Coupled photonic crystal nanobeam cavities

TL;DR

This paper presents the design, fabrication, and experimental analysis of coupled silicon nanobeam photonic crystal cavities, demonstrating high Q factors and tunable modes with potential applications in integrated photonics.

Contribution

It introduces a novel approach to coupling nanobeam cavities and provides experimental validation of high Q factors and tunable mode properties.

Findings

Coupled modes exhibit a differential wavelength shift of 70 nm.

Q factors exceeding 200,000 were experimentally achieved.

Mode coupling and wavelength tuning are demonstrated for both on-substrate and free-standing nanobeams.

Abstract

We describe the design, fabrication, and spectroscopy of coupled, high Quality (Q) factor silicon nanobeam photonic crystal cavities. We show that the single nanobeam cavity modes are coupled into even and odd superposition modes, and we simulate the frequency and Q factor as a function of nanobeam spacing, demonstrating that a differential wavelength shift of 70 nm between the two modes is possible while maintaining Q factors greater than 10^6. For both on-substrate and free-standing nanobeams, we experimentally monitor the response of the even mode as the gap is varied, and measure Q factors as high as 200,000.