Search results for "Linea"

The role of mothers' beliefs in students' self-concept of ability development

2018

The aim of this study was to investigate whether the child-related competence beliefs of mothers are associated with the development of Finnish adolescents' self-concept of mathematics and literacy ability during their transition from primary to lower secondary school and whether these associations depend on adolescents' level of performance. The results showed that, first, adolescents' self-concept of mathematics and literacy ability decreased over time. The impact of maternal beliefs on the linear trend of the self-concept of mathematics and literacy ability was dependent on the level of students' performance. Mothers' high beliefs buffered against the decrease in adolescents' self-concep…

Matriisin Hessenbergin muoto

2013

Modeling epidemics through ladder operators

2020

Highlights • We propose an operatorial model to describe epidemics. • The model describes well the asymptotic numbers of the epidemics. • Ladder operators are used to model exchanges between the “actors” of the system.

Experimental investigation of the optical Kerr effect at large laser intensity: impact on the propagation of a short and intense laser pulse

2010

Talk given by O. Faucher; International audience

Negative and positive Kerr nonlinearity of air calibrated with transient molecular alignment

2009

Talk given by O. Faucher; International audience; Nonlinear electronic Kerr index of the major air constituents has been measured up to high order terms using transient molecular alignment as a reference. Sign reversal associated to negative nonlinearity is observed above a pulse intensity of 26 TW/cm^.2

Higher-order Kerr terms allow ionization-free filamentation in gases

2010

Talk given by J. Kasparian; International audience; Higher-order nonlinear indices, rather than plasma, provide the main defocusing contribution to filamentation in gases at 800 nm. Developing generalized Miller formulae, we discuss the generality of this as a function of the laser wavelength

Measurement of nonlinear and chromatic dispersion parameters of optical fibers using modulation instability

2006

International audience; We present a simple method for the measurement of Kerr, second- and third-order dispersion coefficients in optical fibers using power and dispersion dependences of modulation instability near the zero-dispersion wavelength. We also complete the analysis by the accurate determination of the zero-dispersion wavelength of the fiber using the phase-matched four wave mixing process which occurs near this specific wavelength.

A universal optical all-fiber omnipolarizer

2012

International audience; Wherever the polarization properties of a light beam are of concern, polarizers and polarizing beamsplitters (PBS) are indispensable devices in linear-, nonlinear- and quantum-optical schemes. By the very nature of their operation principle, transformation of incoming unpolarized or partially polarized beams through these devices introduces large intensity variations in the fully polarized outcoming beam(s). Such intensity fluctuations are often detrimental, particularly when light is post-processed by nonlinear crystals or other polarization-sensitive optic elements. Here we demonstrate the unexpected capability of light to self-organize its own state-of-polarizatio…

Measurement of the soliton number in guiding media through continuum generation.

2020

No general approach is available yet to measure directly the ratio between chromatic dispersion and the nonlinear coefficient, and hence the soliton number for a given optical pulse, in an arbitrary guiding medium. Here we solve this problem using continuum generation. We experimentally demonstrate our method in polarization-maintaining and single-mode fibers with positive and negative chromatic dispersion. Our technique also offers new opportunities to determine the chromatic dispersion of guiding media over a broad spectral range while pumping at a fixed wavelength. (C) 2020 Optical Society of America

Simultaneous polarization attraction and Raman amplification of a light beam in optical fibers

2012

International audience; In this paper, we demonstrate that it is possible to combine both Raman amplification and polarization attraction of a signal wave in a single optical fiber by means of a counterpropagating scheme. Experiments were performed near 1550 nm in a continuous wave regime and by means of a 10 Gbit ∕ s return-to-zero signal injected in a 20 kmlong low polarization mode dispersion optical fiber. Complete repolarization and 6.7 dB amplification of the signal wave was achieved by injecting a 850 mW, 1480 nm counterpropagating polarized pump wave.