Photoluminescent Er-doped As20Se80 thin films and channel waveguides produced by thermal reflow

Abstract

The chalcogenide glasses are an excellent material alternative for the poorly developed optics of the mid-infrared region on integrated photonics. Their great transmission in the IR region, the outstanding non-linear optical properties, and the recently explored possibility of processing by thermal reflow have sparked considerable interest in the fabrication of micro and nano-structures with symmetric and smooth surfaces suitable for optical components. The thermal reflow nevertheless is not useful for certain glass compositions since it induces phase separation and crystallization that compromise the optical quality. Rare earth-doped chalcogenides, of great interest for the development of laser and amplifiers, are especially prone to such dehomogenization since they have shown to be difficult to synthesize and process without obtaining fluorescence quenching caused by agglomeration and phase separation. In this work, we demonstrate for the first time that under certain conditions it is possible to induce thermal reflow in Er-doped chalcogenide thin films without inducing agglomeration and extinguishing the erbium emission. The films, produced by the co-evaporation of metallic erbium and As20Se80 glass matrix, demonstrated great molecular flexibility that allows to observe thermal reflow in films with erbium concentrations up to 0.6 at%. We use this thermal reflow in doped ridge channel waveguides (produced by photolithography) to reduce the optical losses and to enhance the fluorescence properties of the material by the rearrangement of the emitting ions. Our study opens the door for the fabrication and processing of rare earth-doped chalcogenide planar devices and their future integration into photonic circuits.