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

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.

References in corpus (10)

• Topological nature of bound states in the radiation continuum
• High-Q Resonances Governed by the Quasi-Bound States in the Continuum in All-Dielectric Metasurfaces
• Strongly enhanced light-matter coupling of a monolayer WS2 from a bound state in the continuum
• Generation of even and odd high harmonics in resonant metasurfaces using single and multiple ultra-intense laser pulses
• Strong coupling between excitons and quasi-Bound states in the continuum in the bulk transition metal dichalcogenides
• Refractive uses of layered and two-dimensional materials for integrated photonics
• Temperature-dependent excitonic light manipulation with atomically-thin optical elements
• Realization of Z${}_2$ topological photonic insulators made from multilayer transition metal dichalcogenides
• Optical, electronic and structural properties of ScAlMgO4
• Concept of Inverted Refractive-Index-Contrast Grating Mirror and Exemplary Fabrication by 3D Microprinting