(Work in conjunction with G. V. Morozov,
M. Sieber and H. Waalkens
)
A new design of dielectric microcavities supporting modes with large
quality factors and highly directional light emission is presented.
The key idea is to place a point scatterer inside a dielectric circular
microdisk. It is shown that, depending on the position and the strength
of the scatterer, this design leads to highly directional modes in
various frequency regions while preserving the high $Q$-factors
reminescent of the whispering gallery modes of the microdisks without
scatterer. The design presented is very appealing due to its simplicity
which promises a simpler experimental realisation than other
microcavity
designs studied earlier on the one hand and its analytic tractability
based on Green's function techniques and self-adjoint extension theory
on the other hand.