Near-field emission of lead-sulfide-selenide homojunction lasers

Measurements of the near-field intensity distributions of three lead-sulfide-selenide diode lasers operating near 4.8 μm have been made as a function of injection current. Localized emission in the near field exhibits peaked structure of full width from 5 to 10 μm for operation above threshold. From the dependence of the emission profiles on injection current estimates of 25 cm^-1and 0.09 cm/A are made for the distributed loss and gain coefficients for one of the lasers. Optical confinement perpendicular to the p-n junction can be explained in terms of the homojunction properties.