However, the Cr 3+ ions are larger and have electron orbitals in different directions than aluminium. When a chromium atom replaces an occasional aluminium atom, it too loses 3 electrons to become a Cr 3+ ion to maintain the charge balance of the Al 2O 3 crystal.

Sapphire, ruby, and pure corundum are α-alumina, the most stable form of Al 2O 3, in which 3 electrons leave each aluminium ion to join the regular octahedral group of six nearby O 2− ions in pure corundum this leaves all of the aluminium ions with a very stable configuration of no unpaired electrons or unfilled energy levels, and the crystal is perfectly colorless. T he operation of the ruby laser is based on optical and fluorescence properties of ruby which allow to obtain a population inversion in a three-levels laser scheme. The invention of the Ruby Laser by Theodore Maiman in 1960 initiated the era of photonics technologies. This emission is interesting because of its intensity, its narrow emission line (responsible for the luster and the color of the crystal) and because of the relatively long fluorescence lifetime. The crystal emits strong red fluorescence. In the cover image and in the image aside we show our crystal excited with a 400 nm violet laser diode.

We show that interesting results can easily be obtained even with our DIY low-cost instrumentation. In this post we study the fluorescence of ruby and in particular its lifetime. Abstract : ruby has a red spectacular fluorescence under violet or blue-green radiations with a doublet spectrum at 692.80 and 694.30 nm, which appears as a single line.

Ruby process monitor