# History of the Laser

| Lasers are one big success story - and an embodiment of Feynmans famous sentence:
|  | "There are certain situations in which the peculiarities of quantum mechanics can come out in a special way on a large scale".
|  | It is not necessary to to emphasize how important Lasers are to all of us - to the scientist, the patient in a hospital, the consumer listening to her discs, the supermarket cashier, the geometer - and just about everybody else. It should be quite clear.
|  | It is, however, quite necessary to emphasize that Lasers (and, of course, all of solid state electronics), are purely quantum mechanical devices, because this is simply not known to the "people in the street" (including those in suits; and this says something about the state of general eduction in this country).
| Here are a few milestones in the development of the Laser.

| The first major date is 1916, when Albert Einstein introduced the concept of stimulated emission.
| It took till 1953 to demonstrate stimulated emission experimentally. This was achieved by Gordon, Zeiger and Townes.
|  | The researchers used the two lowest vibrational energy levels of ammonia molecules and obtained a very narrow emission line at 12.6 mm, i.e. in the "micro"wave region.
|  | This is where the name "Maser" comes from.
|  | Follow-up on the "Maser" finally led to Nobel prizes shared between Townes and the Russians Basov and Prokhorov in 1964.
| Meanwhile, however, Maiman produced the first optical Maser, as the Laser was originally called in 1960.
|  | The light came from Cr3+ ions fixed in an Al2O3 crystal - a ruby in other words, at a wavelength of 694,3 nm.
|  | Pumping took place with an intense light source, and the Laser only emitted a short pulse.
| 1962 the first semiconductor Laser was produced, by N.G. Basov.

With frame

5.3.1 Light Sources

© H. Föll (Advanced Materials B, part 1 - script)