In the last few years, silicon photonics has been characterized by a wide range of applications in several fields, from communications to sensing, from biophotonics to the development of new artificial materials. In this communication, we report a review of the main results obtained in our laboratories in design, fabrication and characterization of new silicon-based optical structures and devices, including metamaterials, photodetectors, raman light amplifiers, and porous silicon based bio-chemical sensors and biochips. Future perspectives in integration of silicon based MEMS and MOEMS are also presented.