Seminarium Fizyki Ciała Stałego

Transition metal dichalcogenides (TMDs) offer interesting possibilities in nanophotonics due to their remarkable optical and excitonic properties. Leveraging a large anisotropic refractive index of dielectric/semiconducting TMDs, it becomes possible to utilize them as a novel material platform to confine and guide light at the nanoscale. These advances are enabled by advanced nanofabrication tools capable of creating diverse geometries with ultrasharp, sub-single nanometer precision. These tools have to be combined with accurate knowledge of dielectric constants, which we provide for a number of TMDs, in order to design nano-optical devices, such as single particle resonators, photonic crystals, waveguides, arrays of nanoparticles as well as their inverse designs. Here, as the first example we discuss the design and fabrication of efficient nonlinear TMD nanodisks based on MoS2, which provide close to four orders of magnitude enhancement of second harmonic generation. In the second example we optimize and fabricate high-quality nanohole-based metasurfaces in an MoS2 nanofilm. Depending on the nanohole shape, the metasurfaces can be tailored to support broken in-plane symmetry, allowing for realization of quasi-bound-states-in-the-continuum. In both cases, the optimization of the nonlinear signal is supported by first principles calculations of the second order polarizability tensor.