Mapping local optical constants in deep-subwavelength resonant structures of ultra-high index topological insulators Bi2Se3 and Bi2Te3

Sukanta Nandi; Shany Cohen; Danveer Singh; Michal Poplinger; Pilkhaz Nanikashvili; Doron Naveh; Tomer Lewi

doi:10.1117/12.3016085

11 June 2024 Mapping local optical constants in deep-subwavelength resonant structures of ultra-high index topological insulators Bi₂Se₃ and Bi₂Te₃

Sukanta Nandi, Shany Cohen, Danveer Singh, Michal Poplinger, Pilkhaz Nanikashvili, Doron Naveh, Tomer Lewi

Author Affiliations +

Proceedings Volume PC12990, Metamaterials XIV; PC129901G (2024) https://doi.org/10.1117/12.3016085
Event: SPIE Photonics Europe, 2024, Strasbourg, France

Abstract

Optical properties of chalcogenide topological insulators (TIs), namely, Bi₂Se₃ (BS) and Bi₂Te₃ (BT) were studied across the NIR to MIR spectral ranges. In this spectral range, the experimentally measured optical constants revealed an extremely high permittivity values amounting to refractive indices as high as n≈11 and n≈6.4, for BT and BS respectively. These ultra-high index values were then utilized for demonstrating ultracompact, deep-subwavelength nanostructures (NSs), with unit cell sizes down to ~λ/10. Finally, using scattering-type Scanning Near-field Optical Microscopy (s-SNOM), local variations in the optical constants of these nanostructured TIs were studied. Nanoscale phase mapping on a BS NS revealed the role of the imaginary component of the refractive index in the observed phase shifts, varying from as low as ~0.37π to a maximum of ~2π radians across a resonance. This work thus highlights the potential of TIs as a low-loss, high index material for ultracompact nanophotonics.

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Sukanta Nandi, Shany Cohen, Danveer Singh, Michal Poplinger, Pilkhaz Nanikashvili, Doron Naveh, and Tomer Lewi "Mapping local optical constants in deep-subwavelength resonant structures of ultra-high index topological insulators Bi₂Se₃ and Bi₂Te₃", Proc. SPIE PC12990, Metamaterials XIV, PC129901G (11 June 2024); https://doi.org/10.1117/12.3016085

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