Rare earth-doped confined structures for amplifiers and lasers

Here, we present an overview of the specific spectroscopic properties of fl uoride planar waveguides which emphasize the difference between rare earth- doped waveguide and bulk and demonstrate their potentiality to be used as l asers and amplifiers. We illustrate this with recent results obtained at st rategic wavelengths for telecommunications. Furthermore, we are dealing wit h even more confined structures such as optical microcavities that are reso nators in which at least one of the dimensions is of the order of the optic al wavelength. These structures enable to control the spontaneous emission properties of rare-earth doped materials placed inside them. (C) 2000 Elsev ier Science S.A. All rights reserved.