Effect of delay of the thermocapillary response of a transparent liquid layer during laser heating of the absorbing substrate

The effect of delay in the thermocapillary response of a transparent liquid layer on an absorbing substrate during its heating by a laser beam is discovered. The response is an interference pattern formed on a screen placed in the beam cross section by the beam reflected from a thermocapillary dip. It is found that the delay time of the response of a thin (h < 1.8 mm) layer of a liquid in a viscosity range of 3–6 mPa s to a 20.9-mW exciting beam from a He-Ne laser (λ = 633 nm) is proportional to the squared layer thickness with a proportionality factor depending on the viscosity and thermal diffusivity of the liquid.