To stimulate a high threshold level solid state laser, a light source of high optical
stimulating power is needed. In the classical laser systems, pulsed or cw- flashlamps, while in
the modern ones diode lasers are used. Although the latter are very efficient, they are
expensive. The total efficiency of the flashlamp-pumped lasers is less than 4 % (50 %
efficiency of the flashlamp times 8 % efficiency of the optical laser system). The efficiency
of the diode-pumped lasers lies between 35 % and 50 % depending on the electrical input
power.