Recent content by Barth

Thanks a lot

The source we are using is the "classic" Tsunami-Opal femtosecond line. We then have at 1500nm a relatively high peak intensity, that's why i would like to evaluate two-photon absorptions.

How does work the two-photon absorption ? Does it exist a Beer-Lambert law for this kind of process? If yes, does someone know where i could find the order of magnitude of two-photons absorption coefficient for silicon at 1500 nm ? Barth

Yes, it exists. There is two types of effects that change the refractive index of a material under a electric field: Pockels effet and Kerr effect. Pockels effect is linked with second-order nonlinear effects, so the materials that can show this effect are non-centrosymmetric nonlinear...

You can not really "change the gap" by doping a cristal. When you dope the cristal, you introduce impurities in the lattice. These impurities creates localised states for the electrons, whose energy is inside the gap. So you don't change the gap, you only create disrete levels inside. All...

To have a Raman anti-stoke diffusion, we need to have a transition of an atom initially in a excited vibrationnal level to the ground level (if we forget the intermediate virtual state). The stoke diffusion, instead, relies on a transition from the ground level to an excited vibrationnal level...

So if i understood well, in a quantum dot, there is two type of states: the discrete "particule in a box", one electron states, equivalents in the confined object of the (kx,ky,kz,n) states of the bulk, and excitonic states, equivalents of the excitonics states of the bulk. And the only...

Why do we talk about " quantum dot excitons" ? For me, excitons and quantum dots are two distincts objects For me, excitons (at least in a bulk) are a bound state of an electron and a hole, bound by the attractive coulomb potential, and their binding energy and wavefunctions are the one of a...