Seminarium Fizyki Ciała Stałego

The field of sub-wavelength optics investigates the interactions between light and objects that are smaller in size than the wavelength of light. A canonical example is a subwavelength grating, which is made of dielectric slabs spaced periodically to produce a one-dimensional structure. The subwavelength grating, capable of functioning as a compact mirror or a high quality factor nanocavity, presents an appealing alternative to the commonly employed multilayer and bulky photonic structures based on Distributed Bragg Reflectors.[1] In my talk, I will focus on subwavelength gratings in two limiting cases of the refractive index of the material that the grating is made of. In the first part of my talk, I will show design, fabrication, and optical properties (including observation of bound states in the continuum and third harmonic generation) in subwavelength gratings made out of a tens-of-nm thick MBE-grown MoSe2 layer (refractive index as high as 4.5 at 1100 nm) [2]. In the second part of my talk, I will demonstrate subwavelength gratings produced by 3D microprinting of a low refractive index (1.53) IP-Dip photoresist on high refractive index cladding layer (inverted refractive-index-contrast grating).[3] The presented flexibility of the design is promising for application of subwavelength gratings in scalable, high-performance, integrated photonics. [1] M. Marciniak et al., Impact of stripe shape on the reflectivity of monolithic high contrast gratings, ACS Photonics 8, 3173 (2021). [2] E. Pruszyńska-Karbownik et al., Optical bound states in the continuum in subwavelength gratings made of an epitaxial van der Waals material, arXiv:2502.03121 (2025). [3] E. Pruszyńska-Karbownik et al., Concept of Inverted Refractive-Index-Contrast Grating Mirror and Exemplary Fabrication by 3D Microprinting, Nanophotonics 12, 3579 (2023).