  Silicon lasers have been the most challenging element for the monolithic
integrated Si photonics. Here we report the first successful all-Si laser at
room temperature based on silicon nanocrystals (Si NCs) with high optical
gains. The active Si NC layer was made from hydrogen silsesquioxane (HSQ) that
had undergone a phase separation annealing, followed by high-pressure hydrogen
passivation. Using the nanoimprint technique, a second-order Bragg grating was
made on the active layer as the distributed feedback (DFB) laser cavity. This
Si NC DFB laser device was optically pumped with femtosecond pulses. Criteria
for lasing action, i.e., the threshold effect, the polarization dependence and
the significant spectral narrowing of stimulated emission were evidently
fulfilled, which indicated the realization of an all-Si laser.
