Under the condition of femtosecond impulsive nonlinear optical irradiation, the bright and narrowed blue emission of silicon nanocrystal was observed. This synthetic method produced very small (~ 4 nm) oxide-capped silicon nanocrystal having probably ultra small emitting core (~ 1 nm) inferred from luminescence. By controlling the stirring condition, very high efficiencies of luminescence ( 4 fold higher) were obtained compared with the other conventional femtosecond laser fragmentation methods, which was attributed to the differences in hydration shell structure during the femtosecond laser induced irreversible phase transition reaction. When we properly adjusted the irradiation times of the white light continuum and stirring condition, very homogeneous luminescent silicon nanocrystal bands having relatively sharp lineshape were obtained, which can be attributable to the luminescent core site isolated and free from the surface defects. The field of silicon semiconductor nanocrystals is one of the active research areas in which a wide range of industrial applications including solar cells, sensors, secondary battery unit, and PDT sensitizer in nanomedine have been investigated 1-8 and is also expected to have a very promising role in the future informatics like the quantum computing 9 . Especially, silicon is one of the few elements providing nontoxic, earth abundant and environmentally- friendly characters, and has dominated the microelectronics industry due to their unique physicochemical properties. Therefore, in practical applications such as optoelectronics, the fabrication of reliable and functional silicon nanocrystal having homogeneous optical properties is very important future challenge 10-22 . Until recently, considerable