Waveguide barriers with adjustable refractive index produced in KTP by irradiation with He- and Li-ions

Abstract: Z-cut KTP single crystals were irradiated with 300keV He- and 1MeV Li-ions at fluences between 1×1015 and 2×1016 cm−2. The irradiation decreases the refractive index in the depth region of high nuclear energy deposition and, as a consequence, a waveguide barrier is formed. The damage accumulation was monitored using Rutherford backscattering spectrometry (RBS). The characterization of the waveguide was carried out by optical transmission and m-line spectroscopy. The difference of the refractive index between the waveguide and the barrier increases with increasing ion fluence. The maximum difference is reached at a fluence, which is noticeable higher than the amorphization fluence measured by RBS. The number of displacements per atom, which are necessary to obtain identical reductions of the barrier refractive index is higher for lower ion masses. The results show that the refractive index can be purposefully adjusted by varying the ion mass and the ion fluence. [Copyright &y& Elsevier]