Concepedia

Subwavelength grating periodic structures in silicon-on-insulator: a new type of microphotonic waveguide

Przemek J. Bock, Pavel Cheben, Jens H. Schmid, J. Lapointe, A. Delâge, Siegfried Janz, G. C. Aers, Dan‐Xia Xu, A. Densmore, Trevor J. Hall

Optics Express · 2010 · 305 citations · 35 references

DOI Full text

Open access

TL;DR

Unlike other periodic waveguides such as line‑defects in a 2D photonic crystal lattice, a subwavelength grating waveguide confines light as a conventional index‑guided structure and does not exhibit optically resonant behaviour. The study reports the experimental demonstration and analysis of a new waveguide principle using subwavelength gratings. They are fabricated with a single etch step in silicon‑on‑insulator, enabling flexible control of the core’s effective refractive index through lithographic patterning. Measurements show propagation loss as low as 2.1 dB/cm with negligible polarization and wavelength dependence, and a nearly constant group index of ~1.5 across the telecom C‑band, outperforming conventional silicon waveguides.

Abstract

We report on the experimental demonstration and analysis of a new waveguide principle using subwavelength gratings. Unlike other periodic waveguides such as line-defects in a 2D photonic crystal lattice, a subwavelength grating waveguide confines the light as a conventional index-guided structure and does not exhibit optically resonant behaviour. Subwavelength grating waveguides in silicon-on-insulator are fabricated with a single etch step and allow for flexible control of the effective refractive index of the waveguide core simply by lithographic patterning. Experimental measurements indicate a propagation loss as low as 2.1 dB/cm for subwavelength grating waveguides with negligible polarization and wavelength dependent loss, which compares favourably to conventional microphotonic silicon waveguides. The measured group index is nearly constant n(g) ~1.5 over a wavelength range exceeding the telecom C-band.