Wavelength stabilized single-mode lasers by coupled micro-square resonators

Wavelength stabilized single-mode lasers were realized by on-chip coupling of a ridge waveguide laser with two micro-ring resonators. The micro-ring resonators were fabricated by deeply etching to achieve high lateral optical confinement and to allow small ring diameters in the range between 20-60 (mu)m. A square-like ring geometry with 45(degree)/ facets was used to improve design control and side-wall quality. By using micro rings with two different diameters of 50 and 60 (mu)m, a free spectral range of about 18 nm could be obtained which allow a stable single-mode operation with a side-mode suppression ratio of more than 40 dB and a continuous-wave output power of 30 mW per facet at room temperature.