Femtosecond Z-scan investigation of nonlinear refraction in surface modified PbS nanoparticles
Li, H.P. Liu, B. Kam, C.H. Lam, Y.L. Que, W.X. Gan, L.M. Chew, C.H. Xu, G.Q.
Li, H.P.
Kam, C.H.
Lam, Y.L.
Que, W.X.
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Abstract
The third-order optical nonlinearities of surface modified PbS nanoparticles have been measured using the Z-scan technique with femtosecond laser pulses at 780 nm wavelength. The samples studied are the nanoparticles in micro-emulsion with the PbS concentration ranging from 0.3 × 10-3 to 1.9 × 10-3 M (mol/l). A Z-scan analysis method based on the Huygens-Fresnel (H-F) propagation integral is employed to extract the nonlinear refractive index from the experimental Z-scan data with a large nonlinear phase shift. The nonlinear refractive index of the PbS nanoparticles in microemulsion is found to increase linearly with the PbS concentration. The highest concentration microemulsion gives a nonlinear refractive index of -4.7 × 10-12 cm2/W, which is approximately 3 orders of magnitude higher than those of commercially available bulk semiconductors, such as ZnS and CdS. In addition, nonlinear absorption in these samples remained unmeasurable up to 0.9 GW/cm2. The mechanisms responsible for the observed large refractive nonlinearity are discussed.
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Optical Materials
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Date
2000-08-04
DOI
10.1016/S0925-3467(00)00003-3
Type
Article