Routes towards a silicon-based laser

Silicon, the material par excellence for electronics, is not used for light sources because of the lack of efficient light emitters and lasers. In this review, I will discuss the physical reasons why silicon is not a laser material and some approaches to make it lasing. I will start with bulk silicon, then I will discuss silicon nanocrystals and Er3+-coupled silicon nanocrystals, where significant advances have been made in the past and can be expected in the near future. I will conclude with an optimistic note on silicon lasing.