A new approach to the problem of preparation of laterally structured lumine
scent porous silicon is proposed. The effect is based on the photosensitivi
ty of chemical etching of silicon. Contrary to the other technique recently
reported where the porous layer was modified with light assisted chemical
dissolution, a one stage anodisation-free process is used. Any desired late
ral structure can be produced, depending on the illumination pattern, which
is defined by optical imaging. A 2D micro-array was prepared as an example
of this fast mask-free technology with an accuracy of 5 mu m. Samples have
a broadband visible photoluminescence centred at 680 nm when illuminated w
ith UV or blue light. The results are analysed to determine the possible ac
hievable accuracy of the technique and to improve our understanding of the
mechanism of light assisted etching.