Characteristic low-threshold polariton lasing of organic and inorganic microcavity systems can only be achieved with
efficient population of the lower polariton ground state. In this regard, the key role undertaken by vibronic replicas and
molecular phonon it has been shown experimentally and theoretically predicted by various works. We report here, direct
observation of critical enhancement of polariton population density in strongly coupled J-aggregate based organic
microcavities. The process highlighted in our study is manifested by discrete maxima of the angular-resolved
photoluminescence intensity and interpreted by the mediation of molecular vibrations quanta characteristic of the active
material. By measuring the reduced time scale of vibrations driven relaxation dynamics, manifested by sub 100fs buildup
times, we emphasized the efficiency of the mechanism to overcome losses channel in disordered J-aggregate systems.
Hence, the realization of amplified polariton population with improved relaxation rates paves the way for the observation
of low threshold lasing, primary step for developing room temperature organic laser sources and ultra-fast optoelectronic
devices with less fabrication complexity than their crystalline counterparts.