Realization and infrared to green upconversion luminescence in Er:YALO3 ion-implanted optical waveguides

Ion implantation in optical materials is increasingly used in fabrication of optical waveguides of micrometric dimensions. Implantation has been proved to form planar and channel waveguides in YAG single crystals [1, 2]. Planar waveguides are obtained by homogeneous irradiation of the crystal surface with He or H ions at a given energy (in the MeV range), while mask technique has to be used to form channel waveguides. Depending of the nature of the crystal, either negative or positive index change is induced by the energy deposition process, at the end of ion track or all along the trajectory, respectively. We have developed a new route for index structuring a crystal surface, i.e. to fabricate channel waveguides, by using a specific slit-based set up and multiple implantations [2]. Er:YAlO3 is known as a quite efficient infrared to green upconversion system [3, 4]. In the goal of forming miniature upconversion lasers for integrated optics, we used the light ion implantation technique to elaborate planar and channel waveguides in 1 at.% Er doped YAlO3 single crystals and we studied the guided green luminescence observed under infrared laser excitation. Several waveguides of different dimensions, using different doses of He or H ions per cm, were made. To our best knowledge, it’s the first observation of ion-implanted waveguides in this material. Each waveguide was excited by sapphire-titanium laser in the 740 to 840 nm wavelength range. The upconversion mechanism responsible to the green luminescence around 550 nm is a combination of cross relaxation energy transfer and nonresonant sequential two-photon absorption and the emission lines have the same spectral position as in the bulk material. In the channel proton-implanted waveguides of 8 × 15 μm dimension, performed by positive index change, the intensity of this upconverted luminescence increases with the light ion dose used for their fabrication.