  The availability of microlasers with highly directional far-field
characteristics is crucial for future applications. To this end we study the
far-field emission of active microcavities with spiral shape using the
Schroedinger-Bloch model. We find that they can provide directional emission
under the conditions of (i) pumping along the resonator boundary and (ii) for
specific resonator geometries. We systematically study the far-field
characteristics under variation of the pumped area and the cavity geometry, and
identify an directionality-optimized regime. Our results consistently explain
previously obtained experimental results.
