Ruby laser

A solid-state laser whose gain medium is chromium-doped sapphire. It typically emits pulsed red light at 694.3 nanometers.

Al₂O₃:Cr³⁺: Sapphire crystals containing chromium ions that replace some aluminum ions in the crystal lattice. These chromium ions provide the transitions responsible for ruby laser emission.
Theodore Maiman: An American physicist who built the first functioning laser in 1960. Maiman demonstrated laser action in a chromium-doped ruby crystal.
Laser rangefinder: An instrument that estimates distance by measuring the travel time or phase of laser light reflected from a target. Ruby laser pulses served in early rangefinders because they could deliver high peak power.
Nd:YAG laser: A solid-state laser that uses neodymium-doped yttrium aluminum garnet as its gain medium, commonly emitting near-infrared light at 1064 nanometers. Nd:YAG lasers generally offer more efficient operation and greater versatility than ruby lasers.
Optical pumping: The excitation of atoms or ions by light to create a population inversion or other nonequilibrium state. A flashlamp pumps chromium ions into excited states before the laser pulse.
Hughes Research Laboratories: A California research laboratory founded by Howard Hughes and known for work in aerospace, electronics, and lasers. Maiman built and operated the first ruby laser at this laboratory.
Laser tattoo removal: A medical procedure that uses laser pulses to break tattoo pigments into smaller particles for removal by the body. Q-switched ruby lasers target dark and blue-green tattoo pigments.
Helium–neon laser: A gas laser that commonly emits continuous red light at 632.8 nanometers. Unlike ruby lasers, helium–neon lasers are typically low-power continuous sources.
Population inversion: A condition in which more particles occupy an excited energy state than a lower-energy state. The ruby crystal must reach this condition for stimulated emission to amplify light.
First laser: The first device to produce coherent light by stimulated emission, demonstrated by Theodore Maiman in 1960. The first laser was a ruby laser, establishing the device’s place in laser history.

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