Is it possible to create a laser beam using sunlight that generates a wavelength of about 500nm? Someone  else on this site inquired about how to create a laser from sun light. There were many ideas on this, but they were all based on DIY ideas. I am more specifically looking into creating a laser beam of 500 nm using sunlight since the sun emits most of its energy around that range. How would you capture the light in order to focus it into a beam? I would like to add some clarification based on the answers I am recieving. I am trying to focus sunlight into a laser so I can then aim it at a PPLN crystal. These crystals need a laser in order to be able to work, therefore I must modify sunlight into a beam. It must be in the form of a laser because I cannot amplify the frequency of sunlight until it has the laser-like features making it coherently phase matching. There must be two photons perfectly in phase in order to be paired together to double frequency.
 A: The easiest way is to buy some photovoltaic panels, and use them to power a green laser pointer that you buy from the store.
Laser light isn’t focused light, or even really monochromatic light (although laser beams are frequently focused, and are generally quite monochromatic). Laser light is coherent, which means that the electric and magnetic fields everywhere in the laser beam are oscillating in phase with each other. In general, coherent laser light is produced in some resonant medium which amplifies one wavelength while suppressing others. (“Laser” began as an acronym, for “light amplification by stimulated emission of radiation.”)
Compare with sound. Laser light is like a single musical note, with all of the power in a single frequency/wavelength of oscillation.  White light is like crowd noise, or the sound of the surf at a beach. You can’t extract a single note by listening to the beach noise and throwing away most of the frequencies.
Note that you can extract highly monochromatic light from sunlight, by being clever with prisms and diffraction gratings. But monochromatic sunlight is still not coherent. The technical phrase might be that the “coherence length” of a ray of sunlight is always small compared to any interesting experiment.
A: There have been a variety of solar pumped lasers, including the idea of putting them on satellites. The critical component is often the solar concentrator to excite the gain medium.  The other issue is much of the solar spectrum is wasted, and light not absorbed by the laser rod or gain medium is wasted or creates a heat problem. So from a fundamental point of view, it can be done, but usually the question is why would you want to do it? Other than it kind of interesting and neat to do, since most other ways of pumping lasers are more efficient.
A recent paper tries to get around having a complicated solar concentration system by having a dye surrounding, an optical fiber that would act as the laser. The light collected from the sun pumps the dye, the dye emits light that more efficiently pumps the optical fiber, and the laser light comes out of the optical fiber.
But if you look around for other solar pumped lasers you will find a variety of approaches, using a variety of solar concentration techniques like fresnel lenses, or parabolic concentrators etc.
A: The problem with Sun light pumped lasers is that Sun light is very dilute, but several ways to concentrate it in order to achieve the lasing threshold have been proposed. There is a recent proposal based on the antenna complexes of bacterial photosynthetic organisms: "Bio-inspired natural sunlight-pumped lasers". Such systems absorb dilute sunlight over a hierarchy of energy scales and could efficiently funnel this energy to a low energy lasing state.
