Compact trench-based silicon-on-insulator rib waveguide ring resonator with large free spectral range

We demonstrate a compact trench-based silicon-on-insulator (SOI) rib waveguide ring resonator comprised of trench-based bends and splitters. It has a perimeter of 50 μm and occupies an area of only 25×25 μm. The measured free spectral range (FSR) is 13.2 nm, which the largest reported for an SOI rib waveguide ring resonator. The measured FSR, full width at half maximum, and quality factor match reasonably well with analytical calculations. Further calculation shows that a FSR of 50.8 nm is achievable for an SOI rib waveguide ring resonator with a perimeter of 15 μm.