LAUSR

For the first time, we obtained the photoreflectance spectra in single-layer samples of porous silicon with 13 μ m thick in the 550–1000 nm spectral region. To describe the observed reflection and photoreflectance spectra, we use a theory of multiple-beam interference, taking into account the strong absorption of Si in this spectral region. We show that, under the action of a laser radiation with a wavelength 532 nm of 30 mW power and pulse duration 3 ms, the change in the refractive index δn reaches values of the order of 10 − 5 , and this takes place due to the thermal nonlinearity of the refractive index. We show that photoreflectance spectroscopy can be used to measure the thermo-optic coefficients of porous silicon.