  We demonstrate lasing mode selection in nearly circular semiconductor
microdisks by shaping the spatial profile of optical pump. Despite of strong
mode overlap, adaptive pumping suppresses all lasing modes except the targeted
one. Due to slight deformation of the cavity shape and boundary roughness, each
lasing mode has distinct emission pattern. By selecting different mode to be
the dominant lasing mode, we can switch both the lasing frequency and the
output direction. Such tunability by external pump after the laser is
fabricated enhances the functionality of semiconductor microcavity lasers.
