1.1 The inspiration of the issue
The potential of lasers for producing energy is evident and well-known. Listed here are some examples of applications: space communication, energy support in space, efficient energy transfer over large distances, efficient laser pumping for chemical reactions to mention just a few.
If the laser energy could be produced with an efficient conversion rate, it would be economically good. For some applications, direct solar pumping seems to be advantageous. Depending on conversion efficiency, complexity, reliability, or other conditions, it could be the preferable pump source for a laser and superior to all other methods, including electrical pumping by photo cells. This holds, for example, for an autark energy satellite, where the solar spectrum is split. The spectrally adapted part supplies the energy for the laser and the rest is used for driving solar cells that provide the energy for the peripheral systems.
It is possible that solar pumped lasers will become a cheap source for coherent and high power radiation. It is a dream of mankind to convert the sunlight, which is an incoherent, broadband radiation into laser radiation which is coherent and monochromatic [1].
Perhaps the first inspiration for producing a coherent monochromatic light from the sun was taken from the old Egyptian scripts. One icon shows the Pharaoh Akhenaton with his family praying to his god Aton, symbolized by the solar disc from which fine beams radiate to waiting hands as shown in Fig 1-1.