Academic literature on the topic 'Guided slow-modes'
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Journal articles on the topic "Guided slow-modes"
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JIANG, YONG-YUAN, and ZONG-JING SHEN. "GUIDING CHARACTERISTICS OF AN AIR WAVEGUIDE WITH LEFT-HANDED METAMATERIALS CLADDING." Journal of Nonlinear Optical Physics & Materials 17, no. 04 (2008): 465–71. http://dx.doi.org/10.1142/s021886350800441x.
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The characteristics of guided modes of a planar waveguide in which an air core is sandwiched by two left-handed metamaterials are studied. The dispersion relation of the guided modes in this air waveguide is derived where the left-handed metamaterials claddings can be either isotropic or uniaxially anisotropic. We analyze the fast and slow wave characteristics of the guided modes. The problem of whether the dispersion relation of slow wave modes has a solution is explored. The relation between the electromagnetic parameters of the waveguide and the solution of the dispersion relation of the slow wave modes is discussed in detail.
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KURT, H. "ALL-DIELECTRIC PERIODIC MEDIA ENGINEERED FOR SLOW LIGHT STUDIES." International Journal of Modern Physics B 27, no. 27 (2013): 1330020. http://dx.doi.org/10.1142/s021797921330020x.
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The paper presents various novel approaches to implementing slow light media by manipulating the group velocity via dispersion engineering of guided modes. Light is confined and then linked with a low group velocity inside a photonic crystal waveguide (PCW) and at the PC-air interface. We discuss both basic and engineered slow light waveguide structures. The structural changes in PCs greatly modify the spectral characteristics of the dispersion curves. The search for flat bands gives rise to various strategies for slowing the optical pulses. An appropriate and commonly adopted figure of merit (FOM) is accepted to quantify and characterize the performance of the designed slow light devices. The trade-off relationship between the group index and the bandwidth is highlighted. Efficient excitation of slow modes demands the design of additional interfaces as couplers between the input waveguide and slow mode guide structure. Other challenges of slow light studies, such as various loss sources, are mentioned. Finally, the potential applications of slow light are outlined, and remarks on future directions are presented.
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Liu, Qi, and Qi Chao Liu. "Slow Light Properties of 2D Photonic Crystal Waveguide for Optical Storage in Optical Computers." Advanced Materials Research 452-453 (January 2012): 1210–14. http://dx.doi.org/10.4028/www.scientific.net/amr.452-453.1210.
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Slow light properties of the photonic crystal line-defect waveguide are researched with the plane wave expansion method. The structure of the waveguide is adjusted with several methods mentioned above at the same time and the slow light properties get better. For the structure of dielectric rods, central frequency and the group velocity of the guided modes decrease with the increase of the radii of the defected rods as well as the dielectric constant. Effects on the slow light from the change of the defected rods’ position are also studied, through moving the rods up and down; we get the almost linear guide mode which has flat slow light curve and smaller group velocity. In a word, group velocity of the slow light is mainly affected by the radii and dielectric constant of the defected rods, and group velocity dispersion is decided by the change of the defected rods’ location.
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Amorntep, W., and P. Wanchai. "Guided Modes of Slow Photon in Silicon Photonic Crystal Waveguide with Honeycomb Lattice." Advanced Science Letters 19, no. 3 (2013): 893–97. http://dx.doi.org/10.1166/asl.2013.4829.
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Li, Guofeng, Junbo Yang, Zhaojian Zhang, et al. "Double Electromagnetically Induced Transparency and Its Slow Light Application Based on a Guided-Mode Resonance Grating Cascade Structure." Materials 13, no. 17 (2020): 3710. http://dx.doi.org/10.3390/ma13173710.
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In recent years, the achievement of the electromagnetically induced transparency (EIT) effect based on the guided-mode resonance (GMR) effect has attracted extensive attention. However, few works have achieved a double EIT-like effect using this method. In this paper, we numerically achieve a double EIT-like effect in a GMR system with a three-layer silicon nitride waveguide grating structure (WGS), using the multi-level atomic system model for theoretical explanation. In terms of slow light performance, the corresponding two delay times reach 22.59 ps and 8.43 ps, respectively. We also investigate the influence of wavelength detuning of different GMR modes on the transparent window and slow light performance. Furthermore, a wide-band flat-top transparent window was also achieved by appropriately adjusting the wavelength detuning between GMR modes. These results indicate that the EIT-like effect in the WGS has potential application prospects in low-loss slow optical devices, optical sensing, and optical communications.
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Djuve, Vilde Lunnan, Carl Henrik Knutsen, and Tore Wig. "Patterns of Regime Breakdown Since the French Revolution." Comparative Political Studies 53, no. 6 (2019): 923–58. http://dx.doi.org/10.1177/0010414019879953.
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We present a temporally fine-grained data set on regimes, defined as the formal and informal rules essential for selecting leaders. The data set comprises more than 2,000 regimes from 197 polities, 1789 to 2016. We highlight how the frequency of breakdowns and particular modes of breakdown have followed cyclical rather than monotonic patterns across modern history. The most common breakdown modes, overall, are coups and incumbent-guided regime transformations. Furthermore, we report robust evidence that low income, slow or negative growth, and intermediate levels of democracy predict a higher likelihood of regime breakdown. Yet, by running change-point analysis we establish that breakdown risk has cycled substantively across periods of modern history, and the aforementioned explanatory factors are more clearly related to breakdown during certain periods. When disaggregating different breakdown modes, low income is related to, for example, breakdown due to popular uprisings, whereas intermediate democracy levels clearly predict coup-induced breakdowns and incumbent-guided transitions.
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Kumari, Sheelu, Vibha Rani Gupta, and Shweta Srivastava. "Analysis of Narrow Slot Loading on a Half Guided Wavelength Folded Substrate Integrated Waveguide." ECTI Transactions on Electrical Engineering, Electronics, and Communications 19, no. 2 (2021): 174–81. http://dx.doi.org/10.37936/ecti-eec.2021192.241655.
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In this paper, effects due to variation in positioning, width and length of a narrow slot loaded on central metal septum of a half guided wavelength Folded Substrate Integrated Waveguide (FSIW) segment is presented. The study shows that the most significant effect is due to variation in slot length. It was observed that the slot loading can be used both for slow wave structure and filter depending on the length of the slot. The smaller lengths of the slot provide the slow wave effect, whereas the longer lengths result in filtering effect. Both the phenomena are explained with the help of field diagrams for different propagating modes and extracted equivalent circuit for the Slot Loaded Folded Substrate Integrated Waveguide (SFSIW) segment. This study will help in deciding the dimensions of the slot as per application. The measured scattering parameters of the fabricated structure are compared with the simulated results obtained from the HFSS and the circuit simulator in ADS and are in good agreement.
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Fayard, Nikos, Adrien Bouscal, Jeremy Berroir, et al. "The comb waveguide: a new tool for strong interaction between atoms and light." EPJ Web of Conferences 266 (2022): 08002. http://dx.doi.org/10.1051/epjconf/202226608002.
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Coupling quantum emitters and nanostructures, in particular cold atoms and waveguides, has recently raised a large interest due to unprecedented possibilities of engineering light-matter interactions. However, the implementation of these promising concepts has been hampered by various theoretical and experimental issues. In this work, we propose a new type of periodic dielectric waveguide that provides strong interactions between atoms and guided photons with an unusual dispersion. We design an asymmetric comb waveguide that supports a slow mode with a quartic (instead of quadratic) dispersion and an electric field that extends far into the air cladding for an optimal interaction with atoms. We compute the optical trapping potential formed with two guided modes at frequencies detuned from the atomic transition. We show that cold Rubidium atoms can be trapped as close as 100 nm from the structure in a 1.3-mK-deep potential well. For atoms trapped at this position, the emission into guided photons is largely favored, with a beta factor as high as 0.88 and a radiative decay rate into the slow mode 10 times larger than the free-space decay rate.
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Claes, N., and R. Keppens. "Thermal stability of magnetohydrodynamic modes in homogeneous plasmas." Astronomy & Astrophysics 624 (April 2019): A96. http://dx.doi.org/10.1051/0004-6361/201834699.
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Context. Thermal instabilities give rise to condensations in the solar corona, and are the most probable scenario for coronal rain and prominence formation. We revisit the original theoretical treatment done by Field (1965, ApJ, 142, 531) in a homogeneous plasma with heat-loss effects and combine this with state-of-the-art numerical simulations to verify growth-rate predictions and address the long-term non-linear regime. We especially investigate interaction between multiple magnetohydrodynamic (MHD) wave modes and how they in turn trigger thermal mode development. Aims. We assess how well the numerical MHD simulations retrieve the analytically predicted growth rates. We complete the original theory with quantifications of the eigenfunctions, calculated to consistently excite each wave mode. Thermal growth rates are fitted also in the non-linear regime of multiple wave–wave interaction setups, at the onset of thermal instability formation. Methods. We performed 2D numerical MHD simulations, including an additional (radiative) heat-loss term and a constant heating term to the energy equation. We mainly focus on the thermal (i.e. entropy) and slow MHD wave modes and use the wave amplitude as a function of time to make a comparison to predicted growth rates. Results. It is shown that the numerical MHD simulations retrieve analytically predicted growth rates for all modes, of thermal and slow or fast MHD type. In typical coronal conditions, the latter are damped due to radiative losses, but their interaction can cause slowly changing equilibrium conditions which ultimately trigger thermal mode development. Even in these non-linear wave-wave interaction setups, the growth rate of the thermal instability agrees with the exponential profile predicted by linear theory. The non-linear evolutions show systematic field-guided motions of condensations with fairly complex morphologies, resulting from thermal modes excited through damped slow MHD waves. These results are of direct interest to the study of solar coronal rain and prominence fine structure. Our wave–wave interaction setups are relevant for coronal loop sections which are known to host slow wave modes, and hence provide a new route to explain the sudden onset of coronal condensation.
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Yu, Pengchao, Volodymyr I. Fesenko, and Vladimir R. Tuz. "Dispersion features of complex waves in a graphene-coated semiconductor nanowire." Nanophotonics 7, no. 5 (2018): 925–34. http://dx.doi.org/10.1515/nanoph-2018-0026.
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AbstractThe dispersion features of a graphene-coated semiconductor nanowire operating in the terahertz frequency band are consistently studied in the framework of a special theory of complex waves. Detailed classification of the waveguide modes was carried out based on the analysis of characteristics of the phase and attenuation constants obtained from the complex roots of characteristic equation. With such a treatment, the waves are attributed to the group of either “proper” or “improper” waves, wherein their type is determined as the trapped surface waves, fast and slow leaky waves, and surface plasmons. The dispersion curves of axially symmetric TM0n and TE0n modes, as well as nonsymmetric hybrid EH1n and HE1n modes, were plotted and analyzed in detail, and both radiative regime of leaky waves and guided regime of trapped surface waves are identified. The peculiarities of propagation of the TM modes of surface plasmons were revealed. Two subregions of existence of surface plasmons were found out where they appear as propagating and reactive waves. The cutoff conditions for higher-order TM modes of surface plasmons were correctly determined.
Dissertations / Theses on the topic "Guided slow-modes"
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Mahapatra, Sukanya. "Developing slow-mode nanophotonic platform for strong interaction between cold Rb atoms and guided photons." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP022.
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Cette thèse présente les résultats de recherche obtenues au course de ma thèse portant sur la conception, la fabrication et les premières caractérisations optiques de guides d’ondes à cristal photonique à mode lent à base de GaInP, destinés à la forte interaction des photons guidés avec la transition D₂ (780 nm) des atomes de ⁸⁷Rb. L’approche choisie implique le couplage des atomes au mode optique guidé, un concept appelé électrodynamique quantique en guide d’ondes (QED en guide d’ondes). Les guides d’ondes à cristal photonique ont été conçus avec une ingénierie de dispersion pour atteindre un mode lent ayant des indices de groupe élevés (∼ 30 - 50) autour de 780 nm. La conception, la tolérance de fabrication a été prise en compte pour garantie un mode lent sur une bande d’environ 10 nm. Le guide d’ondes est destiné à être suspendu, permettant ainsi un espace libre autour de lui pour faciliter le transport des atomes à proximité et le couplage de la lumière depuis une source laser externe. Les détails sur le processus de nanofabrication optimisé et reproductible sont donnés dans cette thèse. Les défis rencontrés lors de la fabrication et les solutions apportées ont été abordés, suivis d’une analyse des résultats de la fabrication des nanostructures. Une caractérisation optique préliminaire des guides d’ondes a été réalisée, au cours de laquelle les spectres de transmission de différentes nanostructures ont été mesurés<br>This thesis presents the results of my PhD research on the design, fabrication, and first optical characterisation of GaInP-based slow-mode nanophotonic waveguides intended for the strong interaction of guided photons with the D₂ transition (780 nm) of ⁸⁷Rb atoms. The approach involves coupling atoms to the guided mode of a waveguide, a concept referred to as Waveguide Quantum Electrodynamics (Waveguide QED). The photonic crystal waveguides were designed with dispersion engineering to achieve slow mode with high group indices (∼30 - 50) around 780 nm. In the design, fabrication tolerance has been addressed by ensuring guided mode over a bandwidth of ∼10 nm. The waveguide is intended to be suspended, allowing free space around its vicinity to facilitate the convenient transport of atoms to its proximity and easy coupling of light from an external laser source. Details on an optimized and reproducible nanofabrication process have been reported. The encountered fabrication challenges and the corresponding solutions have been addressed, followed by an analysis of the fabrication results. A preliminary optical characterisation of the waveguides was conducted, in which the transmission spectra featuring the guided mode around 780nm were observed
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Zang, Xiaorun. "Lumière lente dans les guides à cristaux photoniques pour l'interaction renforcée avec la matière." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0172/document.
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Dans cette thèse, nous avons étudié l'impact considérable de désordre aléatoire sur le transport de la lumière lente dans les guides à cristaux photoniques 1D, c'est-à-dire la localisation de la lumière. Les mesures en champ proche, les simulations statistiques et le modèle théorique révèlent l'existence d'une limite inférieure de l’extension spatiale des modes localisés. Nous avons également présenté que le niveau de désordre et l’extension spatiale de mode localisé individuelle sont liés par la masse effective de photons plutôt que la vitesse de groupe considérant en général.Deuxièmement, les systèmes hybrides d'atomes froids et des guides à cristaux photoniques ont été reconnus comme un approche prometteuse pour l'ingénierie grande interaction lumière-matière au niveau des atomes et des photons individuels. Dans cette thèse, nous avons étudié la physique, à savoir le transport de la lumière dans des guides de nanophotonique périodiques couplées à des atomes à deux niveaux. Notre expression semi-analytique développée est générale et peut rapidement caractériser le couplage entre les atomes froids et les photons guidées. Pour surmonter les difficultés techniques considérables existent dans les systèmes hybrides atomique et photonique, nous avons conçu un guide nanophotonique qui supporte un mode de Bloch lente guidée avec grande queue évanescente dans l'espace libre pour les atomes froids de piégeage. Pour adapter précisément la région de fréquence de la lumière lente du mode guidé à la ligne de transition atomique, nous avons conçu la bande photonique et de la courbe de dispersion du mode guidé afin que la force de l'interaction est robuste contre imprévisible fabrication imperfection<br>In this thesis, we firstly investigated the striking influence of random disorder on light transport near band edges in one dimensional photonic crystal wave guides, i.e. light localization. Near-field measurements, statistical simulations and theoretical model revealed the existence of a lower bound for the spatial extent of localized modes. We also showed that the disorder level and the spatial extent of individual localized mode is linked by the photon effective mass rather than the generally considered group velocity. Secondly, hybrid cold atoms and photonic crystal wave guides system have been recognized as a promising paradigm for engineering large light-matter interaction at single atoms and photons level. In this thesis, we studied the basic physics, i.e. light transport in periodic nanophotonic wave guides coupled to two-level atoms. Our developed general semi-analytical expression can quickly characterize the coupling between cold atoms and guided photons. Aim to overcome the significant technical challenges existed for developing hybrid atom-photonic systems, we designed a nanophotonic waveguide, which supports a slow guided Bloch mode with large evanescent tail in free space for cold atoms trapping (release the limitation imposed by Casmir Polder force and technical challenge of nanoscale manipulation of cold atoms). To match precisely the slow light region of the guided mode to the atomic transition line, we carefully engineered the photonic band and the dispersion curve (i.e.flatness) of the guided mode so that the interaction strength is robust against unpredictable fabrication imperfection
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Faggiani, Rémi. "Resonant nanophotonics : structural slow light and slow plasmons." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0396/document.
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L'augmentation de l'interaction lumière-matière aux échelles micro et nanométriques est un des fers de lance de la nanophotonique. En effet, le contrôle de la répartition spatiale de la lumière grâce à l'interaction résonante entre nanostructures et ondes électromagnétiques a conduit aux développements de nombreuses applications dans des domaines variés tels que les télécommunications,la spectroscopie et la détection d'objets. Le ralentissement de la lumière, sujet de la thèse, obtenue grâces à l'interférence d'ondes contre-propageantes dans des milieux périodiques ou le confinement sub-longueur d'onde dans des guides d'ondes plasmoniques, est associé à une compression des pulses lumineux et une forte augmentation du champ électrique, deux phénomènes clés pour la miniaturisation de composées optiques et l'augmentation de l'interaction lumière matière<br>Enhancing light-matter interactions at micro and nanoscales is one of the spearheads of nanophotonics. Indeed, the control of the field distribution due to the resonant interaction of nanostructures with electromagnetic waves has prompted the development of numerous optical components for many applications in telecommunication, spectroscopy or sensing. A promising approach lies in the control of light speed in nanostructures. Light slowdown, obtained by wave interferences in periodic structures or subwavelength confinement in plasmonic waveguides, is associated to pulse compressions and large field enhancements,which are envisioned as key processes for the miniaturization of optical devices and the enhancement of light-matter interactions.The thesis studies both fundamental aspects and possible applications related to slow light in photonic and plasmonic nanostructures. In particular, we study the impact of periodic system sizes on the group velocity reduction and propose a novelfamily of resonators that implement slow light on very small spatial scales. We then investigate the role of fabrication disorder in slow periodic waveguides on light localization and demonstrate how modal properties influence the confinement of localized modes. Also we propose a new hollow-core photonic crystal waveguide that provides efficient and remote couplings between the waveguide and atoms thatare trapped away from it. Finally we demonstrate the important role played by slow plasmons on the emission of quantum emitters placed in nanogap plasmonic antennas and explain how large radiation efficiency can be achieved by overcoming quenching in the metal. Additionally, one part of the thesis is devoted to thederivation of a novel modal method to accurately describe the dynamics of plasmonic resonators under short pulse illumination
Conference papers on the topic "Guided slow-modes"
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Rosiek, Christian Anker, Guillermo Arregui, Anastasiia Vladimirova, et al. "Measuring Propagation Loss in Slow-light Valley-Hall Photonic Topological Waveguides." In CLEO: Applications and Technology. Optica Publishing Group, 2023. http://dx.doi.org/10.1364/cleo_at.2023.jtu2a.146.
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We measure the propagation loss in trivial and topological slow-light guided interface modes of a valley-Hall photonic topological insulator indicating that there is no topological protection from fabrication-induced disorder.
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Murdoch, S. G., R. Leonhardt, and J. D. Harvey. "Polarisation Modulation Instability in Weakly Birefringent Fibres." In Nonlinear Guided Waves and Their Applications. Optica Publishing Group, 1995. http://dx.doi.org/10.1364/nlgw.1995.nsab2.
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Modulation instability (MI) is a phenomenon exhibited by waves propagating in nonlinear dispersive media, in which weak amplitude perturbations at different frequencies are subject to gain. In the scalar description of wave propagation in optical fibres governed by the nonlinear Schrödinger equation (NLSE), MI can occur only in the anomalous dispersion regime, and this was the first form of MI to be observed [1]. Soon after this observation, however, it was predicted that the coherent interaction of two different circularly polarised waves of the same frequency propagating in a birefringent fibre would give rise to modulation instability in both the normal and the anomalous dispersion regimes [2,3]. To our knowledge this prediction has not been experimentally verified. Modulation instability has however, been observed in the normal dispersion regime by pumping highly birefringent fibres with intense red or green pulses [4,5]. This form of MI arises from the incoherent interaction of two linearly polarised pulses propagating down the fast and slow axes of the fibre simultaneously. In these highly birefringent fibres, the terms which give rise to the coherent MI can be neglected in view of the large wavevector mismatch between the orthogonal modes. We report here the first observation of "polarisation modulation instability" (PMI). This instability possesses different characteristics depending on whether the pump is on the fast or slow axis.
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Teixeiro, M. Quiroga, D. Anderson, P. Andrekson, A. Berntson, and M. Lisak. "Efficient soliton compression by rapidly increasing amplification." In Nonlinear Guided Waves and Their Applications. Optica Publishing Group, 1996. http://dx.doi.org/10.1364/nlgw.1996.sad.12.
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Access to soliton pulses of short pulse duration is an important prerequisite in many applications of solitons for optical fibre communication purposes. A number of methods for compressing solitons in optical fibers without generating nonsolitonic radiation modes has been suggested, e.g. adiabatic soliton compression by slow amplification [1] or by slowly decreasing dispersion [2]. In the present work we show that a properly tailored and rapidly increasing gain in an optical fiber can provide a fast, but still adiabatic, soliton amplification and concomitant efficient soliton compression for fiber lengths even shorter than the characteristic dispersion length. Using the variational approach, [3], explicit expressions are given for the required variation of the inhomogeneous gain and the resulting pulse compression. The validity of the analytical predictions are verified by comparison with numerical simulations of the pulse dynamics.
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Chee, J. K., and J. M. Liu. "Parametric Frequency Conversion in a Highly Birefringent Fiber." In Nonlinear Guided-Wave Phenomena. Optica Publishing Group, 1989. http://dx.doi.org/10.1364/nlgwp.1989.thb12.
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A wide variety of nonlinear optical phenomena, such as stimulated Raman scattering[1], stimulated four-photon mixing[2], and sum-frequency generation[3], have been observed in optical fibers. For four-photon mixing in a fiber, phase matching condition has to be satisfied as well as conservation of energy. This has been successfully demonstrated both in multimode and single-mode fibers[4,5]. In a single-mode birefringent fiber, the birefringence in the fiber can compensate for the material dispersion[6,7]. Four-photon parametric process in single-mode birefringent fibers has been observed by Stolen et al. [6] when the pump polarization was along the slow axis and the Stokes and anti-Stokes pair were generated with a polarization along the fast axis with a large frequency shift. Later, Stenersen et al. [7] reported four-photon mixing with a relatively small frequency shift in highly birefringent single-mode fibers by divided pump between different polarization modes and phase-matched totally non-degenerate four-photon mixing by the pump, Stokes, and stimulated Raman Stokes to generate a new frequency. In this paper, we report the observation of various third-order nonlinear optical processes following parametric four-photon mixing in a highly birefringent fiber.
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Ge, Chang, and Fumio Koyama. "Modeling of Surface Grating-loaded VCSEL with Slowing Light." In JSAP-OSA Joint Symposia. Optica Publishing Group, 2021. http://dx.doi.org/10.1364/jsap.2021.10a_n405_5.
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In contrast to DFB lasers and DBR lasers [1, 2] with guided modes, we proposed and demonstrated surface grating VCSEL [3] where light travels as ‘Zigzag’ format in lateral direction, leading to slow-wave.
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Zheng, Yuanlin, Wen Yuan, Xianfeng Chen, and Zhuangqi Cao. "Slow light over 1,000 fractional pulses based on ultrahigh-order guided modes in symmetrical metal-cladding optical waveguide." In CLEO: Applications and Technology. OSA, 2012. http://dx.doi.org/10.1364/cleo_at.2012.jw4a.1.
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Chen, Y. J., G. M. Carter, G. J. Sonek, and J. M. Ballantyne. "Nonlinear optical coupling to planar GaAs/AlGaAs waveguides." In Integrated and Guided Wave Optics. Optica Publishing Group, 1986. http://dx.doi.org/10.1364/igwo.1986.thcc6.
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Nonlinear optical interactions in waveguides utilizing the material’s third-order nonlinear optical susceptibility X(3) is of interest for potential application, such as ultrafast optical signal processing1 and nonlinear optical switching.2,3 The X(3) can significantly modify the coupling via either a prism or grating between a radiative wave and guided mode.3 Previously, the experimental demonstrations have been limited to either poor quality waveguides4 or materials with a slow (thermal) response time.5 We report both linear and nonlinear optical grating coupling to good quality planar GaAs/AlGaAs waveguides and demonstrated nonlinear optical switching. The planar waveguides used in the experiments (1.7-µm GaAs on 3.0-µm AlGaAs) were epitaxially grown by metal-organic chemical vapor deposition (MOCVD) techniques. A 3300-Å period sinusoidal grating of ≃500-Å amplitude was fabricated on the GaAs surface using holographic lithography and ion milling. The coupling to the guided modes was observed by monitoring the intensity of the reflected collimated beam as a function of incident angle. The propagation length of each waveguide mode was also measured by monitoring the output intensity at the cleaved edge of the waveguide as a function of the propagation distance (by moving the incident beam away from the cleaved edge). A cw mode-locked Q-switched Nd:YAG laser operating at 1.06 µm, which produced a mode-locked pulse train of 150-ps pulses, was the light source. The peak intensity of the unfocused optical pulses at the center of the pulse train is The peak intensity of the unfocused optical pulses at the center of the pulse train ≃1 MW/cm2, and the duration of the train is ≃300 ns.
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Ueda, T., K. Okamoto, J. Yamauchi, and T. Itoh. "Enhancement of Phase-Shifting Nonreciprocity in Metamate-rial Lines Loaded with Comb-Shaped Stubs Supporting Slow Wave Propagation of Edge Guided Modes." In 2018 IEEE International Magnetic Conference (INTERMAG). IEEE, 2018. http://dx.doi.org/10.1109/intmag.2018.8508634.
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Nucera, Claudio, and Francesco Lanza di Scalea. "Nonlinear Guided Waves for Structural Health Monitoring: Numerical Algorithm and Application to Railroad Track." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8139.
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The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is conducting research to develop a system for in-situ measurement of the rail Neutral Temperature in Continuous-Welded Rail (CWR). It is known that CWR can break in cold weather and can buckle in hot weather. Currently, there is a need for the railroads to know the current state of thermal stress in the rail, or the rail Neutral Temperature (rail temperature with zero thermal stress), to properly schedule slow-order mandates and prevent derailments. UCSD has developed a prototype for wayside rail Neutral Temperature measurement that is based on non-linear ultrasonic guided waves. Numerical models were first developed to identify proper guided wave modes and frequencies for maximum sensitivity to the thermal stresses in the rail web, with little influence of the rail head and rail foot. Experiments conducted at the Large-scale Rail NT Test-bed indicated a rail Neutral Temperature measurement accuracy of a few degrees. Field tests are planned at the Transportation Technology Center (TTC) in Pueblo, CO in June 2012 in collaboration with the Burlington Northern Santa Fe (BNSF) Railway.
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Nucera, Claudio, Robert Phillips, Francesco Lanza di Scalea, Mahmood Fateh, and Gary Carr. "A Wayside System for In-Situ Measurement of Rail Neutral Temperature by Nonlinear Ultrasonic Guided Waves." In ASME 2012 Rail Transportation Division Fall Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/rtdf2012-9407.
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The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is conducting research to develop a system for in-situ measurement of the rail Neutral Temperature in Continuous-Welded Rail (CWR). It is known that CWR can break in cold weather and can buckle in hot weather. Currently, there is a need for the railroads to know the current state of thermal stress in the rail, or the rail Neutral Temperature (rail temperature with zero thermal stress), to properly schedule slow-order mandates and prevent derailments. UCSD has developed a prototype for wayside rail Neutral Temperature measurement that is based on non-linear ultrasonic guided waves. Numerical models were first developed to identify proper guided wave modes and frequencies for maximum sensitivity to the thermal stresses in the rail web, with little influence of the rail head and rail foot. Experiments conducted at the Large-scale Rail NT Test-bed indicated a rail Neutral Temperature measurement accuracy of a few degrees. Field tests are planned at the Transportation Technology Center (TTC) in Pueblo, CO in June 2012 in collaboration with the Burlington Northern Santa Fe (BNSF) Railway.