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Abstract: Single crystals of x- and z-cut were irradiated using Si-ions with energies of 550 and 750keV. The irradiation was carried out along the corresponding axial channel as well as at different tilt angles. The damage accumulation was investigated by means of Rutherford backscattering spectrometry (RBS). Due to the channeling of the ions, the damage distribution is shifted to larger depths if the irradiation is performed along low index crystallographic directions compared to that of an off-axis irradiation. Additionally, less damage is created by on-axis than by off-axis irradiation. Compared to the random irradiation with 550keV Si-ions, the etched depth increases by a factor of 1.4 and 1.2 if the irradiation is carried out along the x- and the z-axis, respectively. From the dependence of the shift of the damage peak on the tilt angle a critical angle to avoid channeling of about 1.3° was determined for 750keV Si-ions. [Copyright &y& Elsevier]

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]

Abstract: Single crystals of z- and x-cut LiNbO3 were irradiated at room temperature and 15K using He+- and Ar+-ions with energies of 40 and 350keV and ion fluences between 5×1012 and 5×1016 cm−2. The damage formation investigated with Rutherford backscattering spectrometry (RBS) channeling analysis depends on the irradiation temperature as well as the ion species. For instance, He+-irradiation of z-cut material at 300K provokes complete amorphization at 2.0dpa (displacements per target atom). In contrast, 0.4dpa is sufficient to amorphize the LiNbO3 in the case of Ar+-irradiation. Irradiation at 15K reduces the number of displacements per atom necessary for amorphization. To study the etching behavior, 400nm thick amorphous layers were generated via multiple irradiation with He+- and Ar+-ions of different energies and fluences. Etching was performed in a 3.6% hydrofluoric (HF) solution at 40°C. Although the etching rate of the perfect crystal is negligible, that of the amorphized regions amounts to 80nmmin−1. The influence of the ion species, the fluence, the irradiation temperature and subsequent thermal treatment on damage and etching of LiNbO3 are discussed. [Copyright &y& Elsevier]

Buried waveguides were produced by He+-irradiation with energies between 1 and 3 MeV and ion fluences, which are sufficient to generate multiple buried amorphous layers in KTP and Rb:KTP, respectively. Within these layers the refractive index is decreased and they act as barriers for light guiding. The irradiation causes the formation of defects within the waveguide, reducing the optical transmittance. By post-irradiation thermal annealing light scattering and absorption inside the waveguides can be significantly reduced. In the case of Rb:KTP rapid thermal annealing up to temperatures of 500 °C was found to be suitable to abolish point defects and to prevent the Rb-diffusion at the same time. Due to adjacent regions of different refractive indexes non-symmetrical electric field distributions are obtained within the waveguide. For the completely irradiated waveguides the homogeneous refractive indexes around the waveguide cause fibre-like symmetrical electric field distributions in a single-mode waveguide undisturbed of surface effects. The samples were analysed by means of various complementary methods (Rutherford backscattering spectrometry, cross-sectional transmission electron microscopy, m-line spectroscopy). The near-field pattern and the attenuation of the waveguides were measured. [Copyright &y& Elsevier]