  The underlying physics and detailed dynamical processes of the free space
beam excitation to the asymmetry resonant microcavity are studied numerically.
Taking the well-studied quadrupole deformed microcavity as an example, we use a
Gaussian beam to excite the high-Q mode. The simulation provides a powerful
platform to study the underlying physics. The transmission spectrum and
intracavity energy can be obtained directly. Irregular transmission spectrum
was observed, showing asymmetric Fano-type lineshapes which could be attributed
to interference between the different light paths. Then excitation efficiencies
about the aim distance of the incident Gaussian beam and the rotation angle of
the cavity were studied, showing great consistence with the reversal of
emission efficiencies. By projecting the position dependent excitation
efficiency to the phase space, the correspondence between the excitation and
emission was demonstrated. In addition, we compared the Husimi distributions of
the excitation processes and provided more direct evidences of the dynamical
tunneling process in the excitation process.
