Application-tailored optimisation of photonic crystal waveguides

Abstract

Photonic crystal(PhC) waveguides are used for a wide range of applications with diverse performance metrics. A waveguide optimised for one application may not be suitable for others and no one-size-fits-all solution exists. Therefore each application requires a specialised waveguide design, a computationally and time intensive process. Here, we present a hybrid, multi-objective optimisation routine for PhC waveguides, to efficiently guide the device design. The algorithm can be configured to optimise for a wide range of performance metrics and applications. We demonstrate optimisations for three different applications: slow light performance, propagation loss due to fabrication disorder and delay line applications. For each optimisation target, our routine quickly finds practical waveguide designs (<48 h, on a laptop computer) that match or exceed the performance of state-of-the-art devices designed by the community over the last 10 years. This is also the first time that scattering loss from fabrication disorder has been incorporated into an optimisation algorithm, ensuring realistic predictions of a PhC waveguide design's practical performance.

Tunable Optical Buffer through an Analogue to Electromagnetically Induced Transparency in Coupled Photonic Crystal Cavities

“…It is now widely accepted that current delay lines are generally limited by the propagation loss in the structure, rather than by group velocity dispersion. [7][8][9] Significant work has gone into optimising both silicon based coupled oscillator waveguides and slow light photonic crystals, e.g. by Minkov and Savona, 10 with problems relating to backscattering understood and minimised.…”

“…Despite significant early progress on integrated delay lines based on photonic crystal waveguides and coupled cavity structures, − significant challenges remain. It is now widely accepted that current delay lines are generally limited by the propagation loss in the structure, rather than by group velocity dispersion. − Significant work has gone into optimizing both silicon based coupled oscillator waveguides and slow light photonic crystals, for example by Minkov and Savona, with problems relating to backscattering understood and minimized. Nonetheless, the high refractive index contrast of the latter (i.e., Photonic Crystals), which enables a small footprint, amplifies the effects of roughness, placing a limit on the minimum propagation loss that can be achieved, with 35 dB/ns being the current record .…”