Monolithically Integrated Tunable Laser Using Double-Ring Resonators With a Tilted Multimode Interference Coupler

A monolithically integrated tunable semiconductor ring laser consisting of a semiconductor optical amplifier and two ring resonators with tilted multimode interference (MMI) couplers is presented. The characteristic response of the ring resonators is discussed for various cross coupling strengths by adjusting the angle of the tilted MMI couplers. The ring laser has a wavelength tuning range of 11 nm and a sidemode suppression ratio larger than 40 dB for a cross coupling strength of 0.09. The peak power of the laser is larger than -3 dBm for chip-to-fiber coupling.