Porous silicon with interference characteristics was prepared by the pulsed electrochemical anodization method. The influences of current density, effective anodization time and electrolyte composition on the Fabry-Pérot (F-P) interference characteristic of porous silicon were investigated. Interferometric reflectance spectra of the porous silicon were measured using a fiber spectrometer and the corresponding optical thickness was calculated. The results show that the porous silicon can produce uniform F-P interference rings, under the condition of current density 78 mA•cm－2, effective anodization time 5 min and VHF∶VEtOH＝2∶1. The property of the films prepared under the conditions is very stable. The reflectance spectra of the porous silicon also were red-shifted from 612 to 637 nm, and the corresponding optical thickness was increased from 5864 to 6296 nm upon exposure to saturated ethanol vapor. It is feasible that ethanol vapor can be detected by F-P interference effect of the porous silicon.

Key words: porous silicon, Fabry-Pérot interference, optical thickness, sensor