| The single crystal Si is an undirected band gap semiconductor and its energy gap is 1.11ev. As the luminescent material at the application in photoelectric field single crystal Si is limited. Since 1990 intense visible photoluminescence of porous silicon was found by the English scientist Canham for the first time and explained by quantum confinement effect, porous silicon have been attracted many scientists attention in the world. Later, the discovery of all colures photoluminescence and electric-luminescence from porous silicon and the encouraging progress in fabricating porous silicon based light-emitters has cast a new light on Si-based opt-electronics. In addition, with the deep-going of the nonlinear materials, nanometer cluster induced scientists' interests for the special scale effect. This paper is divided into five parts. In the paper, The preparation, photoluminescence mechanism and third-order nonlinear of porous silicon are mainly introduced.In the first chapter, a brief history, background, preparation and formation of porous silicon are provided and several effective luminescent models are also introduced as well. Then the experiment results showed that the mechanism of the photoluminescence of porous silicon was ascribed to the co-effect of quantum confinement and the surface materials of porous silicon. The application of porous silicon is anticipated.In the second chapter, nonlinear optics is introduced briefly. Concept, investigating area and the main phenomenon of the nonlinear optics are presented. Z-scan technologyas one simple means of measuring the third-order nonlinear susceptibility is also introduced. Through connecting experiment results with theories the third-order nonlinear refractive index and nonlinear absorption coefficient are calculated.In the third chapter Porous silicon was prepared by pulsed and dc electrochemical etching methods under the equivalent etching condition. The SEM and the PL observation showed that the surface of porous silicon prepared by pulsed etching was more uniform and the Si particles were smaller. The intensity of PL formed by pulsed etching method was enhanced and the peak had blue shift comparing that formed by dc electrochemical etching method. At the same time, it was observed that the smaller the dimension of the Porous silicon, the broader energy gap of the Porous silicon. Our experiment results showed that the PL mechanism of porous silicon accorded with the mechanism of quantum confinement effect.In the fourth chapter the PL and FTIR spectra of porous silicon as-prepared and stored in atmosphere for one month were measured. The formers' PL only had single peak with lower energy while the latter appeared double peaks with a higher energy. Through comparing the FTIR spectra of the two samples we found Si-O-Si and O-Si-H bonds appeared in the FTIR spectra of the latter sample. For other sample which also appeared two peaks the change of its two peaks varied with the temperature was observed. The higher energy peak remained stable with the temperature change. However the intensity of the lower energy peak was enhanced and the peak position had a blue-shift with the rise of temperature. Our experiment results showed that the photoluminescence mechanism of Porous silicon was ascribed to the co-effect ofquantum confinement and the surface materials of Porous silicon.In the fifth chapter, the real and imaginary parts of third-order nonlinearsusceptibility x(3) been measured for porous silicon dispersed into CCl3 solution. Measurements had been performed under a ps laser excitation at 1064nm and 532nm using the Z-scan technique. The real part of x(3) showed positive nonlinearity for bothmeasured wavelength. Nonlinear absorption evidently existed that attributed to saturation absorption process. The absolute value of x(3) at 1064nm and 532nm wereon the order of 10-13esu and 10-14esu respectively. Our experiment results show that the big x(3) of porous silicon is related to quantum confin...
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