Fabrication of saturable absorbers in InGaAsP-InP bulk semiconductor laser diodes by heavy ion implantation

Several semiconductor Fabry-Perot laser diodes with InGaAsP-InP bulk active layers have been implanted with oxygen and phosphorus ions to form saturable absorbers. The characteristics of the lasing threshold current increase and the change in the optical spectrum have been investigated as a function of the ion fluence. Based on existing models for the formation of point defects in solids, a theory has been derived that effectively describes these laser parameters, as well as radiation-induced losses, as function of the ion fluence. The lasing threshold current of the laser diodes increased up to more than four times due to ion implantation, accompanied by a wavelength shift of more than 30 nm to the blue. Bistability for optical injection is observed.