The fabrication of on-chip optical isolators to protect integrated optical sources is one of the major challenges of research in integrated optics. Their operation principle is based on the control of the guided-wave polarization and the most common structures are composed of a polarization splitter, a non-reciprocal rotator based on the Faraday effect, and a reciprocal rotator. The reciprocal rotator is a device that rotates the wave polarization by 45°. This can be achieved by creating a relative phase shift between the waveguide’s two polarization eigen states or by twisting its optics axis thanks to an appropriate shaping of its core. In this work, we propose the design and simulation of a waveguide with optics axes tilted by 45° fabricated by two cascaded field-assisted ion exchanges on a glass substrate and an encapsulation. The dependences of the proposed design on process time, temperature, applied voltage and photolithography over-etching are investigated. The final device exhibits a 45.1° rotation of its optical axes and less than 5% variation on the C+L telecommunication band.
This paper deals with an experimental non-destructive technique for the measurement of polarization behavior of integrated optical waveguides. It is based on a high resolution polarimeter associated to an ellipsometric-type calibration which allows determining the full state of polarization of the output light. A magneto-optic perturbation is also added to generate TE/TM mode beating, whose spatial period is directly linked to the modal TE/TM birefringence. This equipment is first qualified by the measurement of modal birefringence in totally or partially buried ion exchanged waveguides. The results show that the value of the birefringence varies as a function of the diffusion aperture width or with the burying depth. By adding a magneto-optical cover layer, consisting in magnetic nanoparticles doped silica matrix obtained by a sol gel process <sup>1</sup>, we evidence a huge increase of the beating magnitude and a decrease of the modal birefringence.