PhD Defense of JORDAN Elodie

The fabrication of the first laser in 1960 and the growth of fiber optics telecommunications have led to the development of integrated optics circuits. Theses lasts are efficient solutions to compacity and misalignment issues. Moreover, polarization management in integrated circuits enables to increase the data rate, to guaranty the signals reliability or to protect optical sources. The work presented here is dedicated to this last application, which is the motive of a long-term collaboration between IMEP-LAHC and the Hubert Curien institute in Saint-Etienne. Indeed, we proposed to fabricate a 45° reciprocal polarization rotator that is part of the optical isolator’s design, along with a polarization splitter and a Faraday rotator. We choose to use a field-assisted ion-exchange technique (FAIE). The implementation of the polarization rotator requires managing the side effects of the electrical field lines occurring during a FAIE. It allows controlling the waveguide core’s shape and thus the eigen axes tilt. It was obtained thanks to two cascaded FAIE. The first one, an Ag+/Na+ ion exchange, creates a high refractive index waveguide while the second one, a Na+/Na+ ion exchange, modifies the shape of the waveguide’s core. Measurements of the experimental polarization behavior are a first proof of a controlled tilt of eigen axes in this technology. Indeed, the waveguide exhibits a tilt of its eigen axes of (46.6 ± 0.1)° at the input and (42.3 ± 0.1)° at the output. The numerical study of the reciprocal rotator’s process has also been proposed and the adiabaticity of the design analytically validated. The first realization highlights high propagation losses that can be linked to the degassing of the nitrate salts occurring during the FAIE. Possible improvements are thus suggested in the document. An enhancement of the Faraday rotator’s design is also proposed. It is obtained thanks to the fabrication of a waveguide exhibiting a negative birefringence whose design exploits the progress achieved on the FAIE. A complete fabrication process of the integrated isolator, taking into account the thermal budget, is also proposed , as well as a TE/TM mode evolution converter.
Finally, a first study of a Tl+/Na+ ion exchange, opening the polarization’s control to the visible spectral range is proposed.

Key words :
Glass integrated optic, field-assisted ion-exhange, polarization rotator, guided polarization, eigen axes tilted

Members of jury :