AUTHORS:

Pruszyńska-Karbownik E., Fąs T., Brańko K., Yavorskiy D., Stonio B., Bożek R., Karbownik P., Wróbel J., Czyszanowski T., Stefaniuk T., Pacuski W., Suffczyński J.

ABSTRACT:

High refractive index (4.4 at 1100 nm), negligibly small absorption in the near-infrared spectral range, and ease of processing make MoSe₂ the perfect material for applications in near-infrared photonics. So far, implementation of MoSe₂-based photonic structures has been hindered by the lack of large-surface MoSe₂ substrates. The use of molecular beam epitaxy allows the production of homogeneous layers of MoSe₂ with a few-inch surface and a thickness controlled at the sub-nm level. In the present work, we design by theoretical calculations and fabricate by a simple lithography process an ultrathin subwavelength grating out of a 42 nm thick, epitaxially grown MoSe₂ layer. Our polarization-resolved reflectivity measurements confirm that the gratings host a peculiar type of a confined optical mode that is a bound state in the continuum. Moreover, the fabricated structures enhance the efficiency of the third-harmonic generation by over 3 orders of magnitude as compared to the unstructured MoSe₂ layer. The presented results are promising for the realization of flat, ultracompact devices for lasing, wavefront control, and higher-order topological states of the light.

ACS Nano, 2026, vol. 20(9), pp. 7426-2437, doi: 10.1021/acsnano.5c12870