Tunable room temperature second harmonic generation in glasses doped with CuCl nanocrystalline quantum dots

Two-photon excited emission centered at 379-426 nm in photodarkening borosilicate glass doped with CuCl nanocrystalline quantum dots at room temperature has been observed. The emission is detected in the direction of the fundamental near-infrared beam. Time- and frequency-resolved measurements at room temperature and 77 K indicate that the emission is largely coherent light characteristic of second harmonic generation (SHG). An average conversion efficiency of similar to10(-10) is obtained for a 2 mm thick sample. The observed SHG can originate in the individual noncentrosymmetric nanocrystals, leading to a bulk-like contribution, and at the nanocrystal-glass interface, leading to a surface contribution. The bulk-like conversion efficiency is estimated using previously reported values of coherence length (5 mum) and bulk nonlinear susceptibility. This bulk-like conversion efficiency estimate is found to be smaller than the measured value, suggesting a more prominent surface contribution. (C) 2003 Elsevier Science B.V. All rights reserved.