajeet Kumar, Ravindra Sinha, Mourad Zghal

OE, Vol. 54, Issue 07, 075101, (July 2015) https://doi.org/10.1117/12.10.1117/1.OE.54.7.075101

KEYWORDS: Acoustics, Photonic crystal fibers, Slow light, Scattering, Scanning electron microscopy, Refractive index, Telecommunications, Electron microscopes, Glasses, Optical engineering

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Stimulated Brillouin scattering (SBS) performances of small core tellurite photonic crystal fibers (PCF) are rigorously studied. We propose a design of tellurite PCF that is used for slow-light-based applications. We developed a two-dimensional finite element mode solver to numerically study the acoustic and optical properties of complex refractive index profiles including tellurite PCF. Our results include the calculation of Brillouin gain spectrum, Brillouin gain coefficient (gB) and Brillouin frequency shift by taking into account the contribution of the higher-order acoustic modes. Several simulations were run by varying the air-filling ratio of various PCF structures to enhance the SBS. The real scanning electron microscope image of a small core of highly nonlinear tellurite fiber is considered. Optimized results show a frequency shift of 8.43 GHz and a Brillouin gain of 9.48×10−11 m/W with a time delay between 21 and 140 ns. Such fibers have drawn much interest because of their capacity for increasing and tailoring the SBS gain.

Proceedings Article | 27 February 2015

Enhanced stimulated Brillouin scattering in chalcogenide elliptical photonic crystal fibres

I. Abidi, R. Cherif, M. Zghal

Proceedings Volume 9347, 934719 (2015) https://doi.org/10.1117/12.2080237

KEYWORDS: Acoustics, Photonic crystals, Birefringence, Chalcogenides, Scattering, Cladding, Photonic crystal fibers, Modal analysis, Refractive index, Communication engineering

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We show that the stimulated Brillouin scattering (SBS) is enhanced in photonic crystal fibres (PCF) with elliptical air holes characterized by air hole ellipticity η which is the ratio of major to minor axis of the elliptical hole. The study of SBS in elliptical photonic crystal fibres (EPCF) is based on a full modal analysis of the optical and acoustic properties using the finite element method. We investigate the influence of the shape of the air holes on Brillouin gain (gB) spectrum. We find that the interaction between optical and acoustic modes is enhanced in EPCF with a multi-peak behavior of the Brillouin gain spectrum. We also find that by squeezing the lattice of the air holes, the interaction between optical and acoustic waves is enhanced and the gB coefficient is increased.

Proceedings Article | 2 October 2014

Laguerre Gaussian beam multiplexing through turbulence

Abderrahmen Trichili, Thandeka Mhlanga, Darryl Naidoo, Angela Dudley, Mourad Zghal, Andrew Forbes

Proceedings Volume 9194, 91941A (2014) https://doi.org/10.1117/12.2062217

KEYWORDS: Multiplexing, Turbulence, Digital holography, Atmospheric turbulence, Holograms, Electroluminescent displays, Gaussian beams, Optical communications, Superposition, CCD cameras

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We analyze the effect of atmospheric turbulence on the propagation of multiplexed Laguerre Gaussian modes. We present a method to multiplex Laguerre Gaussian modes using digital holograms and decompose the resulting field after encountering a laboratory simulated atmospheric turbulence. The proposed technique makes use of a single spatial light modulator for the generation of superimposed beam and a second spatial light modulator and a CCD camera for the modal decomposition. The obtained results demonstrate how sensitive the Laguerre Gaussian beams are to atmospheric distortions.

Proceedings Article | 2 October 2014

Digital holograms for laser mode multiplexing

Thandeka Mhlanga, Abderrahmen Trichili, Angela Dudley, Darryl Naidoo, Mourad Zghal, Andrew Forbes

Proceedings Volume 9194, 91941B (2014) https://doi.org/10.1117/12.2062999

KEYWORDS: Holograms, Digital holography, Multiplexing, Wavefronts, Spatial light modulators, Modes of laser operation, Optical communications, Data transmission, Single mode fibers, Signal detection

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High-capacity data transmission has been implemented using single channel optical systems. This technique is limited and soon it will be unable to fulﬁll the growing needs for higher bit rate data transmission. Hence multi-mode transmission has been recently given attention as a potential solution to the current problems. In this context, we demonstrate a method of multiplexing laser modes using spatial light modulators (SLMs). In our proposed technique, we use Laguerre Gaussian (LG) modes, which form a complete basis set; hence multi-mode masks can be created by taking a linear combination of the LG modes. Since LG modes are characterised by two degrees of freedom, the azimuthal index ` and radial index ρ, this allows for multi-dimensional states. There are however some experimental challenges which include the sensitivity of the setup to misalignment, that leads to mode-coupling. It is also important that the injected modes ha a uniform power spectrum so that are weighted equally. The size of the multi-modes is highly dependent on the resolution of the SLM.

Proceedings Article | 25 September 2014

Detecting Bessel beams

Abderrahmen Trichili, Thandeka Mhlanga, Yaseera Ismail, Filippus Roux, Melanie McLaren, Mourad Zghal, Andrew Forbes

Proceedings Volume 9194, 91940B (2014) https://doi.org/10.1117/12.2061372

KEYWORDS: Bessel beams, Axicons, Gaussian beams, Digital holography, Holograms, Wave propagation, Beam propagation method, Spatial light modulators, Digital signal processing, Signal detection

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We propose a 2-dimensional method for Bessel Gaussian beam azimuthal and radial decomposition using digital holograms. We illustrate the reconstruction of a Bessel Gaussian beam after encountering an obstruction. From the measured decomposition we show the reconstruction of the amplitude, phase and azimuthal index of the field with high degree of accuracy.

Proceedings Article | 15 September 2014

ETOP: the reference conference in education and training in optics and photonics: an overview of the 12th edition

Manuel F. Costa, Mourad Zghal, Zohra Ben Lakhdar, Vasudevan Lakshminarayanan

Proceedings Volume 9188, 918802 (2014) https://doi.org/10.1117/12.2061211

KEYWORDS: Photonics, Education and training, Laser phosphor displays, Electroluminescence, Optics education, Laser optics, Laser applications, Bridges, Atmospheric optics, Active optics

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Investment in laser technology has led to significant advances in remote sensing, astronomy, industrial processing, and medical technology. To celebrate this rich heritage and promote public awareness in optics and photonics, the SPIE Student Chapter at the Air Force Institute of Technology (AFIT) developed the Laser Propagation Demonstration (LPD). This interactive demonstration serves as one of AFIT’s legacy outreach projects for events involving education in science, technology, engineering, and mathematics (STEM). Initially developed with funding from a LaserFest grant awarded by SPIE in 2010, the goal was to develop a simple hands-on demonstration to highlight the optical effects of diffraction, refraction, and attenuation on laser propagation. Since then, the LPD has undergone several upgrades (thanks to the continued support from a 2012 SPIE Education Outreach Grant) to better highlight these optical phenomena and make it more engaging for a wider range of audiences. This paper celebrates the continued success of the LPD and shares the knowledge gained with an overview of its design and use in STEM-based outreach events.

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Proceedings Article | 5 September 2014

Design of equiangular spiral photonic crystal fiber for supercontinuum generation at 1550 nm

T. Saini, A. Baili, V. Dahiya, A. Kumar, R. Cherif, M. Zghal, R. Sinha

Proceedings Volume 9200, 920012 (2014) https://doi.org/10.1117/12.2061806

KEYWORDS: Dispersion, Photonic crystal fibers, Glasses, Supercontinuum generation, Raman scattering, Refractive index, Fiber optic communications, Optical communications, Communication engineering, Telecommunications

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An equiangular spiral (ES) photonic crystal fiber (PCF) design in tellurite glass has been presented. The structure parameters have been tailored for zero dispersion wavelength (ZDW) at λZDW=1570 nm. The fiber structure has high nonlinearity (γ = 2000 w^-1 Km^-1) at 1550 nm wavelength with very low and flat dispersion -0.152 [ps/(nm×km)]. We have generated supercontinuum using only 2 mm length of tellurite ES PCF with low input pulse energy of 200 pJ by pumping at 1550 nm. The proposed fiber may be a suitable candidate for nonlinear applications.

Proceedings Article | 5 September 2014

2-10 µm supercontinuum broadening using a highly nonlinear chalcogenide microfiber for mid-IR applications

A. Baili, R. Cherif, T. Saini, A. Kumar, R. Sinha, M. Zghal

Proceedings Volume 9200, 92000S (2014) https://doi.org/10.1117/12.2061848

KEYWORDS: Dispersion, Mid-IR, Chalcogenides, Supercontinuum generation, Nonlinear optics, Femtosecond phenomena, Infrared spectroscopy, Waveguides, Wave propagation, Fiber lasers

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A new design of the As2Se3 microfiber has been presented. With the optimized geometric parameters: pitch Λ= 0.8 μm and five different air filling ratios varying from 0.4 to 0.95, the structure exhibits an all normal dispersion with a flat top equal to -2.3 [ps/(nm.km)], a confinement loss less than 10^-2 dB/km, and a large nonlinear coefficient equal to 7250 (w. km)^-1. Using the generalized nonlinear Schrödinger equation, we generate a very broadband supercontinuum (SC) in the mid-infrared region. By pumping the fiber at λp=5.24 μm with a femtosecond laser having 50 fs as a width with a relatively low energy of E=80 pJ, we generate a large spectrum extending from 2 μm to 10 μm in only 2 mm fiber length. The generated SC demonstrates perfect coherence property over the entire bandwidth. SC generation extended into the mid-infrared (IR) spectral region have potential usefulness in a variety of applications requiring a broad mid-IR spectrum such as fiber sensing, IR spectroscopy, fiber laser, optical tomography coherence.

Proceedings Article | 28 August 2014

Design of single-polarization single-mode photonic nanowire

A. Baili, R. Cherif, A. Ben Salem, T. S. Saini, A. Kumar, R. Sinha, M. Zghal

Proceedings Volume 9170, 917014 (2014) https://doi.org/10.1117/12.2061887

KEYWORDS: Dispersion, Cladding, Polarization, Birefringence, Fiber optic gyroscopes, Fiber optics sensors, Silica, Nanowires, Photonic nanostructures, Photon polarization

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A novel design of single polarization single mode (SPSM) photonic nanowire is proposed. Using a cladding structure with circular air holes, a new design of a photonic nanowire with ultra-wideband range of 740 nm for SPSM operation is obtained. The numerical results show that the SPSM-nanowire is low-loss within the wavelengths ranging from 1.17 μm to 1.91 μm, the confinement loss of the slow-axis mode is less than 0.15 dB/km and the fast-axis mode is unguided. This fiber has greater advantages in polarization sensitive applications, such as fiber optic gyroscopes, fiber optic current sensors, high-power fiber lasers, and coherent optical communications.

Proceedings Article | 17 July 2014

Expansion of student activities in Africa: from south to north

Rim Cherif, Amine Ben Salem, Amor Gueddana, Mourad Zghal, Darryl Naidoo, Andrew Forbes, Alexander Heidt, Erich Rohwer

Proceedings Volume 9289, 928914 (2014) https://doi.org/10.1117/12.2070775

KEYWORDS: Photonics, Communication engineering, Physics, Active optics, Roads, Ions, Optical communications, Silica, Laser marking, Electroluminescence

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Optics and photonics research in Africa has gradually grown in the past ten years with a very active optical community involved in state-of-the-art research. Despite relatively low resources, optics research in the continent is competitive with many international benchmarks and has had a significant impact within the African continent. In the past five years, a group of dynamic students have developed the student chapter network from Tunisia to South Africa. The first student chapters of the optical society of America (OSA) and the international society for optics and photonics (SPIE) were established in South Africa (in the Council for Scientific and Industrial Research (CSIR) and in the University of Stellenbosch), followed by a chapter in Tunisia (Engineering school of communications of Tunis, Sup’Com). In this paper, we will present the major activities of the student chapters of Tunisia and South Africa, and how they are promoting optics and photonics in Africa.

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Proceedings Article | 2 May 2014

New design of multicore nonlinear photonic crystal fiber for mid-IR supercontinuum generation

Amira Baili, Rim Cherif, Mourad Zghal

Proceedings Volume 9128, 91280A (2014) https://doi.org/10.1117/12.2051822

KEYWORDS: Dispersion, Supercontinuum generation, Mid-IR, Photonic crystal fibers, Chalcogenides, Nonlinear crystals, Chalcogenide glass, Optical coherence tomography, Solitons, Femtosecond phenomena

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Supercontinuum (SC) generation in six core hexagonal lattice photonic crystal fiber (PCF) made of As₂Se₃-based chalcogenide glass was numerically investigated. The fiber was excited by 50 fs input pulse with hyperbolic secant field profile with tunability range of 2.5-5.5 μm. We obtained a flat-top normal dispersion profile when choosing Λ=1 μm and d=0.9 μm. By pumping near the zero dispersion wavelength, a high coherent SC spanning over 4 μm was generated with a launched pulse energy of E= 100 pJ in only 1 cm fiber length. The generated SC is therefore ideal for applications in ultrafast science, metrology, coherent control, non-destructive testing, spectroscopy, and optical coherence tomography in the mid-infrared region.

Proceedings Article | 1 May 2014

A new design of a directional coupler for high order mode multiplexing in few mode fibers

Abderrahmen Trichili, Amine Ben Salem, Rim Cherif, Mourad Zghal, Andrew Forbes

Proceedings Volume 9131, 91310X (2014) https://doi.org/10.1117/12.2051858

KEYWORDS: Single mode fibers, Multiplexers, Multiplexing, Directional couplers, Refractive index, Telecommunications, Waveguides, Cladding, Optical communications, Wave propagation

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We propose a new and versatile design of a directional coupler able to generate and multiplex high order modes in few mode fibers. The designed device can selectively generate five high order modes and multiplex them in a few mode fiber with an overall insertion loss not exceeding 3dB at the telecommunication wavelength λ = 1550 nm. The mode dependent loss is found to be weakly dependent to the wavelength. The proposed device is very promising for high order mode multiplexing and suitable for high bit-rate optical communication systems.

Proceedings Article | 18 November 2013

Broadband coherent mid-IR supercontinuum generation using highly nonlinear tapered photonic crystal fibers

Amine Ben Salem, Rim Cherif, Mourad Zghal

Proceedings Volume 8785, 87855O (2013) https://doi.org/10.1117/12.2027491

KEYWORDS: Mid-IR, Dispersion, Solitons, Photonic crystal fibers, Supercontinuum generation, Glasses, Nonlinear crystals, Chalcogenides, Chalcogenide glass, Nonlinear optics

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We design tellurite and As₂S₃-based chalcogenide tapered photonic crystal fibers (TPCF) for broadband mid-infrared coherent supercontinuum (SC) generation in the few optical-cycle-regime. By injecting pre-chirped femtosecond pulses, the soliton self-compression is optimized and then, we show the generation of more than one octave-spanning SC spectra with low input pulse energies in both TPCF having 8 mm-length.

Proceedings Article | 28 June 2013

Characterization of Mach-Zehnder interferometer-based photonic crystal fiber sensors

Amine Ben Salem, Ahmed Dhib, Rim Cherif, Mourad Zghal

Proceedings Volume 8561, 856109 (2013) https://doi.org/10.1117/12.999507

KEYWORDS: Sensors, Photonic crystal fibers, Refractive index, Phase shifts, Waveguides, Silica, Biosensing, Mach-Zehnder interferometers, Nanowires, Photonic nanostructures

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We propose a new design of Mach-Zehnder interferometers (MZI) structure assembled with two arms composed of 400nm-diameter-hole-modified silica photonic crystal fibers (PCFs) and immersed in solvent solution. The proposed design is found to enhance considerably the sensitivity. A highly-sensitive versatile interferometry technique is used to determine the phase shift from both arms and consequently the specimen’s information can be retrieved. The proposed sensor was first tested when considering the specimen to be analyzed with different concentrations for a probing light of 325 nm. The sensitivity of detecting the benzene solutions in water reaches 9 rad/μm which is much higher compared to what was achieved in photonic nanowires. Then, the detection of corn oil into olive oil is achieved with high sensitivity of 14.7 rad/μm demonstrating that the sensor is capable of detecting a RI variation of 4×10^-7 in only 1-mm sensitive area- length. Thus, the proposed MZI-based PCF-sensor shows to be very attractive for compact, flexible and high sensitive biochemical sensing.

Proceedings Article | 8 May 2013

Ultra-broadband, mid IR and coherent supercontinuum generated in aperiodic chalcogenide photonic crystal fibers

Rim Cherif, Amira Baili, Mourad Zghal

Proceedings Volume 8772, 87720C (2013) https://doi.org/10.1117/12.2017555

KEYWORDS: Dispersion, Optical fibers, Supercontinuum generation, Mid-IR, Chalcogenides, Photonic crystal fibers, Raman spectroscopy, Nonlinear optics, Femtosecond phenomena, Chalcogenide glass

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A new design of aperiodic As2Se3-based chalcogenide photonic crystal fibers (PCF) is proposed in order to obtain broadband, mid-IR, and coherent supercontinuum (SC) sources. The proposed fibers possess an ultra-flattened dispersion curve over a wide wavelength range. The significance of this work is that it provides a new type of midinfrared SC source with flat shape, broadband and high coherence properties by femtosecond pumping the As2Se3-based PCF. The generated SC in the designed fibers cover a broadband range extending from 2 μm to more than 8 μm with a low input energy of 120 pJ and a short fiber length of 16 mm. In this context, many applications can be performed such as fiber lasers, pulse compression and multi-wavelength optical sources in the mid-infrared region.

Proceedings Article | 3 May 2013

A polarization maintaining evanescent field sensor for measuring liquid refractive index change

Rim Cherif, Amine Ben Salem, Mourad Zghal

Proceedings Volume 8775, 877505 (2013) https://doi.org/10.1117/12.2017225

KEYWORDS: Sensors, Refractive index, Silica, Waveguides, Birefringence, Polarization, Phase shifts, Finite element methods, Nanowires, Photonic nanostructures

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A modified Mach-Zehnder interferometer (MZI) design based on elliptical silica photonic nanowires is proposed and demonstrated numerically. The MZI is used as a highly sensitive evanescent field based refractive index sensor. By applying a full vectorial finite element method, single-mode operation, polarization maintaining and very high sensitivity are achieved by simply using 800 nm-elliptical silica nanowires. Using the highly-sensitive versatile interferometry technique, the phase shift from both arms is determined and consequently the specimen’s information can be retrieved. The proposed sensor is used to determine the refractive index (RI) of NaCl solutions with different concentrations. The sensor is capable of detecting a refractive index variation of the order of 10^-6 RI unit with a high sensitivity of 4.2 rad/μm.

Proceedings Article | 20 November 2012

New design of As2Se3-based chalcogenide photonic crystal fiber for ultra-broadband, coherent, mid-IR supercontinuum generation

Amira Baili, Rim Cherif, Mourad Zghal

Proceedings Volume 8564, 856409 (2012) https://doi.org/10.1117/12.1000034

KEYWORDS: Dispersion, Optical fibers, Mid-IR, Chalcogenides, Supercontinuum generation, Photonic crystal fibers, Refractive index, Fiber lasers, Solitons, Chalcogenide glass

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In this paper, we propose a new design of all-normal and ultra-flat dispersion As₂Se₃-based chalcogenide photonic crystal fibers (PCF). The generation of supercontinuum (SC) in the designed fibers is investigated, which has flat and smooth profile, covers a broad range extending from 2 to 8 μm. The significance of this work is that it provides a new type of mid-infrared SC source with flat shape, broadband and high coherence properties by pumping the As₂Se₃-based PCF. Thus many applications can be performed such as fiber lasers, pulse compression and multi-wavelength optical sources in the mid-infrared region.

SPIE Journal Paper | 3 October 2012

Highly nonlinear tapered photonic crystal fibers for broadband mid-infrared supercontinuum generation in the few-optical-cycle regime

Amine Ben Salem, Rim Cherif, Mourad Zghal

OE, Vol. 51, Issue 10, 105008, (October 2012) https://doi.org/10.1117/12.10.1117/1.OE.51.10.105008

KEYWORDS: Dispersion, Mid-IR, Solitons, Photonic crystal fibers, Nonlinear crystals, Supercontinuum generation, Chalcogenides, Picosecond phenomena, Communication engineering, Single mode fibers

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We propose a design of tellurite and As2S3-based chalcogenide tapered photonic crystal fibers (TPCF) for broadband coherent mid-infrared supercontinuum (SC) generation in the few-optical-cycle regime. We optimize the soliton self-compression by injecting pre-chirped femtosecond pulses. More than one octave-spanning SC spectra were generated in 8 mm-long in both tellurite and chalcogenide TPCF with low input pulse energies of 1 nJ and 100 pJ at pump wavelengths of 2.9 and 4.7 μm, respectively.

Proceedings Article | 16 May 2012

Sub-two-cycle soliton self-compression in a tapered tellurite photonic crystal fiber

Amine Ben Salem, Rim Cherif, Mourad Zghal

Proceedings Volume 8434, 84340B (2012) https://doi.org/10.1117/12.922273

KEYWORDS: Solitons, Dispersion, Mid-IR, Photonic crystal fibers, Glasses, Nonlinear optics, Waveguides, Optical properties, Chalcogenide glass, Nanowires

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We design tellurite tapered photonic crystal fibers (PCFs) for broadband mid-infrared supercontinuum (SC) generation in the few-optical-cycle regime. We show that we can move the zero dispersion wavelength (ZDW) beyond 2 μm toward mid-IR wavelength region by tapering tellurite PCFs. We demonstrate the generation of sub-two-cycle soliton selfcompressed pulses from 200 fs to 19.1 fs and show more than one octave-spanning coherent SC, extending from 1675 to 3950 nm, generated in 8 mm-long tapered tellurite PCF with low input pulse energy of 1 nJ at 2.9 μm.

Proceedings Article | 3 May 2012

2D real-time arithmetic operations using optical coherence properties: image processing applications

B.-E. Benkelfat, S. El Wardi, M. Zghal, A. Alfalou

Proceedings Volume 8397, 83970D (2012) https://doi.org/10.1117/12.918892

KEYWORDS: Coherence (optics), Multiplexing, Modulation, Signal processing, Interferometers, Image processing, Computer programming, Light, Electro optics, Spatial light modulators

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We report for the first time the use of the well-known coherence modulation of light in two-dimensional arithmetic operations. This method, which allows several signals to be multiplexed on a single light beam, permits parallel real-time all optical subtractions and additions. In the context of an increased need of security, a major application of our multiplexed approach could be the optical encryption of images and multi-modalities techniques in biometric domain. The single-channel optical architecture, which allows carrying out single and multiple arithmetic operations, is described and more results are presented to show the effectiveness of our technique. We have evaluated the performance of the processor in terms of noise level as a function of the continuous optical path-difference ratio.

Proceedings Article | 26 April 2012

Enhanced stimulated Brillouin scattering in tellurite microstructured fibers

Rim Cherif, Mourad Zghal, Meisong Liao, Yasutake Ohishi

Proceedings Volume 8426, 842612 (2012) https://doi.org/10.1117/12.922111

KEYWORDS: Optical fibers, Acoustics, Scattering, Finite element methods, Scanning electron microscopy, Wave propagation, Refractive index, Silica, Glasses, Electron microscopes

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We report a detailed implementation of a 2-D finite element method that is applied to calculate the stimulated Brillouin scattering (SBS) characteristics in highly nonlinear tellurite microstructured fibers. Our analysis is firstly made in four air-holes different tellurite microstructured fibers and compared to silica and chalcogenide fibers. Such fibers have drawn much interest because of their capacity of increasing the SBS gain. A Brillouin gain coefficient, gB, of 1 10^-10 m/W is found around the acoustic frequency of 8 GHz. Then, we used real scanning electron microscope images of small core highly nonlinear tellurtie fibers and compared the SBS parameters to numerical predicted results. Good agreement is found between the SBS gain coefficients and the frequency shifts.

Proceedings Article | 3 November 2011

Study of soliton self-compression in photonic nanowires

Amine Ben Salem, Rim Cherif, Mourad Zghal

Proceedings Volume 8011, 80119N (2011) https://doi.org/10.1117/12.902817

KEYWORDS: Solitons, Dispersion, Waveguides, Silica, Nonlinear optics, Ultrafast phenomena, Single mode fibers, Near infrared, Nanowires, Photonic nanostructures

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Waveguides with sub-wavelength dimensions known as photonic nanowires are among the most attractive optical structures for ultrafast nonlinear optics. They provide high nonlinearities and allow the generation of cyclical temporal compression and broadband supercontinuum in few millimeters length. In this work, we numerically investigate the soliton self-compression in photonic nanowires fabricated by tapering standard single mode fibers. We demonstrate, the generation of 1.53 fs compressed pulse (ca. 0.57 single optical cycle) from 100 fs input pulse by pumping at low input pulse energy of 2.5 nJ, a 1.15 mm-long nanowire with a diameter of 800 nm. Thus, broadband supercontinuum spanning from 260 nm to 1800 nm is generated. Air-silica nanowires present very promising coherent white-light sources and ideal waveguides for nonlinear applications such as single-cycle pulses generation and optical processing.

Proceedings Article | 22 September 2011

Multiplex coding for real-time optical image processing

S. Elwardi, B.-E. Benkelfat, M. Zghal

Proceedings Volume 8167, 81671Y (2011) https://doi.org/10.1117/12.899570

KEYWORDS: Image processing, Coherence (optics), Signal to noise ratio, Multiplexing, Modulation, Computer programming, Image quality, Signal processing, Liquid crystals, Spatial light modulators

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The latest developments in optical image processing for security, compression and cryptography require parallel real time processing and multiplexing. In this paper, we propose the application of the well-know "coherence modulation of light" technique for real-time encoding and decoding of signals which can be useful for optical image processing. This method uses the coherence properties of broadband sources for encoding signals onto light beams. One major asset of this approach, compared to other conventional optical modulation methods, is an original multiplex coding of several signals through a single light beam. We achieve simultaneous real-time all optical image processing of analog twodimensional signals and suggest a set of new criteria, based on mean square error, signal to noise ratio and peak to peak signal to noise, to improve the quality of the decoding image as function of the optical path difference and the coherence length of the source.

Proceedings Article | 26 July 2011

Generation of few optical cycles in air-silica nanowires

Amine Ben Salem, Rim Cherif, Mourad Zghal

Proceedings Volume 8001, 80011J (2011) https://doi.org/10.1117/12.892083

KEYWORDS: Solitons, Dispersion, Wave propagation, Near infrared, Ultraviolet radiation, Waveguides, Singular optics, Single mode fibers, Nonlinear optics, Nanowires

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Air-silica nanowires present suitable waveguides to enhance nonlinearities and generate cyclical temporal compression and broadband supercontinuum (SC) in only few millimeters length. We report on the generation of few optical cycles in air-silica nanowires with core diameters ranging from 400 nm to 900 nm. We show that it is possible to shift the zero dispersion wavelengths toward a wavelength of about 470 nm. We demonstrate that soliton self-compression of lowenergy 100 fs input pulse down to 1.94 fs is possible by pumping in the anomalous dispersion regime a 570 μm-long 700 nm-core diameter air-silica nanowire. We achieve a very high temporal compression ratio of 51.55 from 100 fs to less than single optical cycle. We obtain broadband supercontinuum spanning from 260 nm to 1500 nm. By adding one photon per mode noise with a random phase, a very high degree of coherence over the entire generated supercontinuum bandwidth is shown.

Proceedings Article | 11 May 2011

Full modal analysis of the stimulated Brillouin scattering in As2Se3 chalcogenide photonic crystal fiber

Rim Cherif, Amine Ben Salem, Mourad Zghal

Proceedings Volume 8073, 80732R (2011) https://doi.org/10.1117/12.886428

KEYWORDS: Acoustics, Chalcogenides, Silica, Scattering, Photonic crystal fibers, Finite element methods, Modal analysis, Glasses, Optical fibers, Chalcogenide glass

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We report a detailed implementation of a 2-D finite element method that is applied to calculate the stimulated Brillouin scattering (SBS) characteristics in As₂Se₃-based chalcogenide photonic crystal fibers (PCF). The full modal analysis of SBS is performed in both real and ideal As₂Se₃-based PCF structures taking into account the contribution of the higher order acoustic modes. Our results include the calculations of the Brillouin gain spectrum (BGS), Brillouin gain coefficient (g_B), Brillouin frequency shift (BFS), and the Brillouin threshold (P_th). The Pth in the real As₂Se₃-based chalcogenide PCF is evaluated to be around 36 mW for only 1-m length compared to hundreds of milliwatts found in the long silica PCF. We calculate, in both structures, a Brillouin gain coefficient of the fundamental acoustic mode of ~5.59 10^-9 mW^-1 at λ=1.55 μm, around the acoustic frequency of 8.08 GHz, which is more than 600 times higher than that of fused silica fiber.

SPIE Journal Paper | 1 January 2011

Low-energy single-optical-cycle soliton self-compression in air-silica nanowires

Amine Ben Salem, Rim Cherif, Mourad Zghal

JNP, Vol. 5, Issue 01, 059506, (January 2011) https://doi.org/10.1117/12.10.1117/1.3662888

KEYWORDS: Dispersion, Solitons, Nonlinear optics, Optical properties, Wave propagation, Waveguides, Communication engineering, Ultrafast phenomena, Supercontinuum generation, Nanowires

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We investigated and optimized the process of soliton self-compression in few millimeters-long air-silica nanowires. A 100 fs prechirped input pulse was compressed to a 1.4 fs pulse by pumping at very low energy of 2.5 nJ an air-silica nanowire. More than one octave spanning coherent broadband supercontinuum extending from 260 to 1800 nm was generated.

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SPIE Journal Paper | 1 September 2010

Highly nonlinear As₂Se₃-based chalcogenide photonic crystal fiber for midinfrared supercontinuum generation

Rim Cherif, Amine Ben Salem, Mourad Zghal, Pascal Besnard, Thierry Chartier, Laurent Brilland, Johann Troles

OE, Vol. 49, Issue 09, 095002, (September 2010) https://doi.org/10.1117/12.10.1117/1.3488042

KEYWORDS: Selenium, Chalcogenides, Dispersion, Supercontinuum generation, Photonic crystal fibers, Mid-IR, Nonlinear optics, Refractive index, Optical properties, Solitons

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We propose a real, highly nonlinear, As2Se3-based chalcogenide photonic crystal fiber in which a supercontinuum (SC) spanning more than 2 octaves is generated at =2.8 µm in the femtosecond regime. The designed PCF is characterized for ultrabroadband mid-infrared SC generation in only few millimetres of fiber length. A full modal analysis of the optical properties of the fiber is presented in terms of the effective area, the nonlinearity coefficient, and the chromatic dispersion. A second-order Sellmeier approximation is proposed to estimate the variation of the refractive index of the As2Se3 material as a function of wavelength. The numerical study shows that a SC spanning from 1.9 to 4 µm can be generated in the chalcogenide PCF with an air-hole diameter of 1.26 µm and a pitch of 1.77 µm. We examine the interplay of the nonlinear effects that lead to the construction of the SC as a function of the input power and the fiber length. We find that the dynamics behind the SC generation is mainly ruled by the effects of self phase modulation and stimulated Raman scattering. The intrinsic properties of the chalcogenide glasses and the microstructure provide enhanced optical properties and offer numerous applications in the infrared field.

Proceedings Article | 5 June 2009

A simple wavelength division multiplexing system for active learning teaching

Mourad Zghal, Hassen Ghalila, Zohra Ben Lakhdar

Proceedings Volume 9666, 96661R (2009) https://doi.org/10.1117/12.2208086

KEYWORDS: Wavelength division multiplexing, Physics, Photonics, Optical communications, Telecommunications, Active optics, Fiber optics, Multiplexing, Light emitting diodes, Semiconductor lasers

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The active learning project consists in a series of workshops for educators, researchers and students and promotes an innovative method of teaching physics using simple, inexpensive materials that can be fabricated locally. The objective of the project is to train trainers and inspire students to learn physics. The workshops are based on the use of laboratory work and hands-on activities in the classroom. The interpretation of these experiments is challenging for some students, and the experiments can lead to a significant amount of discussion. The workshops are organized within the framework of the project ‘‘Active Learning in Optics and Photonics” (ALOP) mainly funded by UNESCO, with the support of ICTP (Abdus Salam International Centre for Theoretical Physics) and SPIE. ALOP workshops offer high school, college or university physics teachers the opportunity to improve their conceptual understanding of optics. These workshops usually run for five days and cover several of the topics usually found in any introductory university physics program. Optics and photonics are used as subject matter because it is relevant as well as adaptable to research and educational conditions in many developing countries [1].

In this paper, we will mainly focus on a specific topic of the ALOP workshops, namely optical communications and Wavelength Division Multiplexing technology (WDM). This activity was originally developed by Mazzolini et al [2]. WDM is a technology used in fibre-optic communications for transmitting two or more separate signals over a single fibre optic cable by using a separate wavelength for each signal. Multiple signals are carried together as separate wavelengths of light in a multiplexed signal. Simple and inexpensive WDM system was implemented in our laboratory using light emitting diodes or diode lasers, plastic optical fibres, a set of optical filters and lenses, prism or grating, and photodiodes. Transmission of audio signals using home-made, simple, inexpensive electronic circuits was also demonstrated. The experimental set-up was used during national ALOP workshops. Results are presented and discussed in this paper. Current explorations to further develop these and other closely-related experiments will also be described.

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Proceedings Article | 22 April 2008

Single-sided supercontinuum generation in a photonic crystal fiber by selective excitation of the third-order mode

Rim Cherif, Mourad Zghal, Luca Tartara, Vittorio Degiorgio

Proceedings Volume 6990, 69900O (2008) https://doi.org/10.1117/12.780503

KEYWORDS: Wave propagation, Supercontinuum generation, Dispersion, Photonic crystal fibers, Solitons, Raman scattering, Numerical analysis, Femtosecond phenomena, Visible radiation, Raman spectroscopy

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We describe an experiment in which a supercontinuum spectrum is generated by exciting the third-order mode of a highly nonlinear photonic crystal fiber (PCF). Our experiment consists of launching a train of femtosecond pulses into a 45-cm-long span of a PCF by means of an offset pumping technique that can selectively excite higher-order modes. For input wavelengths below 810 nm, the fiber was found to allow for the propagation of higher-order modes. When exciting the third-order mode we were able to generate an almost purely visible supercontinuum even with pulse energies below 100 pJ. Although the spectrum broadens on the short-wavelength side down to the blue region, no components at wavelengths larger than the pump wavelength were observed. The mechanism behind the spectral broadening is mainly ruled by soliton propagation leading to the generation of a blue-shifted dispersive wave. The fact that higher-order modes have a cut-off wavelength plays a fundamental role that accounts for the observed asymmetry of spectral broadening. Our experimental results are compared with the numerical solutions of the nonlinear Schrödinger equation. Good agreement between experimental and numerical results is found.

SPIE Journal Paper | 1 December 2007

Impact of small geometrical imperfections on chromatic dispersion and birefringence in photonic crystal fibers

Mourad Zghal, Rim Cherif

OE, Vol. 46, Issue 12, 128002, (December 2007) https://doi.org/10.1117/12.10.1117/1.2821416

KEYWORDS: Dispersion, Birefringence, Optical fibers, Photonic crystal fibers, Finite element methods, Optical engineering, Polarization, Telecommunications, Silica, Scanning electron microscopy

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Slight geometrical imperfections that can occur during the fabrication process, in the lattice of index-guiding photonic crystal fibers (PCF), are evaluated to determine the sensitivity of the chromatic dispersion and the birefringence to these defects. Furthermore, the impact of fluctuations in the lattice profile of a real photonic crystal fiber on its propagation characteristics is pointed out. Numerical and experimental analyses show that chromatic dispersion of a large core PCF is more robust to the geometrical imperfections, while its birefringence reveals more sensitivity to these defects. This analysis is performed using the finite element method, which assures high solution accuracy.

Proceedings Article | 30 October 2007

Compensation of optical pulse broadening in photonic crystal fibers using Kerr effect

Rim Cherif, Mourad Zghal, Habib Hamam

Proceedings Volume 6796, 679637 (2007) https://doi.org/10.1117/12.779225

KEYWORDS: Dispersion, Wave propagation, Solitons, Kerr effect, Scanning probe microscopy, Photonic crystal fibers, Phase modulation, Fourier transforms, Ultrafast phenomena, Silica

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We investigated the dispersion compensation by means of self phase modulation induced by the nonlinear Kerr effect in photonic crystal fibers (PCF). Accurate calculations of both chromatic dispersion and nonlinear coefficient in small core PCF were performed using a vector finite element method. Besides, ultrashort pulse propagation in PCF was simulated using the generalized nonlinear Schrodinger equation. Conditions necessary for the formation of soliton during propagation of a femtosecond pulse were investigated. To compensate the broadening caused by dispersion, we thoroughly examined the pulse propagation in the anomalous dispersion regime at the wavelength λ=810nm. The study showed that by carefully selecting laser and PCF parameters, the pulse broadening and frequency chirping, due to group velocity dispersion of the PCF, can be compensated by using the Kerr nonlinearity of the medium.

Proceedings Article | 26 October 2007

All-optical variable delay for re-circulating buffers based on fiber Bragg grating

Mohamed Amine Jebali, Mourad Zghal, NourEddine Boudriga, Habib Hamam

Proceedings Volume 6796, 679634 (2007) https://doi.org/10.1117/12.779116

KEYWORDS: Fiber Bragg gratings, Polarization, Polarizers, Modulation, Computer architecture, Liquid crystals, All optical signal processing, Control systems, Optical components, Optical fibers

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Optical buffers are central elements in all-optical switched networks to avoid packet contention and loss. With actual traveling buffers, the delay time is discrete and predetermined by the length of the optical fiber delay line (FDL). Traveling buffers are bulky, since a large number of delay lines are required to handle multiple traffics. In this paper, we designed a variable optical delay line based on a re-circulating loop that is controlled by all-optical signal processing technology. We showed that a FDL based on fiber Bragg gratings (FBG) in combination with a single optical wavelength converter can realize variable delays. A simulator was developed to evaluate the performance and limitations of the proposed architecture.

SPIE Journal Paper | 1 September 2007

Improving triangular-lattice photonic-crystal-fiber couplers by introducing geometric nonuniformities

Mourad Zghal, Rim Cherif, Faouzi Bahloul

OE, Vol. 46, Issue 09, 095004, (September 2007) https://doi.org/10.1117/12.10.1117/1.2783388

KEYWORDS: Polarization, Wave propagation, Optical engineering, Beam propagation method, Directional couplers, Radio propagation, Refractive index, Waveguides, Birefringence, Wavelength division multiplexing

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The coupling characteristics of newly proposed photonic-crystal-fiber couplers are rigorously analyzed using a 3-D finite-difference vector beam propagation method. The coupling length and efficiency of the couplers are investigated as a function of their geometrical parameters at different wavelengths. Size variability of the central hole is considered as a means of improving the coupling between the two cores. A determination of the guiding properties of the couplers, such as the propagation constants and the effective indices, is performed using a mode solver based on the plane-wave method. We show that it is possible to design very short photonic-crystal-fiber couplers with submillimeter coupling lengths. Nonuniformities are deliberately introduced in the coupler pattern to decrease the coupling length in comparison with the ideal structures. This study confirms that the designed coupler can act as an efficient ultrasmall-wavelength splitter or polarization-preserving directional coupler for wavelength division multiplexing systems.

Proceedings Article | 3 June 2007

The first steps for learning optics: Ibn Sahl's, Al-Haytham's and Young's works on refraction as typical examples

Mourad Zghal, Hamid-Eddine Bouali, Zohra Ben Lakhdar, Habib Hamam

Proceedings Volume 9665, 966509 (2007) https://doi.org/10.1117/12.2207465

KEYWORDS: Refraction, Cameras, Geometrical optics, Eye, Visualization, Sun, Optical properties, Mirrors, Visual optics, Spherical lenses

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Optics scholars did not only discover optical phenomena and laws governing them. Some of them also invented impressive optical systems and instruments or offered us techniques to juggle with optical signals and rays. One typical example of the impressive optical systems is the camera obscura invented by Ibn Al-Haytham. For techniques enabling us to easily handle optical rays, one can mention Young’s method to handle rays put into play by refraction. Nine centuries before him, Ibn Sahl proposed an elegant method to manipulate refraction related rays. These three examples will be handled in this paper, together with a historical overview inviting the reader to be in the context of this fascinating works.

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Proceedings Article | 18 April 2006

Full vector beam propagation method modelling of dual core photonic crystal fiber couplers

Rim Cherif, Mourad Zghal, Rihab Chatta, Chedlia Ben Neila

Proceedings Volume 6182, 61822K (2006) https://doi.org/10.1117/12.662477

KEYWORDS: Polarization, Photonic crystal fibers, Beam propagation method, Wave propagation, Directional couplers, Modeling, Radio propagation, Waveguides, Optical fibers, Refractive index

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We analyse the coupling characteristics of dual-core photonic crystal fibre couplers by a 3D finite difference vector beam propagation method. Beam propagation analysis of photonic crystal fibre couplers is performed in terms of coupling length and coupling efficiency. The determination of the guiding properties such as the propagation constants is evaluated using a mode solver based on plane wave method. We study the influence of the photonic crystal fibre coupler geometrical parameters on the coupling length at different wavelengths. Variable size of the central hole is considered to improve the coupling between the two cores. It is shown that it is possible to design shorter photonic crystal fibre couplers with coupling lengths of hundred micrometers compared to conventional optical fibre couplers. We demonstrate that the designed coupler can operate as a polarization preserving directional coupler. This study confirms that this device can act as an efficient ultra small wavelength selective coupler.

Proceedings Article | 24 October 2005

Popularisation of optical phenomena: establishing the first Ibn Al-Haytham workshop on photography

Hamid-Eddine Bouali, Mourad Zghal, Zohra Ben Lakhdar

Proceedings Volume 9664, 966422 (2005) https://doi.org/10.1117/12.2207764

KEYWORDS: Cameras, Photography, Optical properties, Sun, Earth's atmosphere, Photonics, Image quality, Digital photography, Physics, Psychology

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Within the framework of its scientific activities, the Optical Society of Tunisia organized the first photographic workshop called Ibn Al-Haytham session. This activity enabled, through conferences, the evocation of the research done by one of the most distinguished and prolific mathematicians in the medieval tradition of Arabic Islamic science. The camera obscura that he thoroughly studied was the theme of a training where more than twenty participants build and used this basic camera. The adopted training approach based on active teaching and learning made possible the achievements of interesting results in spite of the heterogeneity of the group of trainees.

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Proceedings Article | 22 April 2005

Misalignment loss at hybrid standard-single-mode-fibre/microstructured-optical-fibre connections

Faouzi Bahloul, Mourad Zghal, Rihab Chatta, Rabah Attia, Dominique Pagnoux, Philippe Roy

Proceedings Volume 5830, (2005) https://doi.org/10.1117/12.618767

KEYWORDS: Micro optical fluidics, Single mode fibers, Structured optical fibers, Optical fibers, Fiber optic communications, Optical communications, Connectors, Fusion splicing, Optical alignment, Chlorine

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We present experimental results on Microstructured Optical Fibre (MOF) coupling with standard Single Mode Fibre (SMF) using a simple and reliable set-up. An electric-arc splicing system is used to demonstrate its effectiveness in splicing SMF with MOFs. The measurements of the additional loss induced by transverse and longitudinal offsets at connections between SMF and MOF are reported and discussed. The influence of mode size mismatch is emphasized.

Proceedings Article | 22 October 2004

Full vector modal analysis of microstructured optical fiber propagation characteristics

Mourad Zghal, Faouzi Bahloul, Rihab Chatta, Rabah Attia, Dominique Pagnoux, Philippe Roy, Gilles Melin, Laurent Gasca

Proceedings Volume 5524, (2004) https://doi.org/10.1117/12.558999

KEYWORDS: Micro optical fluidics, Finite element methods, Structured optical fibers, Radio propagation, Dispersion, Silica, Electromagnetism, Refractive index, Cladding, Optical fibers

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Microstructured optical fibers (MOFs) are optical fibers having a periodic air-silica cross-section. The air holes extend along the axis of the fiber for its entire length. The core of the fiber is formed by a missing hole in the periodic structure. Remarkable properties of MOFs have recently been reported. This paper presents new work in the modeling of the propagation characteristics of MOFs using the Finite Element Method (FEM) and the Galerkin Method (GM). This efficient electromagnetic simulation package provides a vectorial description of the electromagnetic fields and of the associated effective index. This information includes accurate determination of the spectral extent of the modes, cutoff properties and mode-field distributions. We show that FEM is well adapted for describing the fields at abrupt transitions of the refractive index while GM has the advantage to accurately analyze MOFs of significant complexity using only modest computational resources. This presentation will focus on the specific techniques required to determine single mode operation, dispersion properties and effective area through careful choice of the geometrical parameters of the fibers. We demonstrate that with suitable geometrical parameters, the zero dispersion wavelength can be shifted. This tool can also provide design criteria for fabricating MOFs and a corresponding map of effective area. This approach is validated by comparison with experimental results and measurements on actual MOFs fabricated at IRCOM and at Alcatel Research and Innovation Center.

Proceedings Article | 4 September 2002

Numerical solution to modal field equation with a finite difference beam propagation method: application to Bragg fiber

Rihab Chatta, Mehdi Ammar, Mourad Zghal, Rabah Attia

Proceedings Volume 4769, (2002) https://doi.org/10.1117/12.481183

KEYWORDS: Beam propagation method, Atmospheric propagation, Numerical analysis, Wave propagation, Optical fibers, Structured optical fibers, Optical simulations, Refractive index, Diffraction, Charge-coupled devices

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The Beam Propagation Method (BPM) is the most widely used tool for the investigation of complex photonic structures. Since the original BPM was introduced, many improvements and extensions have been proposed. We have developed a computer program based on the Finite Difference BPM for modeling propagation in optical waveguides. This method has been successfully applied for several 3D problems such as propagation on Bragg Fiber. The main drawback of this method is its complexity and long computation time using a personal computer. In this paper, a simple efficient numerical solution method, we called double 2D-BPM, is proposed. This technique is based on the decomposition of the 3D field propagation equation onto two 2D equations related to transverse plans. Propagation along the x and y axes is computed separately in two steps. Using a similar technique, a finite difference approximation for each propagation step involves the solution of two equations and the complete problem splits into two independent 2D problems. We performed propagation tests in elementary 3D problems but also on Bragg fiber. The numerical results of 3D-BPM and double 2D-BPM have been compared. The propagation step along the propagation axis has been experimentally determined. Parameters that affect the accuracy and the stability of this method were discussed. Losses induced by propagation on Bragg fiber were also considered. We have established that the global effect of the double 2D-BPM is equivalent to 3D-BPM technique. Comparison with exact results obtained from analytical expressions also shows excellent agreement.

Proceedings Article | 29 June 2001

v3 band of methane molecule with tunable diode laser absorption spectroscopy

Mourad Zghal, Mokhtar Saidi, Zohra Ben Lakhdar, Ammar Bouallegue

Proceedings Volume 4430, (2001) https://doi.org/10.1117/12.432901

KEYWORDS: Absorption, Methane, Semiconductor lasers, Fabry–Perot interferometers, Tunable diode lasers, Molecular lasers, Absorption spectroscopy, Atmospheric monitoring, Diodes, Molecules

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Tunable diode laser spectrometers are extensively used for the monitoring of trace gases in the atmosphere. We present the results of experimental researches on atmospheric methane concentration, responsible for industrial pollution in Tunisia. Pulsed and tunable, 3.31 micrometers lead salt, single mode, cryogenically cooled diode laser was employed. Evolution of the laser signal corresponding to methane absorption was observed. The gas to be sampled flows through an optical cell or in open-atmosphere-path. Detection was carried out by observing infrared absorption lines. An acquisition system was developed and data were stored and treated online. Traces of methane at the level of 100 ppb could be detected. This gives access to information involving methane concentration in local atmosphere.

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