A multimode model based on the rate equation approximation is presented in order to simulate the mode dynamics and noise characteristics of semiconductor microring lasers. The effect of straight waveguide facet residual reflectivity is studied in detail. A complete characterization is performed including calculated optical mode spectra, time traces and relative intensity noise (RIN) spectra. Different operation regimes are demonstrated, stable multimode, stable single mode, and hopping multimode dependent on the injection current and the straight waveguide reflectivity. An expansion of the stable single mode operation regime is observed up to higher injection currents with a respective suppression of the mode-hopping regime, for a power reflectivity ratio of -30dB for both facets. Moreover, the use of different reflectivities for each facet at appropriate values promotes unidirectional operation.
Microring resonators are excellent candidates for very large scale photonic integration due to their compactness, and fabrication simplicity. Moreover a wide range of all-optical signal processing functions can be realized due to the resonance effect. Possible applications include filtering, add/drop of optical beams and power switching, as well as more complex procedures including multiplexing, wavelength conversion, and logic operations. All-active ring components based in InGaAsP/InP are possible candidates for laser sources, lossless filters, wavelength converters, etc. Our work is based on measurement, characterization and proposal of possible exploitation of such devices in a variety of applications. We investigate the spectral characteristics of multi-quantum well InGaAsP(λ=1.55μm)/InP microring structures of various ring diameters and different configurations including racetracks with one or two bus waveguides and MMI couplers. The latter configuration has recently exhibited the possibility to obtain tunable active filters as well as tunable laser sources based on all-active ring-bus-coupler structures. In the case of tunable lasers single mode operation has been achieved by obtaining sufficiently high side mode suppression ratio. The tuning capability is attributed to a coupled cavities effect, resembling the case of multi-section DBR lasers. However, in contrast to the latter, the fabrication of microring resonators is considered an easier task, due to a single step growth procedure,
although further investigation must be carried out in order to achieve wide range tunability. Detailed mappings of achievable wavelengths are produced for a wide range of injection current values.
Proc. SPIE. 5452, Semiconductor Lasers and Laser Dynamics
KEYWORDS: Signal processing, Semiconductor optical amplifiers, Semiconductor lasers, Signal to noise ratio, Interference (communication), Four wave mixing, Optical amplifiers, Two wave mixing, Satellites, Nonlinear optics
A detailed numerical and experimental study of the additional RIN induced to the input waves by the FWM process, is presented. The nonlinear medium used in the experiments is a bulk Semiconductor Optical Amplifier (SOA). The measurements are carried out for different operating conditions (pumping level of the SOA, input power, input signals with different intensity noise characteristics, etc.). A complete numerical model is employed to simulate the FWM process, taking into account interaction of four waves in the SOA (two input waves and two product waves). The latter is used in order to obtain realistic behavior of the model, when operation at a wide range of input power is considered. The theoretical interpretation of the above results is based on the static transfer function of the FWM process where all waves interacting in the SOA are continuous waves (CW).