Coherent emission from ultrathin-walled spiral InGaAs/GaAs quantum dot microtubes

We report on the achievement of strong coherent emission from GaAs-based single-walled spiral microtubes, wherein photons are localized in an ultrathin (approximately lambda/25) region embedded with self-organized InGaAs quantum dots. The emission spectra measured at 300 K are characterized by a regular sequence of sharp optical modes with a maximum Q factor of approximately 2500 and separation of approximately 7 meV. The three-dimensional confinement of photons is made possible by the epitaxially smooth tube surface as well as an engineered surface geometry, achieved using a single photolithography step. The experimental results are analyzed using an equivalent planar dielectric waveguide model.