  We propose and analyze a family of nanoscale cavities for electrically-pumped
surface-emitting semiconductor lasers that use surface plasmons to provide
optical mode confinement in cavities which have dimensions in the 100-300 nm
range. The proposed laser cavities are in many ways nanoscale optical versions
of micropatch antennas that are commonly used at microwave/RF frequencies.
Surface plasmons are not only used for mode confinement but also for output
beam shaping to realize single-lobe far-field radiation patterns with narrow
beam waists from subwavelength size cavities. We identify the cavity modes with
the largest quality factors and modal gain, and show that in the near-IR
wavelength range (1.0-1.6 microns) cavity losses (including surface plasmon
losses) can be compensated by the strong mode confinement in the gain region
provided by the surface plasmons themselves and the required material threshold
gain values can be smaller than 700 1/cm.
