time scale issue when using optical pulse

Dear All

Now I have an optical pulse which lasts a few of micro seconds, while the peak occurs at a few of femto seconds after onset of the pulse. Temperature reaches a high value at the peak and gradually reduces back to room temperature at the end of the pulse. I want to see the temperature variation along with the pulse, which means that I need to plot temperature at femto second scale, pico second scale, nanosecond scale, and microsecond scale. At this moment, what I did is to set up a study 1 for femto second period first. Then setting up a study 2 for pico second scale whose initial values are the last solution of femto second period. Then setting up a study 3 for nano second period whose initial values are the last solution of pico second period. Therefore, I need to solve four times in sequence in order to cross the femto second to micro second scale. I did try to defind time range as 0:a few of femto seconds:a few of micro seconds in order to use only one study to get the all solution, but obviously it is beyond of the memory limits. Can anyone suggest a better way to find out the temperature variation along with such a hugh time scale by only solving the model once? Many thanks.

best regards
Lei