Narrowest wavelength laser

Helium-Neon (HeNe) lasers can be configured to commonly produce light at 632.8nm wavelength that is only 0.002 nm in bandwidth. This gives a very pure spectral emission of red, and is well over 10,000 times narrower than the spectral width of a laser diode commonly used in pointers, CD players, etc. This type of laser was one of the first gas discharge lasers to be made both in the laboratory and commercially. Even with advances in laser technology today, the humble HeNe laser is found at the heart of many advanced scientific instruments.