<title>TE/TM cross-polarization laser diodes using tensile-strained quantum wells</title>

Abstract

Polarization characteristics of TE/TM cross-polarization semiconductor laser diodes are discussed in this paper. Broad area lasers fabricated from tensile strained In0.5+(delta )Ga0.5-(delta )P/(AlGa)0.5In0.5P quantum well laser structures oscillate in TE/TM dual polarizations. Polarization dominance changes from TE to TM as the cavity length of the laser is increased from 250 micrometers to 650 micrometers. The polarization-dependent gain property of a tensile-strained quantum well laser is analyzed from a simple theoretical model. In a slightly tensile strain quantum well, where light-hole and heavy-hole ground states are nearly degenerate in the valence band due to the strain and quantization effect, gain is provided for TM and TE modes simultaneously, and the two mode gain curves cross at certain injection level. Polarization switching is made possible by changing the threshold gain of the laser. The threshold gain dependent polarization switching is utilized to fabricate closely spaced independently-addressable dual beam cross polarization lasers. Results on 650 nm broad area dual beam cross polarization laser are presented. For dual polarization infrared lasers, a dual quantum well structure in which gains for TE and TM modes are provided by lattice-matched and tensile-strained quantum wells separately is designed. Eight-hundred-thirty-five nm broad area laser fabricated from a GaAs and GaAs0.95P0.05 dual quantum well structure oscillating in TE/TM dual polarizations is demonstrated.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.