Academic literature on the topic 'Spectral degeneracy'

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Journal articles on the topic "Spectral degeneracy"

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Ceulemans, A., E. Lijnen, P. W. Fowler, R. B. Mallion, and T. Pisanski. "Graph theory and the Jahn–Teller theorem." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, no. 2140 (2011): 971–89. http://dx.doi.org/10.1098/rspa.2011.0508.

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The Jahn–Teller (JT) theorem predicts spontaneous symmetry breaking and lifting of degeneracy in degenerate electronic states of (nonlinear) molecular and solid-state systems. In these cases, degeneracy is lifted by geometric distortion. Molecular problems are often modelled using spectral theory for weighted graphs, and the present paper turns this process around and reformulates the JT theorem for general vertex- and edge-weighted graphs themselves. If the eigenvectors and eigenvalues of a general graph are considered as orbitals and energy levels (respectively) to be occupied by electrons,
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Марков, Ю. Ф., В. Н. Гурин та К. В. Понкратов. "Рамановское рассеяние кристаллами гексаборидов редких земель с различными изотопами бора". Физика твердого тела 60, № 4 (2018): 715. http://dx.doi.org/10.21883/ftt.2018.04.45681.282.

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AbstractMonocrystals of lanthanum hexaboride LaB_6 containing both natural boron and its isotopes ^10B and ^11B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the re
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Zhang, Shuo, Hua-Wei Zhang, Georges Comte, et al. "M Subdwarf Research. III. Spectroscopic Diagnostics for Breaking Parameter Degeneracy." Astrophysical Journal 942, no. 1 (2023): 40. http://dx.doi.org/10.3847/1538-4357/aca28d.

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Abstract To understand the parameter degeneracy of M subdwarf spectra at low resolution, we assemble a large number of spectral features in the wavelength range 0.6–2.5 μm with band strength quantified by narrowband indices. Based on the index trends of BT-Settl model sequences, we illustrate how the main atmospheric parameters (T eff, log g, [M/H], and [α/Fe]) affect each spectral feature differently. Furthermore, we propose a four-step process to determine the four parameters sequentially, which extends the basic idea proposed by Jao et al. Each step contains several spectral features that b
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Byrohl, C., та M. Gronke. "Variations in shape among observed Lyman-α spectra due to intergalactic absorption". Astronomy & Astrophysics 642 (жовтень 2020): L16. http://dx.doi.org/10.1051/0004-6361/202038685.

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Lyman-α (Lyα) spectra provide insights into the small-scale structure and kinematics of neutral hydrogen (HI) within galaxies as well as the ionization state of the intergalactic medium (IGM). The former defines the intrinsic spectrum of a galaxy, which, in turn, is modified by the latter. These two effects are degenerate. Using the IllustrisTNG100 simulation, we studied the impact of the IGM on Lyα spectral shapes between z ∼ 0 and 5. We computed the distribution of the expected Lyα peaks and of the peak asymmetry for different intrinsic spectra, redshifts, and large-scale environments. We fi
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Rickard, M. J., R. Hainich, D. Pauli, et al. "Determining stellar properties of massive stars in NGC346 in the SMC with a Bayesian statistic technique." Astronomy & Astrophysics 692 (December 2024): A149. https://doi.org/10.1051/0004-6361/202450033.

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Context. NGC 346 is a young cluster with numerous hot OB stars. It is part of the Small Magellanic Cloud (SMC), and has an average metallicity that is one-seventh of the Milky Way’s. A detailed study of its stellar content provides a unique opportunity to understand the stellar and wind properties of massive stars in low-metallicity environments, and enables us to improve our understanding of star formation and stellar evolution. Aims. The fundamental stellar parameters defining a star’s spectral appearance are its effective surface temperature, surface gravity, and projected rotational veloci
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Ilyashenko, Alla, and Sergey Kuznetsov. "On degeneracy of dispersive waves at the bulk wave velocities." E3S Web of Conferences 97 (2019): 03004. http://dx.doi.org/10.1051/e3sconf/20199703004.

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Degeneracy of the linear dispersion wave equation at the phase velocities coinciding with the bulk wave velocities is observed and analysed. Spectral analysis of Pochhammer – Chree equation is performed. The corrected analytical solutions for components of the displacement fields are constructed, accounting degeneracy of the secular equations and the corresponding solutions.
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Chouaou, Fatiha, Chahira Aichi, and Abbes Benaissa. "Decay estimates for a degenerate wave equation with a dynamic fractional feedback acting on the degenerate boundary." Filomat 35, no. 10 (2021): 3219–39. http://dx.doi.org/10.2298/fil2110219c.

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In this paper, we consider a one-dimensional weakly degenerate wave equation with a dynamic nonlocal boundary feedback of fractional type acting at a degenerate point. First We show well-posedness by using the semigroup theory. Next, we show that our system is not uniformly stable by spectral analysis. Hence, we look for a polynomial decay rate for a smooth initial data by using a result due Borichev and Tomilov which reduces the problem of estimating the rate of energy decay to finding a growth bound for the resolvent of the generator associated with the semigroup. This analysis proves that t
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Fedorova, Elena, Lidiia Zadorozhna, Anatolii Tugay, Nadiia Pulatova, Alexander Ganz, and Olexandr Gugnin. "Separating the Spectral Counterparts in NGC 1275/Perseus Cluster in X-Rays." Astronomy 3, no. 4 (2024): 275–88. http://dx.doi.org/10.3390/astronomy3040017.

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We present a model-independent method for separating the spectral counterparts of the active galactic nucleus (AGN) NGC 1275 from the surrounding emission of the Perseus cluster, as observed by Suzaku/XIS cameras. The Perseus cluster emission extends to higher energies than typically observed in AGN environments, reaching up to 9–10 keV. This necessitates precise separation of AGN and cluster spectra. To circumvent the degeneracy arising from numerous spectral fitting parameters, including elemental abundances, thermal and Compton emissions from the nucleus, and spectral parameters of the jet
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Sarkar, Shilpa, Indranil Chattopadhyay, and Philippe Laurent. "Two-temperature solutions and emergent spectra from relativistic accretion discs around black holes." Astronomy & Astrophysics 642 (October 2020): A209. http://dx.doi.org/10.1051/0004-6361/202037520.

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Aims. We investigate a two-temperature advective transonic accretion disc around a black hole and analyse its spectrum in the presence of radiative processes such as bremsstrahlung, synchrotron, and inverse-Comptonisation. The aim is to link the emergent spectra with constants of motion of the accretion disc fluid, however, the number of unknowns in two-temperature theory exceeds the number of equations for a given set of constants of motion. We intend to remove the degeneracy using a general methodology and obtain a unique solution, along with its spectrum. Methods. We used hydrodynamic equat
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Jagod, Mary-Frances, Charles M. Gabrys, Matthias Rösslein, Dairene Uy, and Takeshi Oka. "Infrared spectrum of CH3+ involving high rovibrationai levels." Canadian Journal of Physics 72, no. 11-12 (1994): 1192–99. http://dx.doi.org/10.1139/p94-153.

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An extensive search of carbo-ion spectra in the infrared region from 3300 cm−1 to 2900 cm−1 has revealed many spectral lines of CH3+, the most fundamental hydrocarbon cation. Out of over 1000 spectral lines that were identified as due to CH3+from their plasma chemical behaviors and linewidths, 356 lines have been assigned to the CH stretch ν3 fundamental band. Most of the remaining lines are thought to belong to the hot bands ν2 + ν3 − ν2 and ν3 + ν4 − ν4. Their analysis was found to be difficult because of the large Coriolis interaction and the near degeneracy of ν2 and ν4. A series of spectr
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Dissertations / Theses on the topic "Spectral degeneracy"

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Stakhursky, Vadim Leonidovich. "Vibronic structure and rotational spectra of radicals in degenerate electronic state. Case of CH₃O and asymmetrically deuterated isotopomers (CHD₂O and CH₂DO) /." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1117634691.

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Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xv, 323 p.; also includes graphics (some col.) Includes bibliographical references. Available online via OhioLINK's ETD Center
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Miti, Filippo. "Mathematical models for cellular aggregation: the chemotactic instability and clustering formation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12020/.

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In this thesis we present a mathematical formulation of the interaction between microorganisms such as bacteria or amoebae and chemicals, often produced by the organisms themselves. This interaction is called chemotaxis and leads to cellular aggregation. We derive some models to describe chemotaxis. The first is the pioneristic Keller-Segel parabolic-parabolic model and it is derived by two different frameworks: a macroscopic perspective and a microscopic perspective, in which we start with a stochastic differential equation and we perform a mean-field approximation. This parabolic model may b
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Stakhursky, Vadim L. "Vibronic structure and rotational spectra of radicals in degenerate electronic state. Case of CH3 O and asymmetrically deuterated isotopomers (CHD2 O and CH2 DO)." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1117634691.

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Faure, Frédéric. "Approche géométrique de la limite semi-classique par les états cohérents et mécanique quantique sur le tore." Grenoble 1, 1993. http://www.theses.fr/1993GRE10188.

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Cette these est consacree a des problemes lies a l'etude de la limite semi-classique en mecanique quantique. Le premier chapitre presente une formulation geometrique qui est equivalente au principe variationnel. Elle consiste a concevoir la dynamique classique comme une projection orthogonale de la dynamique quantique sur la famille des etats coherents. L'angle de la projection nous renseigne sur la validite de l'approximation obtenue. Ces resultats sont illustres par un exemple numerique. Le deuxieme chapitre s'attache a la mecanique quantique sur le tore en tant qu'espace de phase, et en par
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Biarnés, Pérez Marc 1973. "Increased fundus autofluorescence, a biomarker of lipofuscin content, as a risk factor for the progression of geographic atrophy secondary to age-related macular degeneration." Doctoral thesis, Universitat Pompeu Fabra, 2014. http://hdl.handle.net/10803/318157.

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L’atròfia geogràfica (AG) és la variant avançada de la degeneració macular associada a l’edat seca i es caracteritza per la presència d’àrees d’atròfia de l’epiteli pigmentari de la retina (EPR) que creixen progressivament, amb pèrdua secundària dels fotorreceptors i la coriocapilar adjacents. Actualment és una condició sense tractament. L’acumulació de lipofuscina a l’EPR, visualitzable clínicament mitjançant l’autofluorescència del fons d’ull (AFU) com a zones d’elevada autofluorescència, ha estat vinculada a la progressió de l’AG en alguns estudis. De fet, s’han descrit certs patrons (“fen
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Books on the topic "Spectral degeneracy"

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1943-, Gossez J. P., and Bonheure Denis, eds. Nonlinear elliptic partial differential equations: Workshop in celebration of Jean-Pierre Gossez's 65th birthday, September 2-4, 2009, Université libre de Bruxelles, Belgium. American Mathematical Society, 2011.

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Horing, Norman J. Morgenstern. Graphene. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198791942.003.0012.

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Chapter 12 introduces Graphene, which is a two-dimensional “Dirac-like” material in the sense that its energy spectrum resembles that of a relativistic electron/positron (hole) described by the Dirac equation (having zero mass in this case). Its device-friendly properties of high electron mobility and excellent sensitivity as a sensor have attracted a huge world-wide research effort since its discovery about ten years ago. Here, the associated retarded Graphene Green’s function is treated and the dynamic, non-local dielectric function is discussed in the degenerate limit. The effects of a quan
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Book chapters on the topic "Spectral degeneracy"

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Brylinski, Jean-Luc. "The Degeneracy of Two Spectral Sequences." In The Gelfand Mathematical Seminars, 1990–1992. Birkhäuser Boston, 1993. http://dx.doi.org/10.1007/978-1-4612-0345-2_1.

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Levendorskii, Serge. "Spectral Asymptotics of Degenerate Elliptic Operators." In Degenerate Elliptic Equations. Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-1215-6_11.

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Levendorskii, Serge. "Spectral Asymptotics of Hypoelliptic Operators with Multiple Characteristics." In Degenerate Elliptic Equations. Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-1215-6_12.

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Levendorskii, Serge. "General Schemes of Investigation of Spectral Asymptotics for Degenerate Elliptic Equations." In Degenerate Elliptic Equations. Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-1215-6_10.

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Truc, Françoise. "Eigenvalue Asymptotics for Magnetic Fields and Degenerate Potentials." In Spectral Theory and Analysis. Springer Basel, 2011. http://dx.doi.org/10.1007/978-3-7643-9994-8_9.

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Lewis, Roger T. "Spectral Properties of Some Degenerate Elliptic Differential Operators." In Spectral Theory, Function Spaces and Inequalities. Springer Basel, 2011. http://dx.doi.org/10.1007/978-3-0348-0263-5_9.

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Ospanov, Kordan N. "Spectral Properties of Degenerate High-Order Differential Operator." In Springer Proceedings in Mathematics & Statistics. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-67053-9_27.

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Adamyan, Vadim, Reinhard Mennicken, and Vjacheslav Pivovarchik. "On the Spectral Theory of Degenerate Quadratic Operator Pencils." In Recent Advances in Operator Theory. Birkhäuser Basel, 2001. http://dx.doi.org/10.1007/978-3-0348-8323-8_1.

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Chi, M. Y., and Qi Minyou. "A Unified Approach to the Theory of Fundamental Solutions, Non-degenerate Case." In Partial Differential Equations and Spectral Theory. Birkhäuser Basel, 2001. http://dx.doi.org/10.1007/978-3-0348-8231-6_9.

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Haken, Hermann, and Hans Christoph Wolf. "Lifting of the Orbital Degeneracy in the Spectra of Alkali Atoms." In Advanced Texts in Physics. Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-98099-2_11.

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Conference papers on the topic "Spectral degeneracy"

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Shen, Yichen, Sashank K. Sridhar, Grégory Moille, Fahad A. Shaikh, Kartik Srinivasan, and Avik Dutt. "Nonequilibrium Phase Transitions in a Dual-pumped Silicon Nitride Kerr Optical Parametric Oscillator." In CLEO: Science and Innovations. Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_si.2024.sw4f.2.

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We demonstrate spectral phase transitions in dual-pumped Si3N4 nanophotonic Kerr optical parametric oscillators with anomalous dispersion. Through pump-power modulation, we observe real-time switching between a near-degenerate signal (0-FSR separation) and non-degenerate signals (4-FSR separation).
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Swillo, Marcin, Patrick Mutter, Albert Peralta Amores, Andrius Zukauskas, and Valdas Pasiskevicius. "Counter-directional generation of photon-pairs in periodically poled Rb-KTiOPO4." In CLEO: Fundamental Science. Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_fs.2024.ff1k.1.

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For the first time, we show spectral and polarization indistinguishability of photon pairs generated in counter-propagating degenerate spontaneous parametric downconversion in the telecommunications band using first-order quasi-phase-matching in periodically poled Rb-KTiOPO4.
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Sanchez, A. D., S. Chaitanya Kumar, and M. Ebrahim-Zadeh. "Femtosecond pulse generation from a cw-driven degenerate optical parametric oscillator." In CLEO: Applications and Technology. Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_at.2024.jw2a.179.

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We describe a novel configuration of bulk χ (2) OPO providing near-transform-limited sub-100 fs pulses with coherent broadband phase-locked spectrum when driven with a cw laser by deploying an intracavity electro-optic-modulator together with dispersion control.
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Takeya, Kei, Vincent Yahia, Hideki Ishizuki, and Takunori Taira. "Amplification of narrow linewidth 2-wavelength light for THz wavelength conversion." In Advanced Solid State Lasers. Optica Publishing Group, 2024. https://doi.org/10.1364/assl.2024.jw2a.16.

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In generation of high-intensity terahertz (THz) waves, the difference frequency generation (DFG) method is a promising approach, but there are challenges such as wavelength selection of the excitation light, spectral width, and the scaling of the light source. To address these issues, we used a degenerate optical parametric system with a multiple reflection Bragg diffraction grating (VBG) to convert the 1064 nm light from an Nd:YAG micro MOPA into two wavelengths, 2126 nm and 2130 nm, with a linewidth of less than 1 nm. We also confirmed the generation of THz waves using this light and demonst
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Trommsdorff, H. Peter, Christoph Rambaud, François Ramaz, and Jean-Claude Vial. "Coupled Proton Tunneling Systems: Observation of Ultraslow Relaxation Phenomena." In Spectral Hole-Burning and Luminescence Line Narrowing: Science and Applications. Optica Publishing Group, 1992. http://dx.doi.org/10.1364/shbl.1992.tuc2.

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Tunneling phenomena manifest itself essentially in two different ways. One is the displacement of particles across energy barriers without the need of thermal activation. This is a relaxation phenomenon and accounts for the occurrence of chemical reactions at 0 K and the evolution of glasses which continues at the lowest temperatures and leads to such observations as spectral diffusion. The other is the splitting of energy levels in a potential having several identical minima. This splitting lifts the degeneracy of states which describe the particle localized in one of the (isolated) wells. Th
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Nebel, A., and R. Beigang. "Ultrashort pulse generation by internal pulse compression of synchronously pumped optical parametric oscillators at degeneracy." In Nonlinear Optics. Optica Publishing Group, 1992. http://dx.doi.org/10.1364/nlo.1992.mc5.

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Synchronously pumped cw mode locked optical parametric oscillators (OPO) are ideal sources for tunable ultrashort pulses in the visible and near infrared spectral region. They can be tuned over a wide wavelength range and picosecond and sub-picosecond pulses have been obtained already with substantial average and peak powers [1,2].
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Nebel, A., U. Socha, and R. Beigang. "Cw mode locked singly resonant optical parametric oscillator pumped by a Ti: sapphire laser." In International Conference on Ultrafast Phenomena. Optica Publishing Group, 1992. http://dx.doi.org/10.1364/up.1992.thc1.

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Optical parametric oscillators (OPO) are ideal sources of tunable radiation in the near uv, visible and infrared spectral region. Synchroneously pumped OPOs can generate tunable picosecond and femtosecond pulses. However, most of these systems have to be pumped with a mode locked and Q—switched pump laser1 or even intracavity of the pump source2 in order to overcome oscillation threshold. Recently a cw mode locked OPO was operated near degeneracy in KTiOPO4 (KTP) when pumped with the frequency doubled radiation of a self mode locked Nd:YLF laser.3 The operation in an extracavity configuration
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Koch, P., F. Ruebel, M. Nittmann, T. Bauer, J. Bartschke, and J. A. L’huillier. "Influence of the Spectral Properties of the Pump Laser on the Behaviour of an Optical Parametric Oscillator with a Volume Bragg Grating Output Coupler around Degeneracy." In Nonlinear Photonics. OSA, 2010. http://dx.doi.org/10.1364/np.2010.nthc2.

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Idell, Paul S. "Optimal imaging concentrators based on the ratio of encircled energy criterion." In OSA Annual Meeting. Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.thh1.

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We investigate the effects of spatial coherence on the design of optimal imaging concentrators where the ratio of encircled energy (REE) in the image plane is used to gauge concentrator performance. Using the REE criterion, we develop an apodization procedure which provides optimal light concentration for source fields possessing arbitrary states of spatial coherence and for arbitrary detector configurations. Our solution for the optimal pupil screen invokes the use of a generalized Fredholm-type integral equation whose integral kernel (and weighting function) are determined by the pupil field
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Chyba, D. E., Neal B. Abraham, and A. M. Albano. "Stability and time-dependent behavior of the detuned ring laser with a saturable absorber in the vicinity of multiple steady-state solutions." In OSA Annual Meeting. Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.fw3.

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We present an examination of the stability and time-dependent behavior of a semiclassical model of the ring laser with a saturable absorber, in the vicinity of multiple steady-state solutions. We consider particularly the case in which the cavity is tuned away from the resonance frequency of the gain medium. The model considers the absorbing and amplifying media to consist of two-level atoms. Only homogeneous spectral broadening and unidirectional propagation of the light are considered. We are able to treat the steady state with an approximate mean field solution and also with its exact longi
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