Fabrication and characterization of GaInNAs/GaAs semiconductor optical amplifiers

The constraints on dilute-nitride Semiconductor Optical Amplifiers (SOAs) for multi-wavelength amplification have been evaluated. SOAs have been fabricated by angling the facets of a GaInNAs/GaAs edge emitting laser using gas enhanced focused ion beam etching. The original laser has been characterized in terms of its temperature dependence and net modal gain. A full width half maximum (FWHM) of 40nm has been found at 298K. Good temperature stability has also been found with a value of 0.35nm/K for the lasing wavelength. The good temperature stability of the device has been explained in terms of the role that the monomolecular recombination plays in the temperature dependence of the device. The monomolecular recombination has been reported temperature independent having two key effects; reduction of the temperature performance and reduction of the dynamic performance in terms of an increase in the threshold current and a decrease of the high speed potential. Iodine gas enhanced focused ion beam etching (GAE-FIB) has been used for the fabrication of the SOA, the iodine gas increasing the etching rate by a factor of 2.5. The fabrication has been completed in two steps; in the first one the facets have been angled and in the second step a cross-section procedure has been employed for smoothing of the facets. Once the SOA has been fabricated its potential for simultaneous multiple channel amplification has been studied. A flat gain spectrum over a range of 40nm has been obtained. This value and the wavelength range have good agreement with the net modal gain measured in the original laser device. In addition, minimum channel interspacing has been achieved with no wavelength degradation.