![]() ![]() Therefore, a He-Ne laser that has lost enough of its helium (e.g., due to diffusion through the seals or glass) will lose its laser functionality because the pumping efficiency will be too low. Without helium, the neon atoms would be excited mostly to lower excited states, responsible for non-laser lines.Ī neon laser with no helium can be constructed, but it is much more difficult without this means of energy coupling. The excited helium atoms collide with neon atoms, exciting some of them to the state that radiates 632.8 nm. ![]() ![]() The gas mixture is mostly helium, so that helium atoms can be excited. The gain medium of the laser, as suggested by its name, is a mixture of helium and neon gases, in approximately a 10:1 ratio, contained at low pressure in a glass envelope. It was developed at Bell Telephone Laboratories in 1962, 18 months after the pioneering demonstration at the same laboratory of the first continuous infrared He-Ne gas laser in December 1960. The best-known and most widely used He-Ne laser operates at a wavelength of 632.8 nm, in the red part of the visible spectrum. However, in high-power He-Ne lasers having a particularly long cavity, superluminescence at 3.39 μm can become a nuisance, robbing power from the stimulated emission medium, often requiring additional suppression. The 3.39 μm transition has a very high gain, but is prevented from use in an ordinary He-Ne laser (of a different intended wavelength) because the cavity and mirrors are lossy at that wavelength. Stimulated emissions are known from over 100 μm in the far infrared to 540 nm in the visible.īecause visible transitions have somewhat lower gain, these lasers generally have lower output efficiencies and are more costly. However, other visible and infrared stimulated-emission wavelengths are possible, and by using mirror coatings with their peak reflectance at these other wavelengths He-Ne lasers could be engineered to employ those transitions, including visible lasers appearing red, orange, yellow, and green. The 633 nm line was found to have the highest gain in the visible spectrum, making this the wavelength of choice for most He-Ne lasers. However, a laser that operated at visible wavelengths was much more in demand, and a number of other neon transitions were investigated to identify ones in which a population inversion can be achieved. The first He-Ne lasers emitted infrared at 1150 nm, and were the first gas lasers and the first lasers with continuous wave output. The best-known and most widely used He-Ne laser operates at a wavelength of 632.8 nm, in the red part of the visible spectrum. Helium–neon laser at the University of Chemnitz, GermanyĪ helium–neon laser or He-Ne laser, is a type of gas laser whose high energetic medium gain medium consists of a mixture of ratio(between 5:1 and 20:1) of helium and neon at a total pressure of about 1 torr inside of a small electrical discharge. ![]()
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