Near-field spectroscopy of porous silicon microcavity samples

Near-field optical spectroscopy has been used to investigate photoluminescence features of porous silicon microcavity samples with a subwavelength space resolution. The emission is found to be markedly dependent on the lateral position, with the presence of relatively narrow spectral features peaked at different wavelengths in the range 610-690 nm. Furthermore, the spectrum obtained by summing up spectra taken at different sampling points (relative displacement similar to100 nm) recovers the standard (macroscopic) photoluminescence spectrum of porous silicon, except for the presence of a dip around the resonance wavelength of the microcavity resonator.