blue and green laser pointer

(http://www.kitlaser.com/50mw-100mw-green-laser-p-hard-aluminum.html)

Schawlow and Townes had agreed to an open-resonator blue laser pointer design – apparently unaware of Prokhorov’s publications and Gould’s unpublished laser work.Simultaneously, at Columbia University, graduate student Gordon Gould was working on a doctoral thesis about the energy levels of excited thallium. When Gould and Townes met, they spoke of radiation emission, as a general subject; afterwards, in November 1957, Gould noted his ideas for a “laser”, including using an open resonator (later an essential laser-device component). Moreover, in 1958, Prokhorov independently proposed using an open resonator, the first published appearance (in the USSR) of this idea. Elsewhere, in the U.S.

Albert Einstein was the first to have the idea of stimulated emission that could produce a green laser pointer.Laser pointers are used by people to point at a place on a map or diagram. For example, lecturers use them. Also, many people like to play with laser pointers. Some people have pointed them at aircraft. ThIs is dangerous, and it is also illegal in many countries. At first, people succeeded in making masers and later figured how to make shorter visible wavelengths.People have been arrested and prosecuted for this crime. From that point many years were spent to see if the idea worked.

(http://www.kitlaser.com/80mw-100mw-200wm-aluminum-alloy-laser-p.html)