Preparation and non-linear optical properties of CdS quantum dots in Na2O-B2O3-SiO2 glasses by the sol-gel technique

• Published in: Journal of materials science Vol. 31; no. 2; pp. 423 - 430
• Main Authors: TAKADA, T, MACKENZIE, J. D, YAMANE, M, KANG, K, PEYGHAMBARIAN, N, REEVES, R. J, KNOBBE, E. T, POWELL, R. C
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 1996
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Ii-vi semiconductors; Nonlinear optics; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Optical susceptibility, hyperpolarizability; Optics; Physics; Inorganic compounds; Semiconductor materials; Quantum dots; Transition element compounds; Cadmium sulfides; Non linear optical susceptibility; Glass; Experimental study; Preparation; Size effect; Absorption spectra; Nonlinear optics; Sol-gel process
• DOI: 10.1007/BF01139160
• ISSN: 0022-2461

Nonlinear optical properties of CdS quantum dots embedded in the sol gel derived Na2O-B2O3-SiO2 glass matrix have been studied using nanosecond degenerate four-wave mixing (DFWM), pump-probe experiments, and time-resolved subpicosecond DFWM measurements. The concentration of CdS microcrystallites was varied from 1.4 to 10.2 wt pct while the particle size was controlled to be in the range of 3 - 6 nm in diameter so that the confinement effects could be realized. The third-order susceptibility was determined to be of the order of 10 exp -7 - 10 exp -6 e.s.u. near the resonant wavelength between 450 and 470 nm by the nanosecond DFWM and pump-probe experiments, and of the order of 10 exp -11 - 10 exp -10 e.s.u. at the off-resonant wavelength, 580 nm, by a time-resolved DFWM measurement with 400 fs laser pulse. The decay time changed from 0.5 to 50 picoseconds as a function of the size, size distribution, and number density of CdS microcrystallites in the glasses. Photodarkening reduced the optical nonlinearity of the melt-quenched samples by a factor of about 20, while it had no appreciable effect on that of the sol gel derived samples. (Author)