Characterisation of III–V optoelectronic devices by Internal Second-Harmonic Generation technique

A surface characterization technique based on the Internal Second-Harmonic Generation SHG.in optoelectronic devices has been used to study the mirror degradation of 1.55 mm semiconductor optical amplifiers SOAs.exposed to an antireflection coating deposition technique and 980 nm pump lasers suffering from mirror oxidation during life-tests. In both cases, an overall increase in SH emission was observed, as a consequence of mechanical stress enhancement and defects formation due to oxidation phenomena occurring at the interface between semiconductor and coating film. In the case of pump lasers, an oscillating, periodic trend superimposed to the general increasing one was also observed and interpreted as the periodic relaxation of compressive strain in the active layer due to vacancies formation in the near-mirror semiconductor layer. q1999 Elsevier Science B.V. All rights reserved.