Ultrafast optical processes in new Cu-Fe-S nanoparticles

Nonlinear optical effects in surface oxidized CuFexSy (x equals 1,2, y equals 2,3) nanoparticles incorporated in polymeric film are studied. Surface oxidation of CuFeS2 and CuFe2S3 nanoparticles results in appearance of the additional absorption band with maximum at 1.03 and 1.15 micrometer, respectively. Bleaching of this additional absorption band in CuFe2S3 particles and the induced absorption in all studied samples after picosecond laser excitation take place. An energy level scheme for CuFeS2 and CuFe2S3 nanoparticles with long-lived trap levels in the band gap is proposed and origin of additional absorption is discussed. Characteristic times for career relaxation from conduction band to these trap levels are approximately 25 plus or minus 5 ps for CuFe2S3 and approximately 70 plus or minus 10 ps for CuFeS2 oxidized nanoparticles. The relaxation of electrons from trap levels has characteristic time of more than 500 ps.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.