Study of the absorption coefficient in layers of a semiconductor laser heterostructure

A method of studying the absorption coefficient in layers of semiconductor lasers is proposed. Using lasers based on MOVPE-grown separate-confinement heterostructures with a broadened waveguide, the absorption coefficient is investigated under pulsed current pumping. It is found that when the pump current flows through the laser in question, an additional internal optical absorption arises in the heterostructure layers. It is shown that an increase in the pump current density up to 20 kA cm^-2 leads to an increase in absorption up to 2.5 cm^-1. The feasibility of studying free-carrier absorption in the active region is demonstrated.