Optical characterization of active waveguides produced in lithium fluoride by He+ implantation

Planar active waveguides, produced in lithium fluoride crystals by implantation with 2 MeV He⁺ ions at several doses, have been characterized by optical absorption, photoluminescence and m-lines spectroscopy. All the colored samples support several modes, whose analysis allows reconstruction of the depth refractive index profiles of the waveguides as a function of dose. Two competitive physical mechanisms, associated with different processes of energy deposition along the ion track, are responsible for positive and negative modifications of the refractive index in the irradiated volume.