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Green TV Page 11

Technology to create the green light. An infrared laser diode at 808 mm is used to pump a crystal of neodymium-doped yttrium vanadium oxide or neodymium-doped yttrium aluminum garnet  and induces it to emit 281.76 THz (1064 mm . This deeper infrared light is then passed through another crystal containing potassium, titanium and phosphorus (KTP), whose non-linear properties generate light at a frequency that is twice that of the incident beam (563.5 THz); in this case corresponding to the wavelength of 532 mm ("green"). 

Other green wavelengths are also available using DPSS technology ranging from 501 mm to 543 mm. Green wavelengths are also available from gas lasers, including the Helium-neon laser (543 mm), the Argon-ion laser (514 mm  and the Krypton-ion laser (521 mm and 531 mm), as well as liquid dye lasers. 

Green lasers have a wide variety of applications, including pointing, illumination, surgery, laser light shows, spectroscopy, inter hydrometry, fluorescence, holography, machine vision, non-lethal weapon sand bird control.

 Verdigris is made by placing a plate or blade of copper, brass or bronze, slightly warmed, into a vat of fermenting wine, leaving it there for several weeks, and then scraping off and drying the green powder that forms on the metal. 

The process of making verdigris was described in ancient times by Pliny. It was used by the Romans in the murals of Pompeii, and in Celtic medieval manuscripts as early as the 5th century AD. It produced a blue-green which no other pigment could imitate, but it had drawbacks; it was unstable, it could not resist dampness, it did not mix well with other colors, it could ruin other colors with which it came into contact., and it was toxic. 

Leonardo Advance, in his treatise on painting, warned artists not to use it. It was widely used in miniature paintings in Europe and Persia in the 16th and 17th centuries. Its use largely ended in the late 19th century, when it was replaced by the safer and more stable chrome green.