We report on the first observation of topologically stable spatially localized multivortex solitons generated in optically induced hexagonal photonic lattices. We demonstrate that topological stabilization of such nonlinear localized states can be achieved through self-trapping of truncated two-dimensional Bloch waves and confirm our experimental results by numerical simulations of the beam propagation in weakly deformed lattice potentials in anisotropic photorefractive media.

We report on the experimental observation of stable double-charge discrete vortex solitons generated in hexagonal photonic lattices created optically in self-focusing nonlinear media and show that single-charge vortex solitons are unstable in analogous conditions. Subsequently, we study, both theoretically and experimentally, the existence and stability of spatial vortex solitons in two-dimensional hexagonal photonic lattices. We demonstrate that the stability of the double-charge vortices is a consequence of the intersite power exchange in the vortex soliton, and we provide a simple stability criterion on the basis of the analysis of the corresponding discrete nonlinear model. We extend our analysis to the case of defocusing nonlinearity and show the inversion of the vortex stability properties resulting in the fact that single-charge vortices become stable while their double-charge counterparts are unstable.

The performance of EUV resists is a key factor for the cost-effective introduction of EUV lithography. Although most of the global effort concentrates on resist performance at 22 nm half-pitch, it is crucial for the future of EUVL to show its extendibility towards further technology nodes. In the last years, the EUV interference lithography tool at Paul Scherrer Institute, with its high-resolution and well-defined areal image, has been successfully employed for resist performance testing. In this paper, we present performance (dose, CD, LER) of a chemically-amplified resist for a range of 16 nm to 30 nm HP. Cross-sectional SEM images of the patterns are presented providing valuable insight into the resist's performance and failure mode. The reproducibility of our experiments are presented by repeating the same exposures with constant process conditions over the course of several months, demonstrating the excellent stability of the tool as well as the long shelf-life of our baseline resist. In addition, a comparative study of performance (dose, CD, LER) of different inorganic resists is provided. Patterns of 16 nm and 10 nm HPs are demonstrated with an EUV CAR and inorganic resists, respectively. Moreover, initial results of patterning with 6.5 nm wavelength are presented.