Stripe-geometry Pb1-xSnxTe diode lasers

In order to avoid parasitic modes that frequently occur in conventional rectangular lead-chalcogenide diode laser structures, stripe junction lasers emitting at about 11 μm at 4.2 K have been fabricated from vapor-grown Pb0.88Sn0.12Te. Measurements of spectra, polarization, mirror illumination patterns, and far-field patterns provide conclusive evidence that these lasers emit in a fundamental spatial transverse mode. The emission spectra of the stripe lasers consist of regularly spaced modes corresponding to the longitudinal cavity with an effective index of refraction of 7.1. The measured width of the emitting region closely corresponds to the junction width both for the 50- and 100- μm-wide stripe lasers used. The depth of the emitting region perpendicular to the junction plane was measured to be approximately 50 μm in all of the lasers. As2S3dielectric coatings of various optical thicknesses have been sequentially applied to one end face in order to evaluate the gain and loss parameters of the active region from the threshold variation with reflectivity. Loss parameter values of 12-54 cm^-1, gain parameter values of 0.084-0.24 cm/A, and internal quantum efficiencies of 0.013-0.055 are deduced from these measurements. In addition, the antireflection coating produced as much as a fourfold increase in output power at currents above threshold.