Nonlinear absorption in silicon and the prospects of mid‐infrared silicon Raman lasers

Abstract

Abstract We present the first experimental results of nonlinear absorption in silicon at the mid infrared wavelengths. Nonlinear losses due to two‐photon and free‐carrier absorption that are found to degrade near infrared silicon Raman devices become negligible at photon energies less than half the bandgap (i.e., λ > 2.2 µm in wavelength). Moreover, the low loss window for linear absorption in silicon extends from 1.2 to 6.5 µm. These factors along with the excellent thermal conductivity and high optical damage threshold renders silicon an ideal material for building Raman lasers and amplifiers that operate in the mid infrared wavelengths. This new technology will expand the application space of silicon photonics beyond data communication and into biochemical sensing, laser medicine, and LIDAR. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)