heat transfer in solid, pulse

Hi all,

I am simulating pulsed laser material interaction. When th pulse duration is in milisecond range, I would get reasonable resutls. I mean as it would be expected the heat will be dropped down in off time of pulse. However, when I go to nanosecond and microsecond range, the heat won't drop down in off time (see attached figures).

I highly apprecaite if anyone has any suggestion.