Formation of microscopic coloured oxide dots on the titanium foil surface irradiated by a laser

Experiments are performed on the formation of coloured dots of a submillimetre size on the titanium foil surface irradiated by pulsed IR lasers. It is shown that the parameters of laser pulses can be selected so that the dots produced on the titanium foil surface will change their colour from yellow to blue with increasing exposure time. The threshold laser power densities required for the formation of contrast coloured dots on the titanium foil surface irradiated by laser pulses with low repetition rates are estimated as ~1.5 × 10³ J cm^-2 for a 1.73-μm Xe laser and ~2.3 × 10³ J cm^-2 for a 10.6-μm CO₂ laser.