Two-bandgap semiconductor optical amplifier integrated using quantum well intermixing

We propose and fabricate a two-bandgap SOA device integrated monolithically using a quantum well intermixing technique on an AlInGaAs-based multiple quantum well structure. With increased current injection into the wide bandgap section, the gain peak wavelength shows a shift to the blue and the gain at shorter wavelengths is significantly enhanced. The 3-dB gain bandwidth is extended with this two-bandgap SOA device, demonstrating the potential for realisation of wide bandwidth SOAs. Moreover, it is found that saturation output power depends on the direction of propagation, which may arise from a lower differential gain and/or a shorter carrier lifetime in the wide bandgap section.