Christine Restoin

Electron-Beam Poling on Ti:LiNbO(3).

The periodic domain inversion by direct electron-beam (EB) bombardment on Ti:LiNbO(3) is presented. Gratings with a 6.6-mum period are achieved. The inverted patterns are observed after chemical etching by use of a scanning electron microscope, and they exhibit a high resolution, as expected. Next, the influence of the EB parameters on the inversion phenomenon is developed for both LiNbO(3) and Ti:LiNbO(3). In this way we can provide an explanation of the phenomenon of domain inversion with an EB, which is not completely understood. Finally, quasi-phase-matched second-harmonic generation is presented in bulk LiNbO(3) by use of a Nd:YAG laser light. These experiments allowed us to achieve the characteristics of the inverted domains along the crystal in particular.

Nanostructured optical fiber obtained by the sol-gel process in the SiO 2 -ZrO 2 system doped with erbium ions

We present experimental results concerning the first silica-zirconia nanostructured optical fiber doped with erbium ions obtained by the sol-gel process. The microstructure and the optical properties of the fiber are characterized.

Fabrication of PBG structures by electron beam bombardment on LiNbO/sub 3/

Summary form only given. Photonic band gap (PBG) structures consist in gratings which have a periodic and high index modulation contrast. Their interest is now well known to make filters, waveguides, micro-resonators, superprisms, etc. This paper is devoted to the achievement of PBG structures in LiNbO/sub 3/, well known for its interesting linear and nonlinear optical properties. As the lithium niobate is a ferroelectric crystal, its spontaneous polarisation can be reversed. Among the different methods already developed for ferroelectric domain inversion, electron beam (EB) bombardment is one of the sole technique able to operate at a submicrometer scale. EB irradiation has been performed by a scanning electron microscope which permitted to scan the beam or to move it from point to point.

Periodically poled lithium niobate by electron beam: irradiation conditions and second harmonic generation

Second Harmonic Generation (SHG) using counter-propagating Quasi Phase Matching (QPM) configuration often requires a fine non-linearity with a period of a fraction of a micrometer. The direct Electron Beam (EB) domain reversal technique seems to be promising to achieve gratings on LiNbO3 with such a small period compared to other current poling technologies as it is lithographic free and exhibits a very high theoretical resolution (5 mm). We present here, a preliminary study concerning the influence of EB irradiation conditions on domain inversion; SHG is also examined on a 6.58 j.tm inverted periodic domain grating in lithium niobate using a Nd-YaG laser light. It is well known that LiNbO3 is an attractive material for many optical applications because of its transparency over a large wavelength band (350 mm to 5000 mm) and its high nonlinear coefficients. EB irradiation is performed using a Scanning Electron Microscope (SEM) driven by a Computer Aided Design (CAD) application developed in our laboratory. Various structures such as periodic gratings can be written with the chosen period. The ferroelectric domain inversion is investigated as a function of the accelerating voltage of the electrons (10 to 30 kV), the scanning speed of the EB (0.97 to 7.76 mm/s) and the current received by the sample (1.6 to 14 nA). The inversion patterns have been revealed by chemical etching (HF) and they have been observed using SEM. It has been shown that the duty cycle is respected on the irradiated face. The SHG conversion efficiency is measured as a function of the temperature and the grating period is calculated (value of6.564 jim).