Optical gain anisotropy in serpentine superlattice nanowire-array lasers

We report optical gain measurement from a serpentine superlattice nanowire-array laser sample, grown by molecular beam epitaxy on a 2°-off (100)GaAs vicinal substrate. Gain spectra, obtained from in-plane ridge-waveguide lasers with stripes either parallel or perpendicular to the nanowire arrays at 1.4 K, showed that the optical gain for the TM mode became greater than that of the TE mode when the optical cavity was placed along the nanowire direction. This provides strong evidence that the lateral quantum confinement in the serpentine superlattice is stronger than the vertical quantum confinement.