C. Grezes-Besset

Comparison of surface and bulk scattering in optical multilayers

Electromagnetic theories provide a tool to detect the origin of scattering in optical multilayers. Illumination and observation conditions that cause surface and bulk scatterings to have different behaviors are pointed out. Angular, wavelength, and polarization dependences are investigated for the location of structural irregularities at interfaces or in the bulk of a multilayer. Specific experiments can be designed.

Nd:MgO:LiNbO 3 waveguide laser and amplifier

We report efficient operation of a channel waveguide laser and a channel waveguide amplifier in Nd:MgO:LiNbO(3). For the laser a cw output power of 2.9 mW was obtained for 23.6 mW of absorbed pump power. The absorbed pump power at threshold was 1.5 mW, and a slope efficiency of 13% was achieved. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power.

Description of a scattering apparatus: application to the problems of characterization of opaque surfaces

We show how the complexity of a micropolished optical surface can be investigated in detail by measurement of the distribution of scattered light. We deal with problems of roughness anisotropy and uniformity together with cleaning problems. Experimental results concern numerous black glasses from different polishing shops and allow a determination of the polish inhomogeneity in a same glass set. After that, we present a detailed study of the apparatus function of the scatterometer, and we determine the limits of validity of our optical characterization method.

Self-frequency-doubled high Δn proton exchange Nd:LiNbO3 waveguide laser

Abstract We report the realization of the first self-frequency-doubled waveguide laser. The structure is based on a high Δ n proton exchange waveguide in z -cut Nd:MgO:LiNbO 3 which leads to new lasing wavelengths in the material. Two types of self-doubled harmonic radiation have been observed: guided semi-leaky waves and Cerenkov waves. Cerenkov type sum frequency generation, due to an interaction between the pump and laser frequencies, has also been observed. Parametric conversion efficiencies with the configuration described are limited to low values, essentially because of mode conversion effects due to constraints introduced by the high Δ n proton exchange.

Étude de la diaphonie d’un système de démultiplexage par filtres interférentiels

RésuméDans le cadre d’un projet développé en collaboration avec le Centre national d’études spatiales (cnes), les auteurs ont réalisé la maquette d’un séparateur spectral pour les télécommunications entre satellites. On décrit rapidement le principe du système. Les mesures de diaphonie sur les différentes voies du démultiplexeur ne concordent pas bien avec les performances théoriques que l’on pourrait en attendre. Au degré de précision qui est nécessaire, on ne peut pas négliger la lumière parasite qui provient de la diffusion par les irrégularités des surfaces et interfaces des différents filtres mis en jeu dans chacune des voies du démultiplexeur. Compte tenu des conditions d’éclairement de chacun des éléments de l’éclateur spectral, on peut théoriquement mettre en évidence les points les plus critiques du système du point de vue de la diffusion et chercher à la diminuer autant que possible pour réduire la diaphonie.AbstractThrough a collaboration with the Centre national d’études spatiales (cnes), we have realized a spectral separator model for telecommunication between satellites. We describe the principle of the system. Measurements of cross-talk on the different tracks of the spectral separator are sometimes far from previsions. We know that it is necessary to take account of the light scattered from surface irregularities and filter interfaces. Taking account of the illumination conditions of each component of the spectral separator, it is theoretically possible to display the most critical elements from a scattering point of vue and to try to reduce these losses as much as possible to minimize cross-talk.

LiNbO3 with rare earths: lasers and amplifiers

Nd:MgO:LiNbO3 combines the laser capabilities of rare-earth doped crystals and the non- linear and electro-optic properties of a well-known material in integrated optics. In this paper the basic characteristics of such a material are reviewed with respect to the goal of fabricating integrated optic lasers and amplifiers.