Micro-lenses with well-defined optical parameters are generated on polymeth
ylmethacrylate (PMMA) substrates doped with diphenyltriazene (DPT) by contr
olled use of a swelling effect generated under conditions of subablative ex
cimer laser illumination. The surface profiles depend on the laser spot siz
e and energy density. A sensitively balanced combination of matrix softenin
g, substrate volume expansion due to photochemical nitrogen release, and su
rface tension is responsible for the final shape of the lenses. Complete ar
rays of identical lenses with 15 mu m diameters and a focal length of 30 mu
m are produced by irradiation of (0.25 wt. %) DPT-PMMA with a single laser
pulse at a wavelength of 308 nm and a fluence of 3J/cm(2) It is shown expe
rimentally and theoretically that appropriate volume expansion is possible
without introducing internal light scattering due to the formation of small
bubbles.