  We examine generation dynamics of coherent phonons (CPs) in both of polar and
non-polar semiconductors -- such as GaAs and Si -- based on a
polaronic-quasiparticle (PQ) model. In the model concerned, the PQ operator is
composed of two kinds of operators. One is a quasiboson operator -- defined as
a linear combination of a set of pairs of electron operators -- and the other
is a longitudinal optical (LO) phonon operator. The problem of transient and
non-linear Fano resonance (FR) is tackled in particular; the vestige of this
quantum interference effect was observed exclusively in lightly $n$-doped Si
immediately after carriers were excited by an ultrashort pulse-laser [M. Hase
et. al., Nature 426, 51 (2003)], though not observed yet in GaAs. It is shown
that the phonon energy state is embedded in a continuum state formed by a set
of adiabatic eigenstates of the quasiboson. This result implies the possibility
of manifestation of the transient FR in the present optically-non-linear
system.
