Helium Neon Laser
While the helium neon laser is not the most efficient or powerful gas laser available, it does have some distinct advantages. Besides being able to emit visible light, it it affordable, provides thousands of hours of work, and has good beam quality. The gain medium is a mix of helium and neon gases in a 5 to 20:1 ratio. One of the most popular applications is non-contact measuring and monitoring. In surveying, the helium neon laser takes accurate and straight measurements over long distances and helps align high-power lasers and other cutting tools. In labs, it is part of optics demonstrations and is also used in holography, irrigation, parts detection and barcode scanning.
Helium neon lasers emit light at 632.8nm. They do not require any consumables or cooling devices because they don't generate high heat and are therefore comparably safer to use around people. While their natural visible color is red, florescent dies allow the laser to become a wide spectrum of colors, including orange, green and blue. The laser is made of 3 different components: the laser tube, a high voltage power supply and structural packaging. The tube is made of glass, and inside it contains the laser gas (helium and neon), electrodes, which discharge electricity through gas, and mirrors at the bottom, which increase efficiency. These tubes range in size anywhere from a couple centimeters to several meters in diameter. In the laser tube, the electrodes discharge electrons, transferring them to the gas atoms. There, spontaneous emission takes place, where the excited atom emits a photon and stimulates another atom to emit a photon. The helium atoms are there to keep energizing the neon, ensuring they have enough energy to transfer it. The energy that the atoms emit in the form of radiation can be focused into a beam of light by transmitting through the somewhat transparent mirrors.
