On the road to silicon-nanoparticle laser

To satisfy the need for CPU clock frequencies continuous increase, optical data transmission process integrated within silicon chips is required. Practical optical amplification in silicon is therefore very desirable. Unfortunately, bulk silicon is an indirect bandgap semiconductor with very low light-emission efficiency. To overcome this problem, the stimulated Raman scattering has been successfully employed for light amplification and lasing in silicon. Due to the two-photon absorption nonlinear optical loss, this scheme was initially working only in a pulsed operation mode. Very recently, an improved design has been allowed also for the continuous operation. However, this encouraging development still contains a major drawback-a need for an external optical pumping. It seems that this problem might be overcome by switching from the bulk silicon to its properly prepared nanocrystalline form provided a reasonably good electroluminescence can be achieved. An intensive research is under way with some first promising results already in the pipeline. (c) 2006 Elsevier B.V. All rights reserved.