Two-channel optical pyrometry of metals irradiated by picosecond laser pulses

We have used two-channel optical pyrometry to study the surface color temperature versus time profiles of aluminum and tungsten irradiated with 100 ps, 5 ns, and 60–70 ns duration pulses of Nd-glass laser in the fluence range of 0.5–15 J/cm2. We demonstrate that at fluences of several J/cm2 the temperatures of both materials can rise above 5000 K. The maximum observed cooling rates are 5×1010 K/s, two orders of magnitude less than the theoretical estimation. The importance of these results for the laser annealing experiments on metals and alloys is discussed.