S 3

get to laser than those with short lifetimes. 3. In order to operate, a laser needs a medium with population inversion. This condition involves the energy levels, which are influenced by the temperature of the medium. Show that, for a Ruby laser A ~ 694nm. this laser cannot operate at room temperature (Assume 92 = 91 = 1). 4. Calculate the average power, peak intensity and average fluence of the following circular Gaussian