The topical properties of oxidized free-standing porous silicon films excited by a cw laser have been investigated. It is found that samples oxidized at 800-950 deg C show a strongly superlinear light emission at an excitation intensity of approx 10 W/cm~2. This emission has a peak at 900-1100 nm and shows a blueshift as the oxidation temperature is increased. These samples also show a very large induced absorption, where the transmittance is found to decrease reversibly by <=99.7percent. The induced absorption increases linearly with increasing pump laser intensity. Both the superlinear emission and the large induced absorption are quenched when the samples are attached to materials with a higher thermal conductivity, suggesting that laser-induced thermal effects are responsible for these phenomena.
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