Fig. 1: The concentric racetrack resonator design.
From: Broadband high-Q multimode silicon concentric racetrack resonators for widely tunable Raman lasers
a Structure of the concentric racetrack resonator with a p-i-n junction to remove the free carriers. Schematic from the top view with geometric parameters. w0: 0.88 µm; win: 3 µm; wout: 1.5 µm; gap1: 0.4 µm; gap2: 0.4 µm; Rout: 200 µm; Ls: 690 µm. b Simulated coupling Q factors versus wavelengths from 1200 to 1700 nm. c Simulated mode propagates mainly in the outer racetrack, and modes are excited in the inner racetrack. The color bar indicates the intensity of the electric field |E|. d Calculated optical path lengths at the fundamental transverse electric (TE0) modes of the outer and the inner racetracks. e Simulated transmission spectra around 1329.5 nm with different coupling coefficients ut between the inner and outer racetracks. f Simulated transmission spectrum of the multimode concentric resonator from 1480 to 1481.5 nm.
