Sreekanth, K. V., Jana, S., Xinan, L., Ronghui, L., & Teng, J. (2026). Spectrally tunable singular phase at normal incidence in nanophotonic cavities. APL Engineering Physics, 1(1). https://doi.org/10.1063/5.0310658
Abstract:
The concept of singular phases at the point of darkness has been extensively studied using various optical systems, such as metamaterials and thin-film cavities, mainly for refractive index sensing. However, these systems typically work at an oblique angle of incidence. Achieving a singular phase at normal incidence is vital for practical sensing and flat-optics applications, but it remains challenging. Here, we demonstrate the singular phase at normal incidence using a grating-coupled thin-film cavity that functions at optical wavelengths. By optimizing the structural parameters of the grating and thin-film cavity, we achieve zero reflection with an abrupt phase shift at the polarization-dependent resonance of the grating. In addition, we introduce a spectrally tunable singular phase at normal incidence by integrating a phase change material (PCM) into the cavity. Using a lossless PCM, such as Sb2S3, we achieve a phase singularity with continuous spectral tunability up to 203 nm by altering its phase from amorphous to crystalline, a key feature for phase engineering in flat optics.
License type:
Attribution 4.0 International (CC BY 4.0)
Funding Info:
This research / project is supported by the A*STAR - Manufacturing, Trade, and Connectivity Programmatic
Grant Reference no. : M22L1b0110
This research / project is supported by the National Research Foundation - Competitive Research Programme
Grant Reference no. : NRF-CRP26-2021-0004
This research is supported by core funding from: National Semiconductor Translation and Innovation Centre (NSTIC)
Grant Reference no. :