  We present a quantum dynamic study on organic lasing phenomena, which is a
challenging issue in organic optoelectronics. Previously, phenomenological
method has achieved success in describing experimental observation. However, it
cannot directly bridge the laser threshold with molecular electronic structure
parameters and cavity parameters. Quantum dynamics method for describing
organic lasing and obtaining laser threshold is highly expected. In this
Letter, we first propose a microscopic model suitable for describing the lasing
dynamics of organic molecular system and we apply the time-dependent
wave-packet diffusion (TDWPD) to reveal the microscopic quantum dynamical
process for the optical pumped lasing behavior. Lasing threshold is obtained
from the onset of output as a function of optical input pumping. We predict
that the lasing threshold has an optimal value as function of the cavity volume
and depends linearly on the intracavity photon leakage rate. The
structure-property relationships between molecular electronic structure
parameters (including the energy of molecular excited state, the transition
dipole and the organization energy) and the laser threshold obtained through
numerical calculations are in qualitative agreement the experimental results,
which also confirms the reliability of our approach. This work is beneficial to
understanding the mechanism of organic laser and optimizing the design of
organic laser materials. TOC
