Apprentissage énergétique du rayonnement (rôle de l'instrument de mesure dans la validation de la modélisation)

Ce travail a pour finalité l'expérimentation d'une situation d'apprentissage du rayonnement énergétique par des élèves français (1ère S), tunisiens (2ème année), des étudiants tunisiens (1ère année). Notre problématique se développe dans des cadres historique (évolution des théories du rayonnement, de la photométrie), épistémologique (rôle de l'instrument de mesure dans la construction théorique), physique (rayonnement), psychologique (modèle du profil conceptuel), didactique (Théorie des situations). L'expérimentation a permis de vérifier les fonctions dynamiques de l'instrument de mesure, de valider partiellement notre hypothèse didactique (l'instrument de mesure est un élément du milieu qui permet la dévolution et l'apprentissage. Il est lié au symbole par la connaissance à enseigner, au dispositif et à la consigne) par l'évolution des profils conceptuels des apprenantsLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Novel design of photonic crystal dense wavelength multiplexer based on nonlinear effect

Using a two-dimensional Finite-difference time-domain method (213 FDTD), we present an extensive study of a new type of the wavelength multiplexer system. The self focusing and defocusing of the light beam are considered in this paper. The coupling between different kinds of components integrated in the same chip, in terms of coupling efficiency, is evaluated. Ultra-Dense Wavelength Division Multiplexing system (UDWDM) is of increasing demand since it provides large broad spectra that satisfy large number of users world-wide. This system can be used in the high-capacity optical fibre communication systems. The UDWDM plays a central role in optical interconnection required for highdense integrated systems, in terms of light coupling between various optical chips

Novel Multiplexer/Demultiplexer Based on Photomic Crystal Superprism

We report a novel type of dispersive structure for wavelength multiplexer/demultiplxer based on a 2D photonic crystal (PC) prism. The novel device is proposed using super dispersion of a 2D PC. Simulation is carried out to determine the angular dispersion as a function of the period. The design has been optimized to improve the performance of a system with moderate refractive index contrast. It is shown that by varying the incident angle in a wavelength range from 1.3gm to 1.5gm, a superprism effect is observed. The performance of the devices is investigated in terms of sensitivity and resolution, which would help to understand the behaviour of the superprism prior to fabrication and its integration in photonic circuits

Analysis of Wavelength Demultiplexer based on Photonic Crystals

A wavelength demultiplexer based on photonic crystal waveguide (PCW) couplers is presented. A numerical approach based on the two-dimensional finite-difference time domain is employed to analyse, design and optimise the wavelength demultiplexer based on photonic crystal Structure. The performance of the device is investigated in terms of optical efficiency, device length and losses. Significant improvement on the power efficiency and the wavelength directionality has been achieved by introducing a single defect on the crossing point between two PCWs

Realization of a High Coupling Efficiency by Employing a Concave Lens Based on Two-Dimensional Photonic Crystals with a Negative Refractive Index

A study of the interaction of a continuous-wave Gaussian beam with a concave lens used as a spot-size converter (SSC) is presented. The lens is based on a 2-D photonic crystal (PC) structure with a negative refractive index. A numerical method based on a 2-D finite-difference time domain was employed to investigate the light propagation in a photonic integrated circuitry (PIC). The PIC consisted of a single-mode fiber, an SSC, and a PC waveguide (PCW). By employing an optimized planoconcave lens, a large spot-size area of the Gaussian beam was focused/transformed into a very small spot-size area, which is even smaller than the order of the operating wavelength. Optimization of the proposed device parameters has also been reported. A significant reduction in the device size, transmission efficiency, and coupling efficiency has been achieved by optimizing the planoconcave lens and the PCW

Novel Design of Wavelength Demultiplexer based on Photonic Crystal Platform

A numerical approach based on the two-dimensional (2D) Finite Difference Time Domain (FDTD) is employed to design, analyse and optimise the wavelength demultiplexer (WDM) based on photonic crystal waveguide couplers. The performance of the WDM is investigated in terms of device length, optical efficiency and losses. Significant improvement on the power efficiency and the wavelength directionality has been achieved by introducing a single defect on the crossing point between two photonic crystal waveguide

Design of two-dimensional photonic crystal structure based in all-angle negative refractive effect for application in focusing systems

A design of a polarisation independent focusing system of electromagnetic waves in a two-dimensional photonic crystal (PC) is proposed and numerically demonstrated by using the finite-difference time-domain method. We have shown that by the careful selection of both the refractive index of the high index material and the air cylinder radius, a complete all-angle negative refraction can be obtained for both the transverse electric (TE) and the transverse magnetic (TM) polarisations. We have demonstrated that the proposed PC structures can focus either the TE or the TM or both TE and TM polarised waves with sub-wavelength resolution. In addition, a significant improvement of the image resolution has been presented

Mode Converter Optical Isolator Based on Dual Negative Refraction Photonic Crystal

A new design of an optical isolator based on photonic transitions in the interbands of a honeycomb structure that generates a dual negative refraction in a photonic crystal is presented. The involved photonic transition is associated to the perturbation of the dielectric constant of the medium. The band structure is determined using the plane wave method where the transmission spectra, field profile, and mode amplitudes are obtained by applying the finite difference time domain method. Due to the time-dependent perturbation of the refractive index of the medium that constitutes the dual negative refraction, asymmetric transmission mechanism is achieved for one of the desired modes, demonstrating optical isolation. Using the dual negative refraction effect in photonic crystal structure, the optical isolation is reported for only one of the desired optical modes. It is anticipated that the proposed mode conversion mechanism can be employed for designing ultrahigh-speed optical interconnections. The proposed optical isolator model is expected to have a significant impact on designing ultrahigh-speed integrated optical platforms