Semiconductor optical amplifiers: multifunctional possibilities, photoresponse and phase shift properties

Laser amplifiers based on semiconductor diodes are discussed with respect to their multifunctional possibilities including signal and power amplification, switching, phaseshift, photodetection and non-linear properties. The analysis is given of the electrical response (so called 'optoelectronic signal') to a passing optical signal. Experimental data are obtained on photoresponse, inversion threshold and phaseshift measurements in InGaAsP/InP SOA diodes. The optoelectronic response changes sign at an inversion threshold ('transparency current') thus the latter can easily be measured in lasers and amplifiers. This allows electrical diagnostics of the operation mode. An amplifier-photoreceiver may be a suitable device for optoelectronics.