Fine-tuning of the optical properties of hollow-core light cages using dielectric nanofilms

ZIEGLER, MARIO; MAIER, STEFAN A.; JANG, BUMJOON; ANDO, RON FATOBENE; SCHMIDT, MARKUS A.; GARGIULO, JULIAN; HÜBNER, UWE

OPTICS LETTERS

OPTICAL SOC AMER

Año: 2020 vol. 45 p. 196 - 199

0146-9592

Here, we show that the optical properties of direct-laser-written on-chip hollow-core waveguides-so-called light cages-can be controlled to a very high degree by dielectric nanofilms. Using low-temperature atomic layer deposition (ALD), alumina nanofilms are concentrically deposited on the high-aspect strands that surround the central air core and confine the light via the anti-resonant effect. In accordance with modal cutoff simulations without any free parameters, a linear spectral shift of the resonances with increasing film thickness is experimentally observed. The phenomenon is explained by a shift in the dispersions of cladding supermodes. As neither cage geometry nor polymer is affected by the film deposition, our results suggest ALD to be an essential tool for fine-tuning the properties of hollow-core light cages and to protect them from aggressive substances, being relevant for, e.g., bioanalytics or quantum technology.