| Wavelength-tunable semiconductor lasers are desirable light sources in wavelength-division multiplexed (WDM) fiber optic communication systems. Important parameters are tuning range, side mode suppression ratio (SMSR), linewidth, modulation bandwidth, and manufacturability.; Recently, there has been a lot of interest in microring resonators as compact filters with a high quality factor. This dissertation discusses the design considerations for passive microring resonator coupled lasers (RCLs), which utilize the microring resonators as wavelength selector inside the laser cavity. Beam propagation simulations show that a design with racetrack configuration can meet the needs of the threshold gain less than 60/cm (respectively, 80/cm) for waveguide sidewall roughness smaller than 5 nm (respectively, 10nm). The SMSR larger than 50 dB, and the linewidth in the range of 3∼500 KHz, can also be achieved. This performance is better than the current state-of-the-art distributed feedback lasers.; The design trade-offs for the double ring resonator coupled lasers are investigated. With two rings with slightly different radii, one can extend the tuning range greatly with the use of the Vernier effect. High-power limitation of the RCL is analyzed with bi-directional coupled propagation equations including the material nonlinearity. It is shown that the two-photon absorption, due to resonance-enhanced light intensity in the microring, is the main limiting factor. Experimental demonstration of RCL is achieved with InP ridge-waveguide microring filters and an external Er-doped fiber amplifier as the gain medium. Monolithic structures are also characterized. It is shown that coupling loss between active and passive waveguides in excess of -3 dB is the main limitation for room temperature lasing operation.; When semiconductor lasers are integrated with optical amplifiers and electroabsorption modulators, thermal management and crosstalk are important issues that limit the performance of monolithically integrated devices. By using a thermoreflectance imaging technique thermal-run-away phenomenon at the input of electroabsorption modulator is revealed. A self-consistent finite difference opto-thermo-electrical modeling is developed, predicting well the observed chip surface temperature and the thermal-run-away. With improved thermal management of the electroabsorption modulator, a high power dissipation limit of more than 300 mW is achieved. Simulation of the large thermal crosstalk between the active and passive regions in the integrated circuits indicates that the wavelength calibration for every power level should be performed. |
