Laser-induced incandescence (LII) of carbon surface is investigated with 1.06 um YAG:Nd3+ pulsed laser excitation. The experiments show that the intensity of LII or carbon surface depends on the initial temperature of the investigated sample. A method is proposed for estimation of temperature of laser-heated surfaces. The method requires measurement of LII at a fixed wavelength with a moderate variation of initial sample temperature.
In this work the possibility of laser overheating of light-absorbing surfaces of bulk carbon samples to
incandescent temperatures with the use of a moderate-power Q-switched YAG-Nd3+ laser (wavelength 1064
nm, pulse duration 20 ns, power density 3-10 MW/cm2) was studied. We observed laser-induced incandescence
(LII) of carbon surfaces and investigated its properties. When the surface was irradiated by a sequence of laser
pulses, unusual changes of LII intensity were discovered in the experiments. Also significant nonlinearity in the
dependence of LII intensity on the laser pulse power density was observed. The average temperature of
irradiated surface was estimated by approximating the experimental LII spectrum by Plank's function and by
computer simulations of laser heating of the carbon surface. For typical experimental conditions, the value of
2400 K was obtained. Both of the estimates of temperature are in a good agreement. The model, which is
proposed to explain the observed effects, is based on the equation of heat conduction. Well-known thermal and
optical properties of carbon are taken into account. The observed effects can be explained by essential nonuniformity
of heating of rough surfaces and dominant evaporation of carbon from the tops of surface asperities.