Two-photon excitation of luminescence in pyrolytic silicon nanocrystals

Two-photon-excited luminescence after femtosecond near-infrared (NIR) excitation was observed in chemically oxidized silicon nanocrystals (Si-nc) produced by laser-assisted pyrolysis of silane. The luminescence time decay and emission spectrum resulted in good agreement with those after blue excitation. The underlying two-photon absorption coefficient was also measured by the open-aperture z-scan technique, obtaining a value of 12.5 cm/GW, which is intermediate between the values reported in the literature for bulk silicon and for very small Si-nc.