Effect of scattering in InGaAsP semiconductor diode lasers

The amount of stimulated emission scattered in or near the active region of semiconductor diode lasers has been measured for over thirty 1.3-μm InGaAsP diode lasers of three structures--gain-guided, planar buried heterostructure (PBH), and arrowhead buried crescent (ABC)--using spatially and polarization-resolved electroluminescence. Plots of the degree of polarization along the length of a typical PBH and gain-guided laser are shown. Scattered TE polarized laser emission results in an increase in the degree of polarization. The scattering results have been compared and correlated with the measured spectral output of the lasers. The spectral output of lasers that have scattering centers tends to be more single mode than for lasers with little or no scattering. Also, the amount of scattering is found to be structure dependent. A theoretical model has been developed to examine the effect of internal scattering on the spectral output of InGaAsP diode lasers. The model considers the effect of a scattering center located in or near the active region. It is found from calculations based on the model that scattering centers alter greatly the spectral output of diode lasers.