Femtosecond-laser fabrication of magneto-optical waveguides in terbium doped CaLiBO glass

Abstract

Femtosecond laser micromachining has potential application in integrated photonics thanks to its ability to produce micrometer-size three-dimensional structures in different types of materials, including the ones whose properties can be externally altered, which allows for the fabrication of optically active devices. In this work, we demonstrate the fs-laser fabrication of magneto-optical waveguides in CaLiBO (calcium-lithium tetraborate) glasses codoped with Yb+3 and Tb3+ ions. Single-mode type waveguides were produced using fs-pulses with ∼0.1 J/cm2 and 6.5 × 105 pulses/spot, an important feature for integrated photonic devices. The fabricated waveguides display Faraday effect, with a Verdet constant of 560° T−1m−1, for the sample containing 2% of Tb3+, which is equivalent to the one observed for the bulk. Such a result demonstrates that fs-laser micromachining, in the conditions used here, does not negatively affect the magneto-optical properties of the sample. Thus, our results open a new pathway towards the processing of magneto-optical waveguides aimed at applications in magneto-optical photonic microdevices.