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arXiv · 2502.03121

Optical bound states in the continuum in subwavelength gratings made of an epitaxial van der Waals material

Emilia Pruszyńska-Karbownik·Tomasz Fąs·Katarzyna Brańko·Dmitriy Yavorskiy·Bartłomiej Stonio·Rafał Bożek·Piotr Karbownik·Jerzy Wróbel·Tomasz Czyszanowski·Tomasz Stefaniuk·Wojciech Pacuski·Jan Suffczyński
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Abstract

High refractive index (4.4 at 1100 nm), negligibly small absorption in near-infrared spectral range, and ease of processing make MoSe$_2$ a perfect material for applications in near-infrared photonics. So far, implementation of MoSe$_2$-based photonic structures has been hindered by the lack of large surface MoSe$_2$ substrates. The use of molecular beam epitaxy allows the production of homogeneous layers of MoSe$_2$ 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 42-nm thick, epitaxially-grown MoSe$_2$ 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 three orders of magnitude as compared to the unstructured MoSe$_2$ layer. The presented results are promising for the realization of flat, ultra-compact devices for lasing, wavefront control, and higher-order topological states of the light.

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Emilia Pruszyńska-Karbownik, Tomasz Fąs, Katarzyna Brańko, Dmitriy Yavorskiy, Bartłomiej Stonio, Rafał Bożek, Piotr Karbownik, Jerzy Wróbel, Tomasz Czyszanowski, Tomasz Stefaniuk, Wojciech Pacuski, Jan Suffczyński. 2025-02-05. Optical bound states in the continuum in subwavelength gratings made of an epitaxial van der Waals material. https://doi.org/10.1021/acsnano.5c12870

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