| 51. |
- Genty, Goery, et al.
(författare)
-
Complete characterization of supercontinuum coherence
- 2011
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 28:9, s. 2301-2309
-
Tidskriftsartikel (refereegranskat)abstract
- Using second-order coherence theory of nonstationary light we examine in detail the coherence properties of supercontinuum radiation generated in nonlinear fibers. We show that the supercontinuum can be divided into quasi-coherent and quasi-stationary parts and that the relative contributions depend on the dynamics involved in the spectral broadening process. We establish the correspondence between the quasi-coherent part of the two-frequency correlation function of the second-order theory and the usual Dudley-Coen degree of coherence used to characterize the shot-to-shot stability of supercontinuum sources. Experimental implementation for measuring separately the quasi-coherent and quasi-stationary contributions is further addressed. Our results open the route for complete characterization of supercontinuum coherence.
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| 52. |
- Guo, Shuwei, et al.
(författare)
-
Optical surface transformation for reshaping the field intensity distribution
- 2016
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 33:9, s. 1847-1851
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we focus on how to reshape the field intensity distribution on the wavefront of an incident beam and produce special optical beams (e.g., asymmetric Gaussian beams, hollow beams, and zeroth-order Bessel beams) using optical surface transformation (OST). The key design method of this paper is based on OST, which is the extension of transformation optics. Numerical simulations are given to verify the performance of the proposed devices.
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| 53. |
- Hall, Björn, 1973, et al.
(författare)
-
Pump-probe collision in optical fibers : Four-wave-mixing induced frequency jump
- 2001
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America (OSA). - 0740-3224 .- 1520-8540. ; 18:11, s. 1652-1658
-
Tidskriftsartikel (refereegranskat)abstract
- An investigation is made of ultrafast pump-probe pulse collisions near the zero-dispersion wavelength in an optical single-mode fiber. A steplike probe frequency shift is observed when the pump power is gradually increased. The magnitude of this frequency jump is shown to depend on the phase difference between the pulses. This new effect is investigated numerically and experimentally and is attributed to four-wave mixing.
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| 54. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Frequency comb generation beyond the Lugiato-Lefever equation: multi-stability and super cavity solitons
- 2015
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 32:7, s. 1259-1266
-
Tidskriftsartikel (refereegranskat)abstract
- The generation of optical frequency combs in microresonators is considered without resorting to the mean-field approximation. New dynamical regimes are found to appear for high intracavity power that cannot be modeled using the Lugiato-Lefever equation. Using the Ikeda map, we show the existence of multi-valued stationary states and analyze their stability. Period doubled patterns are considered, and a novel type of super cavity soliton associated with the multi-stable states is predicted.
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| 55. |
- Hansson, Tobias, et al.
(författare)
-
Scalar Wigner theory for polarized light in nonlinear Kerr media
- 2013
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:6, s. 1765-1769
-
Tidskriftsartikel (refereegranskat)abstract
- A scalar Wigner distribution function for describing polarized light is proposed in analogy with the treatment of spin variables in quantum kinetic theory. The formalism is applied to the propagation of circularly polarized light in nonlinear Kerr media, and an extended phase-space evolution equation is derived along with invariant quantities. The formalism is additionally used to analyze the modulational instability. (C) 2013 Optical Society of America
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| 56. |
- Hansson, T., et al.
(författare)
-
Scalar Wigner theory for polarized light in nonlinear Kerr media
- 2013
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - : The Optical Society. - 1520-8540 .- 0740-3224. ; 30:6, s. 1765-1769
-
Tidskriftsartikel (refereegranskat)abstract
- A scalar Wigner distribution function for describing polarized light is proposed in analogy with the treatment of spin variables in quantum kinetic theory. The formalism is applied to the propagation of circularly polarized light in nonlinear Kerr media, and an extended phase-space evolution equation is derived along with invariant quantities. The formalism is additionally used to analyze the modulational instability
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| 57. |
- Hansson, Tobias, 1983, et al.
(författare)
-
Single envelope equation modeling of multi-octave comb arrays in microresonators with quadratic and cubic nonlinearities
- 2016
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 33:6, s. 1207-1215
-
Tidskriftsartikel (refereegranskat)abstract
- We numerically study, by means of the single envelope equation, the generation of optical frequency combs ranging from the visible to the mid-infrared spectral regions in resonators with quadratic and cubic nonlinearities. Phase-matched quadratic wave-mixing processes among the comb lines can be activated by low-power continuous wave pumping in the near infrared of a radially poled lithium niobate whispering gallery resonator. We examine both separate and coexisting intracavity doubly resonant second-harmonic generation and parametric oscillation processes and find that modulation instabilities may lead to the formation of coupled comb arrays extending over multiple octaves. In the temporal domain, the frequency combs may correspond to pulse trains or even to a single pulse circulating in the cavity.
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| 58. |
- Harvey, Clarissa M., 1988-, et al.
(författare)
-
Specialty optical fiber fabrication : fiber draw tower based on a CO laser furnace
- 2021
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society. - 0740-3224 .- 1520-8540. ; 38:12, s. F122-F129
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental, laboratory-scale optical fiber drawing tower based on CO laser heating has been developed and used to fabricate speciality optical fiber. The CO laser was utilized in a symmetric four beam heating system. The localized and responsive heating time of the laser-based furnace was beneficial for manufacturing crystalline core fibers, specifically, silicon core optical fibers. Moreover, the specific absorption properties of the CO laser radiation in silica have been evaluated with the aid of finite element modeling. In comparison to the more traditional CO2 laser, CO lasers were found to improve temperature uniformity and heating times while minimizing surface evaporation.
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| 59. |
- Hawkins, T. W., et al.
(författare)
-
Kilowatt power scaling of an intrinsically low Brillouin and thermo-optic Yb-doped silica fiber
- 2021
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 38:12, s. F38-F49
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of optical fibers is dependent on both the fiber design and the materials from which it is made. While much of the development over the past few decades has focused on fiber geometry and microstructuring, more recent analyses have shown clear benefits of addressing parasitic nonlinearities at the origins of their light–matter interactions. Reported here are results on intrinsically low Brillouin and thermo-optic core fibers, fabricated using modified chemical vapor deposition. Specifically, fibers in the Yb-doped Al2O3−P2O5−B2O3−SiO2 system are developed based on how each glass constituent affects the material parameters that enable both stimulated Brillouin scattering (SBS) and transverse mode instability (TMI). One fiber, developed to be very heavily doped, exhibited thermo-optic and Brillouin gain coefficients up to ∼3 dB and 6 dB below conventional laser fibers, respectively. A second fiber, designed to approximate a commercial double-clad laser fiber, which necessitated lower doping levels, was output power scaled to over 1 kW with an efficiency over 70% and no observed photodarkening under conventional testing. Design curves for the enabling material properties that drive TMI and SBS also are provided as functions of compositions as a tool for the community to further study and develop intrinsically low-nonlinearity fiber lasers.
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| 60. |
- Helgason, Òskar Bjarki, 1989, et al.
(författare)
-
Superchannel engineering of microcombs for optical communications
- 2019
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 36:8, s. 2013-2022
-
Tidskriftsartikel (refereegranskat)abstract
- Microresonator frequency combs (microcombs) are a promising technology for generating frequency carriers for wavelength division multiplexing (WDM) systems. Multi-terabit per second WDM coherent transmitters have recently been demonstrated using both dissipative Kerr solitons and mode-locked dark pulses in optical microresonators. These experiments have focused on microcombs designed to cover a large portion of the erbium-doped fiber window. However, the question of optimum bandwidth for microcombs in WDM systems has not been addressed. Here we show that segmenting the bandwidth into smaller microcomb-driven superchannels results in an improvement of power per line. Through numerical simulations we establish a quantitative comparison between dark-pulse and soliton microcombs in WDM systems, including aspects such as conversion efficiency, tolerance to intrinsic cavity loss, and group velocity dispersion engineering. We show that the improvement of minimum line power scales linearly with the number of superchannels for both types of microcombs. This work provides useful guidelines for the design of multi-terabit per second microcomb-based superchannel systems.
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| 61. |
- Holmberg, Patrik, 1971-, et al.
(författare)
-
Thermometric study of CO2-laser heated optical fibers in excess of 1700 degrees C using fiber Bragg gratings
- 2013
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:7, s. 1835-1842
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal response of optical fibers during CO2 laser irradiation has been characterized by using thermally stable short-period fiber Bragg gratings, referred to as chemical composition gratings. CO2 laser beam profiling was performed by scanning the beam across a 1 mm long grating, providing a spatial resolution given by the fiber diameter. The thermal dynamics during square pulse irradiation has been recorded for temperatures in excess of 1700°C, with heating and cooling rates as high as 10,500°C s−1 and 6500°C s−1, respectively.
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| 62. |
|
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| 63. |
- Jelger, Pär, et al.
(författare)
-
Degradation-resistant lasing at 980 nm in a Yb/Ce/Al-doped silica fiber
- 2010
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 27:2, s. 338-342
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we measure how photodarkening affects the optical efficiency for three different Yb/Al-doped silica fibers operating at 980 nm, one of which is codoped with cerium. A volume Bragg grating is used for linewidth control and added rejection of amplified spontaneous emission. Several hours of degradation-resistant operation is obtained with the Ce-codoped fiber, while for the Yb/Al doped fibers a large drop in efficiency is observed within the first hour of operation. Our results show that Yb/Ce/Al-doped fibers could be excellent candidates for high-power 980 nm fiber laser sources.
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| 64. |
- Jeong, H., et al.
(författare)
-
Evolution of Sommerfeld and Brillouin precursors in intermediate spectral regimes
- 2009
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 26:12, s. 2455-2460
-
Tidskriftsartikel (refereegranskat)abstract
- We study, numerically, the transitional behavior of precursors in the intermediate spectral regime between twocontrasting regimes for which analytical solutions exist. The two opposite regimes are, respectively, defined as(1) off-resonance carrier with a spectral pulse width comparable to the medium’s absorption linewidth and (2)on-resonance carrier with the spectral width of the pulse much narrower than the absorption linewidth. Beyondthese two regimes, there have been few studies of precursors. In this paper, we investigate precursordynamics for the intermediate spectral regime using the finite-difference time domain method. The parameterthat has the strongest influence on the precursor dynamics is found to be the plasma frequency, ωp. This researchis applicable for controlling transients in fast communication systems.
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| 65. |
- Jiao, Yuqing, et al.
(författare)
-
Accurate and efficient simulation for silicon-nanowire-based multimode interference couplers with a 3D finite-element mode-propagation analysis
- 2010
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of American (OSA). - 0740-3224 .- 1520-8540. ; 27:9, s. 1813-1818
-
Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional (3D) finite-element mode-propagation analysis is presented to give an accurate and efficient simulation for silicon-nanowire- based multimode interference (MMI) couplers. For the presented numerical method, a finite-element method mode solver is used to calculate the mode profiles and the propagation constants in a multimode section. The comparison between the presented method and some other numerical methods [e.g., finite-difference time-domain (FDTD) method, beam propagation methods, etc.] is also shown. It is shown that the presented numerical method gives simulation results very close to those from the 3D FDTD (with a deviation less than 1%). Therefore, it is very convenient for the design of Si-nanowire-based MMI couplers.
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| 66. |
- Johansson, Alexandra C., et al.
(författare)
-
Signal line shapes of Fourier-transform cavity-enhanced frequency modulation spectroscopy with optical frequency combs
- 2017
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 34:2, s. 358-365
-
Tidskriftsartikel (refereegranskat)abstract
- We present a thorough analysis of the signal line shapes of Fourier-transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS). We discuss the signal dependence on the ratio of the modulation frequency, f(m), to the molecular linewidth, G. We compare a full model of the signals and a simplified absorption-like analytical model that has high accuracy for low f(m)/G ratios and is much faster to compute. We verify the theory experimentally by measuring and fitting the NICE-OFCS spectra of CO2 at 1575 nm using a system based on an Er: fiber femtosecond laser and a cavity with a finesse of similar to 11000.
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| 67. |
- Jonsson, F., et al.
(författare)
-
Spectral windowing with chirped magneto-optical Bragg gratings
- 2005
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 22:1, s. 293-298
-
Tidskriftsartikel (refereegranskat)abstract
- We present a theory on a novel class of magneto-optical devices operated by means of magneto-optically induced refractive-index perturbations in chirped Bragg gratings. The predicted effect of the introduced perturbation is an opening of a narrow transmission window in the band-blocking transmission of the chirped grating. The narrow transmission window is tunable in wavelength, and relative transmission and the effects of multiple, spatially separated perturbations can also be superimposed, hence allowing for tunable, magneto-optically operated, multichannel add-drop multiplexors suitable for modularization in integrated optics.
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| 68. |
- Kabakova, Irina V., et al.
(författare)
-
Switching and dynamic wavelength conversion in a fiber grating cavity
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 29:1, s. 155-160
-
Tidskriftsartikel (refereegranskat)abstract
- Switching and dynamic wavelength conversion of light are demonstrated in a fiber grating cavity detuned by high-voltage electrical pulses. The cavity dynamics is studied using a heterodyne technique in which the frequency-shifted light, trapped by the cavity, mixes with the backreflected light at the incident frequency. We find that the frequency shift scales linearly with the energy of the electric driving pulses.
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| 69. |
- Karlsson, Magnus, 1967
(författare)
-
Four-wave mixing in fibers with randomly varying zero-dispersion wavelength
- 1998
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 15:8, s. 2269-2275
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of random fluctuations in the zero-dispersion wavelength is considered for fiber four-wave mixing. Theoretical expressions for average parametric gain, phase-conjugation conversion efficiency, and gain bandwidth are obtained and found to be in good agreement with experiments. Possible limitations on the noise figure in phase-sensitive amplifiers based on fiber four-wave mixing are also discussed.
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| 70. |
- Karlsson, Magnus, 1967
(författare)
-
Modulational instability in lossy optical fibers
- 1995
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 12:11, s. 2071-2077
-
Tidskriftsartikel (refereegranskat)abstract
- The modulational instability in an optical fiber, with loss taken into account, is analytically investigated. It is demonstrated how the linearized equation for perturbation can be solved exactly in terms of Bessel functions, and qualitative differences from previous analytic approaches are pointed out. Finally, the limits imposed by this instability on optical communication systems are discussed. The use of this theory in system design is examined.
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| 71. |
- Karlsson, Magnus, 1967, et al.
(författare)
-
Super-Gaussian approximation of the fundamental radial mode in nonlinear parabolic-index optical fibers
- 1992
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 9:9, s. 1558-1562
-
Tidskriftsartikel (refereegranskat)abstract
- Using a direct variational technique involving super-Gaussian trial functions, we find approximate solutions for the fundamental radial mode of an optical wave propagating in a nonlinear parabolic-index fiber. A detailed examination is made of the amplitude, width, radial profile, and longitudinal phase shift of the stationary solutions that represent a two-dimensional balance among diffraction, nonlinear self-focusing, and linear wave guiding. For pulse powers below the self-focusing power, the stationary solutions are stabilized by the parabolic index variation.
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| 72. |
- Karmstrand, Therese, 1989, et al.
(författare)
-
Successive quasienergy collapse and breakdown of photon blockade in the few-emitter limit
- 2024
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 41:8, s. C38-C47
-
Tidskriftsartikel (refereegranskat)abstract
- The emergent behavior that arises in many-body systems of increasing size follows universal laws that become apparent in order-to-disorder transitions. While this behavior has been traditionally studied for large numbers of emitters, recent progress allows for the exploration of the few-emitter limit, where correlations can be measured and connected to microscopic models to gain further insight into order-to-disorder transitions. We explore this few-body limit in the driven and damped Tavis–Cummings model, which describes a collection of atoms interacting with a driven and damped cavity mode. Our exploration revolves around the dressed states of the atomic ensemble and field, whose energies are shown to collapse as the driving field is increased to mark the onset of a dissipative quantum phase transition. The collapse occurs in stages and is an effect of light-matter correlations that are overlooked for single atoms and neglected in mean-field models. The implications of these correlations over the macroscopic observables of the system are presented. We encounter a shift in the expected transition point and an increased number of parity-broken states to choose from once the ordered phase is reached.
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| 73. |
- Khoptyar, D., et al.
(författare)
-
Experimental determination of the energy-transfer parameters for homogeneous upconversion in Er-doped silica
- 2005
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 22:10, s. 2091-2098
-
Tidskriftsartikel (refereegranskat)abstract
- Applying a nonlinear spectroscopic technique, we accurately monitor the dynamics of the homogeneous upconversion (HUC) in Er-doped fibers. We provide the first experimental confirmation, to our knowledge, of the earlier theoretical predictions that, for low erbium concentrations, a decay of HUC-influenced excitation probability of Er ions can be well approximated by the formula describing the static HUC. By correlating the experimentally obtained HUC dynamics with the results of our analytical model in a wide range of Er concentrations, we accurately estimate energy-transfer parameters for Er-doped silica glass and experimentally assess the validity of the model.
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| 74. |
- Khoptyar, D., et al.
(författare)
-
Homogeneous upconversion in Er-doped fibers under steady state excitation : analytical model and its Monte Carlo verification
- 2005
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 22:3, s. 582-590
-
Tidskriftsartikel (refereegranskat)abstract
- We present an extension to our earlier proposed statistical model for studying migration-assisted homogeneous upconversion in erbium-doped fibers. The extension takes into account minimum proximity distance between erbium ions randomly distributed in the host material and the nonuniformity of the excitation distribution among them. We derive a transcendental equation for the population inversion and find the dependence of the upconversion rate on the population inversion and the pump power for the entire range of feasible Er concentrations. We verify the validity and accuracy of the model by means of time-resolved Monte Carlo simulations.
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| 75. |
- Kockaert, Pascal, et al.
(författare)
-
Beyond the zero-diffraction regime in optical cavities with a left-handed material
- 2009
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 26:12, s. B148-B155
-
Tidskriftsartikel (refereegranskat)abstract
- The combination of right-handed and left-handed materials offers the possibility to design devices in which the mean diffraction is zero. Such systems are encountered, for example, in nonlinear optical cavities, where a true zero-diffraction regime could lead to the formation of patterns with arbitrarily small sizes. In practice, the minimal size is limited by nonlocal terms in the equation of propagation. We study the nonlocal properties of light propagation in a nonlinear optical cavity containing a right-handed and a left-handed material. We obtain a model for the propagation, including two sources of nonlocality: the spatial dispersion of the materials in the cavity, and the higher-order terms of the mean field approximation. We apply these results to a particular case and derive an expression for the parameter fixing the minimal size of the patterns.
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| 76. |
- Kolliopoulos, G., et al.
(författare)
-
Single-shot autocorrelator for extreme-ultraviolet radiation
- 2014
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 31:5, s. 926-938
-
Tidskriftsartikel (refereegranskat)abstract
- A novel single-shot second-order autocorrelation scheme for extreme-ultraviolet radiation (XUV) is proposed. It is based on an ion-imaging technique, which provides spatial information of ionization products in the focal volume of the XUV beam. Using simple analytical and detailed numerical modeling, an evaluation toward selecting an optimum configuration has been performed. The implementation of the concept to characterize attosecond pulses is discussed, and the proposed setups are assessed.
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| 77. |
- Korhonen, Minna, et al.
(författare)
-
Elementary field representation of supercontinuum
- 2013
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:1, s. 21-26
-
Tidskriftsartikel (refereegranskat)abstract
- We describe the second-order coherence functions of supercontinuum (SC) in terms of elementary fields that can be obtained from measurable average quantities. The representation is based on the partition of the second-order correlation functions of SC into quasi-coherent and quasi-stationary contributions. Numerical simulations of statistical ensembles of SC pulses with different coherence properties are used to illustrate the elementary field model. Comparison with the SC coherent-mode expansion is presented, and we also simulate the propagation of the elementary fields in a dispersive fiber to demonstrate the benefits of the model.
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| 78. |
|
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| 79. |
- Kröll, Stefan, et al.
(författare)
-
Recording Density Limit of Photon-echo Optical Storage With High-speed Writing and Reading
- 1993
-
Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:35, s. 7233-7242
-
Tidskriftsartikel (refereegranskat)abstract
- The first analysis to our knowledge of the optical data storage density of photon-echo storage is presented. Mainly considering signal-to-noise ratio performance, we calculate the obtainable storage density for data storage and processing using photon echoes to be approximately 100 times the theoretical limit for conventional optical data storage. This limit is similar to that theoretically calculated for data storage by use of persistent spectral hole burning. For storage times longer than the upper-state lifetime the highest densities can, however, be obtained only if all the excited atoms decay, or are transferred, to a different state than that from which they were originally excited. The analysis is restricted to samples with low optical density, and it also assumes that for every data sequence, writing is performed only once. It is therefore not directly applicable to accumulated photon echoes. A significant feature of photon-echo storage and processing is its speed; e.g., addressing 1 kbyte/(spatial point) permits terahertz read and write speeds for transitions with transition probabilities as low as 1000 s-1.
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| 80. |
- Lacy, R. A, et al.
(författare)
-
Photoionization-pumped gain at 185 nm in a laser-ablated indium plasma
- 1989
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 6:6, s. 1209-1216
-
Tidskriftsartikel (refereegranskat)abstract
- We reportwhat is to our knowledge the first production of gain by inner-shell photoionization of ions. Photoionization of 4d electrons from In$+$ ions created a population inversion on a 185-nm In2$+$ transition. This scheme is an isoelectronic scaling of the 442-nm Cd$+$ laser. A single-pass gain constant of 0.9 {\textpm} 0.3 cm{\textminus}1 over a 0.4-cm path was pumped by soft x rays generated by less than 50 mJ of 1.06-$\mu$m light focused onto a tantalum target. Laser ablation of a liquid-indium target provided a high density (1016 cm{\textminus}3) of ground-state In$+$ ions for this scheme. An indium amplified spontaneous emission laser and a synchronously pumped indium laser oscillator are proposed.
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| 81. |
- Laine, T. A., et al.
(författare)
-
Self-guided waves and exact solutions of the nonlinear Helmholtz equation
- 2000
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 17:5, s. 751-757
-
Tidskriftsartikel (refereegranskat)abstract
- The paraxial wave theory is known to lead to inaccurate predictions in self-focusing of optical beams. The nonlinear Helmholtz equation describes more accurately wave propagation in dispersive, spatially local, Kerr-type media. We derive rigorous bright and dark solutions to the nonlinear Helmholtz equation in a full three-dimensional form. These expressions are new and unique. The solutions are obtained with a multidimensional extension of the (paraxial) nonlinear Schrodinger equation. We also establish energy conservation laws for both nonlinear wave equations in terms of spatial currents. Our results give insight, for example, into the diffraction and breakup of tightly confined nonlinear fields.
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| 82. |
- Laine, T. A., et al.
(författare)
-
Thin-layer theory of nonlinear fields
- 2000
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 17:10, s. 1711-1715
-
Tidskriftsartikel (refereegranskat)abstract
- We derive a local nonlinear thin-layer theory for electromagnetic fields that propagate in layered structures of isotropic, dispersive, and spatially local Kerr media. By use of an ansatz of plane waves together with a thin-layer approximation, the two-dimensional Kerr-Maxwell equation is rigorously solved within a very thin slab, and the characteristic matrix of the nonlinear medium is determined. The theory makes use of periodicity and allows a direct calculation of the nonlinear field throughout the structure on the basis of the transmitted field. The method is applied in the two polarizations, TE and TM, and is illustrated with a numerical example. The nonlinear thin-layer technique provides a simple and accurate analytical theory that includes multiple plane-wave incident fields and takes rigorously into account all nonlinear interactions of these waves.
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| 83. |
- Laine, T. A., et al.
(författare)
-
Variational analysis and angular bistability in layered nonlinear Kerr media with phase conjugation
- 2000
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 17:6, s. 977-984
-
Tidskriftsartikel (refereegranskat)abstract
- The calculus of variations is applied to electromagnetic fields in a layered nonlinear structure supporting a guided wave. The system also includes a phase-conjugate mirror (PCM). By introducing a variational dimension and using a collection of plane waves as a trial function, we approximate the exact solution of the nonlinear Kerr-Maxwell equation. The formalism is new, and it involves the nonlinear interference of multiple plane waves. A simple analytical expression for the nonlinear field in the presence of the PCM is derived, and the fact that the scattered intensities may become bistable when the angle of incidence is varied is demonstrated. In particular, our theory predicts the angular bistability in the backscattering direction, where the effect of the guided waves is subtle. Our numerical results are also in good agreement with other theoretical approaches and with the experimental data.
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| 84. |
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| 85. |
- Lindberg, Robert, et al.
(författare)
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Simultaneous nonlinear wavelength and mode conversion for high-brightness blue sources
- 2021
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society. - 0740-3224 .- 1520-8540. ; 38:11, s. 3491-3498
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Tidskriftsartikel (refereegranskat)abstract
- We investigate frequency doubling of focused Bessel-like higher order fiber modes in a one-dimensionally quasi-phase matched structured KTP crystal. A single higher-order fiber mode, LP0,7, was generated at 971 nm using a fiber optical parametric amplifier pumped by sub-nanosecond pulses at 1064 nm. Frequency doubling to 485.5 nm was achieved with a maximum conversion efficiency of 48%, which produced a highly structured blue beam without any brightness improvement with respect to the fundamental beam. By optimizing the phase mismatch, we also experimentally demonstrate clean on-axis conversion-resulting from cascaded chi((2)) : chi((2)) processes, which is in good agreement with our numerical simulations, that give rise to brightness enhancement.
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| 86. |
- Liu, Yaqun, et al.
(författare)
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Type-II PPRKTP optical parametric oscillators in the 2 μm spectral range
- 2022
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optica Publishing Group. - 0740-3224 .- 1520-8540. ; 39:12, s. A36-A43
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally explored the design parameter space for periodically poled Rb : KTiOPO4 (PPRKTP) struc-tures in type-II optical parametric oscillators (OPOs) pumped at 1.064 mu m and operating in the 1.8-2.5 mu m range. This study identifies a set of Sellmeier expansions and thermooptic coefficients that can be used to accurately design the type-II PPRKTP structures in this spectral range. The performance of this OPO regime is investigated by employing different periodicities of PPRKTP, and the effective nonlinear coefficient is determined. Output at the mJ level with a bandwidth of better than 10 MHz is readily generated without optical damage. The temperature tuning rate of about 8 GHz/K of the central OPO frequency is substantially lower than in similar periodically poled lithium niobate devices and can be exploited for precise frequency tuning and easier thermal stabilization. The stimulated backward polariton scattering in the OPO cavities is also investigated and discussed.
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| 87. |
- Lundin, Richard
(författare)
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Dispersion flattening in a W fiber
- 1994
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 33:6, s. 14-1011
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Tidskriftsartikel (refereegranskat)abstract
- An exhaustive and simple method for dispersion flattening in double-clad single-mode fibers is presented. The idea is to generate all such fibers with a certain cutoff wavelength and then find, by one-dimensional minimization and direct inspection, fibers yielding minimum dispersion. As examples, the root mean square chromatic dispersion over the wavelength range (1.25, 1.60 mum) is minimized for a W fiber and also for a triangular-index fiber with a depressed inner cladding. The material dispersion is included through a Sellmeier refractive-index formula. The full vector solution of Maxwell's equations is used. It is found, as is well known, that the W fiber is capable of dispersion flattening. The validity of the numerical results presented depends on the validity of the approximate refractive-index model used.
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| 88. |
- Lundin, Richard
(författare)
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Minimization of the chromatic dispersion over a broad wavelength range in a single-mode optical fiber
- 1993
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:18, s. 45-3241
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Tidskriftsartikel (refereegranskat)abstract
- The effective refractive index as a function of vacuum wavelength is approximated by Lagrange interpolation polynomials. The rms value of the chromatic dispersion is then calculated analytically. It is demonstrated that use of fourth-degree polynomials is far more efficient than the use of second-degree polynomials. The rms value of the chromatic dispersion over the wavelength range (1.25 mum, 1.60 mum) is calculated and minimized for step-index fibers, triangular index fibers, and alpha-power fibers. The full vector solution of Maxwell's equations is used. The error induced by the approximate refractive-index model is found to be negligible at the point of minimum dispersion.
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| 89. |
- Maccaferri, Nicolò, Dr. 1988-
(författare)
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Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities : an overview on properties and applications [Invited]
- 2019
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Ingår i: Journal of the Optical Society of America B. - : Optica Publishing Group. - 0740-3224 .- 1520-8540. ; 36:7, s. E112-E131
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Forskningsöversikt (refereegranskat)abstract
- We review the fundamental aspects and applications of functional magneto-optic and opto-magnetic metamaterials displaying collective and coupling effects on the nanoscale, where the concepts of optics and magnetism merge to produce unconventional phenomena. The use of magnetic materials instead of the usual noble metals allows for an additional degree of freedom for the control of electromagnetic field properties as well as allowing light to interact with the spins of the electrons and to actively manipulate the magnetic properties of such nanomaterials. In this context, we explore the concepts of near-field coupling of plasmon modes in magnetic metamolecules as well as the effect of excitation of surface lattice resonances in magneto-plasmonic crystals. Moreover, we discuss how these coupling effects can be exploited to artificially enhance optical magnetism in plasmonic metamolecules and crystals. Finally, we highlight some of the present challenges and provide a perspective on future directions of the research toward photon-driven fast and efficient nanotechnologies bridging magnetism and optics beyond current limits.
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| 90. |
- Major, Balázs, et al.
(författare)
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Effect of plasma-core-induced self-guiding on phase matching of high-order harmonic generation in gases
- 2019
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 36:6, s. 1594-1601
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we numerically study a self-guiding process in which ionization plays a dominant role and analyze its effect on high-order harmonic generation (HHG) in gases. Although this type of self-guiding-termed "plasmacore- induced self-guiding" in previous works-limits the achievable cutoff by regulating the intensity of the laser beam, it provides favorable conditions for phase matching, which is indispensable for high-flux-gas highharmonic sources. To underline the role of self-guiding in efficient HHG, we investigate the time-dependent phase-matching conditions in the guided beam and show how the spatiotemporally constant fundamental intensity contributes to the constructive buildup of the harmonic field in a broad photon energy range up to the provided cutoff.
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| 91. |
- Malomed, B. A., et al.
(författare)
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Propagation of an optical pulse in a fiber link with random-dispersion management
- 2001
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America (OSA). - 0740-3224 .- 1520-8540. ; 18:9, s. 1243-1251
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Tidskriftsartikel (refereegranskat)abstract
- A model of a long optical communication line consisting of alternating segments with anomalous and normal dispersion, whose lengths are picked randomly from a certain interval, is considered. As the first stage of the analysis, we calculate small changes in parameters of a quasi-Gaussian pulse passing a double-segment cell by means of the variational approximation (VA) and we approximate the evolution of the pulse passing many cells by smoothed ordinary differential equations with random coefficients, which are solved numerically. Next we perform systematic direct simulations of the model. Simulations reveal slow long-scale dynamics of the pulse, frequently in the form of long-period oscillations of its width. It is thus found that the soliton is most stable in the case of zero path-average dispersion (PAD), less stable in the case of anomalous PAD, and least stable in the case of normal PAD. The soliton's stability also strongly depends on its energy, the soliton with low energy being much more robust than its high energy counterpart.
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| 92. |
- Miranda, Miguel, et al.
(författare)
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Fast iterative retrieval algorithm for ultrashort pulse characterization using dispersion scans
- 2017
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 34:1, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- We present an iterative retrieval algorithm based on data constraint for ultrashort pulse characterization using dispersion scan (d-scan). The proposed algorithm is much faster and leads to a drastic reduction of retrieval times, but, compared to the standard algorithm, it performs less robustly in the retrieval of noisy d-scan traces. The algorithm is tested on several simulated cases and in two different experimental cases in the few-cycle regime.
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| 93. |
- Myrén, Niklas, et al.
(författare)
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In-fiber electrode lithography
- 2004
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 21:12, s. 2085-2088
-
Tidskriftsartikel (refereegranskat)abstract
- The fabrication of meter-long continuous internal fiber electrodes is achieved through deposition of a silver film inside a twin-hole fiber. Photolithography of the electrodes with 5-μm resolution inside the fiber is demonstrated by point-by-point side exposure to 0.53-μm radiation through the unharmed acrylate coating, causing laser ablation. A proof-of-principle experiment demonstrates the creation of a phase-matched structure for frequency doubling.
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| 94. |
- Oriekhov, Taras, et al.
(författare)
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Specialty optical fiber fabrication : preform manufacturing based on asymmetrical CO laser heating
- 2021
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society. - 0740-3224 .- 1520-8540. ; 38:12, s. F130-F137
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Tidskriftsartikel (refereegranskat)abstract
- Here, we present an innovative preform manufacturing technique for specialty optical fibers based on a carbon monoxide laser heating a rotating preform. The setup performance is evaluated with the aid of finite element modeling. The fabrication process is described in detail using silicon core preforms as a benchmark. The hybrid material nature of such a preform is addressed, together with the relevant characteristics, such as the difference in thermal conductivity and thermal expansion. Silicon core preforms with a wide range of core sizes were manufactured, proving the viability of this system for the development of specialty optical fibers based on novel materials.
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| 95. |
- Pitois, C., et al.
(författare)
-
Absorption and scattering in low-loss polymer optical waveguides
- 2001
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 18:7, s. 908-912
-
Tidskriftsartikel (refereegranskat)abstract
- The absolute absorption spectra of low-loss optical waveguides, together with their intrinsic and extrinsic scatterings, were measured in the near infrared. Photothermal deflection spectroscopy was used to measure the full absorption spectra of a series of fluorinated cross-linked polymers. Assignment of-CH3,-CH2-, and -OH overtones as well as of combinations of overtones were made by use of the theory of anharmonic vibrations based on a Morse potential for local modes. Details of the molecular potential are given. The total attenuation in slab waveguides made with these polymers was measured by a prism-coupling technique and compared with the absolute absorption. Losses that are due to the material itself and those that are due to the processing are quantified.
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| 96. |
- Prawiharjo, Jerry, et al.
(författare)
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Frequency-resolved optical gating in the 1.55 um band via cascaded chi-2 processes
- 2005
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 22:9, s. 1985-1993
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate ultrashort-pulse interactions based on cascaded second-harmonic generation and difference-frequency generation and propose their use for frequency-resolved optical gating (FROG) at telecom wavelengths in a waveguide configuration. We show how a chi((2))-chi((2)) FROG device could allow the efficient characterization of ultrashort pulses, with time resolutions well beyond the limits normally imposed by walk-off effects on single-step chi((2)) FROG devices.
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| 97. |
- Qiu, Min, et al.
(författare)
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Optimal design of a two-dimensional photonic crystal of square lattice with a large complete two-dimensional bandgap
- 2000
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 17:6, s. 1027-1030
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Tidskriftsartikel (refereegranskat)abstract
- Optimal design of a two-dimensional photonic crystal with a square lattice of air holes in GaAs is considered. It is shown how a maximum complete two-dimensional band gap is obtained by optimally connecting the dielectric rods with veins. The complete two-dimensional bandgap of our optimal design reaches Delta omega = 0.0762(2 pi c/a) (a is the lattice constant).
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| 98. |
- Quiroga-Teixeiro, M. L., et al.
(författare)
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Compression of optical solitons by conversion of nonlinear modes
- 1995
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 12:6, s. 1110-1116
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Tidskriftsartikel (refereegranskat)abstract
- One can transform an optical pulse containing higher-order soliton modes and/or radiation modes into a compressed almost ideal single-soliton pulse by passing it through an initial adaptive fiber of suitably chosen length and dispersion. Analytical approximations, in good agreement with numerical simulations, are found for the optimal values of the length and the dispersion of the adaptive fiber. The technique is applied to the case of nonadiabatically amplified soliton pulses, for which the transformation is shown to result in efficiently compressed soliton pulses.
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| 99. |
- Quiroga-Teixeiro, M. L., et al.
(författare)
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Efficient soliton compression by fast adiabatic amplification
- 1996
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Soc of America. - 0740-3224 .- 1520-8540. ; 13:4, s. 687-692
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Tidskriftsartikel (refereegranskat)abstract
- This paper shows the possibility of obtaining fast, but still adiabatic, amplification of soliton pulses by using a rapidly increasing distributed amplification with scale lengths comparable with the characteristic dispersion length. Explicit expressions for the required distribution of this gain and the variation of the pulse width are given, and theoretical predictions have been verified by numerical simulations. The practical implementation of the compression scheme should be possible by using an active fiber with a doping proportional to the required gain distribution. A study was also made of how efficient compression of solitons can be obtained.
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| 100. |
- Quiroga-Teixeiro, M. L., et al.
(författare)
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Internal dynamics of nonlinear beams in their ground states : Short- and long-lived excitation
- 1999
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America (OSA). - 0740-3224 .- 1520-8540. ; 16:10, s. 1697-1704
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the dynamics of optical beams in a cubic (focusing)-quintic (defocusing) nonlinear medium. In particular, we have found that strong beams can show long-lived elliptical oscillations, whereas in other cases, i.e., for weak beams or cylindrical oscillations, the dynamics decay quickly. This finding explains the observed higher efficiency in the fusion of two strong beams. We have also investigated, numerically and analytically, the robustness of the beams to an initial phase chirp.
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