Nonlinear optical properties of silicon nanoclusters

The nonlinear optical properties of small nano-scale semiconducting silicon was investigated. Atomic force microscopy (AFM) was used to measure the size distribution of the clusters in three major size regions: Region I had the smallest size clusters in the range of 3-43 nm with a mean value at 7 nm and standard deviation of 3 nm; the `medium' clusters in Region II ranged between 5-42 nm with a mean value at 11 nm and standard deviation of 8 nm; and Region III has cluster size distribution from 15-85 nm with a mean value at 50 nm and standard deviation of 22 nm. The clusters of average size of 11 nm absorbed strongly at λ = 355 nm and possessed Re{χ⁽³⁾}>0 whereas clusters of all sizes adsorbed strongly at λ = 532 nm and exhibited Re{χ⁽³⁾}<0.