Single-mode Bragg ring laser diodes

We have designed and fabricated a monolithic semiconductor ring laser based on a Bragg waveguide structure. Through careful control of the waveguiding, we have overcome the inherent "leaky" nature of this waveguide mode and demonstrated a ring laser lasing in the Bragg mode. Best behavior was obtained from lasers with a diameter of 400 μm, where they exhibited output power >1 mW, in continuous wave (CW) operation. A tangent waveguide provided access to the ring cavity using two ports through evanescent coupling. To meet the stringent waveguiding requirements imposed by the Bragg structure, a two-step etching process, consisting of a shallow-etched coupler and a deep-etched bend section of the ring, was developed in order to reduce the bend and scattering losses. The laser showed a threshold current density of ∼2.2 kA=cm2 inCWoperation with single longitudinal mode operation with a signalto- noise ratio of 30 dBm obtained at 1.5 Ith. Broadband phase-matching of χ. (2) nonlinearity is observed, offering self-pumped parametric C-band conversion >40 nm with efficiency of 142%W-1 cm-2.