Emission efficiency of bulk-silicon is very low due to its indirect-gap of energy band. However, it is interesting that the enhanced emission has been observed in the micro-cavities array fabricated by using femtosecond (fs) pulsed laser, in which the stimulated emission characteristics occur after annealing for suitable time in the photo-luminescence (PL) measurement at room temperature. The results of experiment and calculation demonstrated that the enhanced emission may be originated from the Si quantum dots embedded in the micro-cavities prepared by fs pulsed laser. Here, the direct-gap of energy band appears after annealing due to the Heisenberg principle related to ⊿k–1/⊿x in quantum system of nanostructures. The PL intensity obviously increases on the Si quantum dots growing with annealing for better crystallization, in which the external quantum efficiency is higher than 40 % near 760 nm. A new kind of emission source of the micro-cavities array in visible wavelength has been built on silicon wafer, in which the Si quantum dots play a main role for enhancement of emission. It should have a good application in optical integrated chip based on silicon, such as emission cells built on Si chip.