Ruby laser

[1][2] Ruby lasers produce pulses of coherent visible light at a wavelength of 694.3 nm, which is a deep red color.

The rod is often placed between two mirrors, forming an optical cavity, which oscillate the light produced by the ruby's fluorescence, causing stimulated emission.

Ruby is one of the few solid state lasers that produce light in the visible range of the spectrum, lasing at 694.3 nanometers, in a deep red color, with a very narrow linewidth of 0.53 nm.

Ruby has very broad and powerful absorption bands in the visual spectrum, at 400 and 550 nm, and a very long fluorescence lifetime of 3 milliseconds.

Modern lasers often use rods with antireflection coatings, or with the ends cut and polished at Brewster's angle instead.

Curved mirrors are typically used to relax the alignment tolerances and to form a stable resonator, often compensating for thermal lensing of the rod.

The active part of the ruby is the dopant, which consists of chromium ions suspended in a synthetic sapphire crystal.

[8] Many non-destructive testing labs use ruby lasers to create holograms of large objects such as aircraft tires to look for weaknesses in the lining.

While attending a conference in 1959, Maiman listened to a speech given by Schawlow, describing the use of ruby as a lasing medium.

He found his light source when a salesman from General Electric showed him a few xenon flashtubes, claiming that the largest could ignite steel wool if placed near the tube.

Maiman realized that, with such intensity, he did not need such a highly reflective pumping cavity, and, with the helical lamp, would not need it to have an elliptical shape.

[15] In 1962, Willard Boyle, working at Bell Labs, produced the first continuous output from a ruby laser.

Unlike the usual side-pumping method, the light from a mercury arc lamp was pumped into the end of a very small rod, to achieve the necessary population inversion.