Gas laser

A gas laser is a device that produces coherent light through an electric discharge. This process involves passing an electric current through a gas to create a concentrated beam. The gas laser was a major milestone in physics. It was the first laser capable of producing continuous light. It was also the first device to convert electrical energy directly into laser light output. These lasers are highly valued because they use a large volume of active material. This material is relatively inexpensive to obtain. Additionally, the active material is almost impossible to damage. The design also allows heat to be removed quickly from the cavity.

The mechanism of a gas laser relies on changing the energy of molecules. In these systems, gas molecules are cycled from a low energy state to a high energy state. This movement of energy is what creates the laser beam. This process is different from other lasers that cycle an electron inside an atom. By moving molecules through these energy levels, the device can produce a steady stream of light.

History shows that the first gas laser was the helium–neon laser, or HeNe laser. This device was co-invented in 1960 by Ali Javan and William R. Bennett, Jr. Javan was an Iranian engineer and scientist. Bennett was an American physicist. Their original HeNe laser produced light in the infrared region of the spectrum. This light had a wavelength of 1.15 micrometres. Today, many HeNe lasers operate at 633 nm. These are very common in schools and laboratories. They are popular because they are low in cost and have near-perfect beam qualities.

Scientists have developed many distinct types of gas lasers for different tasks. Carbon dioxide lasers, or CO2 lasers, are extremely powerful. They can emit hundreds of kilowatts of energy at wavelengths of 9.6 μm and 10.6 μm. These are often used in industry for welding and cutting materials. Another type is the nitrogen laser. These use molecular nitrogen as a gain medium to operate in the ultraviolet range. They typically produce light at 337.1 nm. There are also TEA lasers, which stands for Transversely Excited Atmospheric. These use a gas mixture at or above atmospheric pressure and are energized by high voltage.

Some lasers use chemical reactions instead of electricity for power. These are known as chemical lasers. They can release a large amount of energy very quickly. This makes them very powerful and useful for military applications. For example, George C. Pimentel invented hydrogen fluoride and deuterium fluoride lasers. These lasers create light by combining hydrogen or deuterium gas with ethylene combustion products in nitrogen trifluoride. Another specialized type is the excimer laser. These are powered by a reaction involving an excited dimer, or excimer. An excimer is a short-lived molecule formed from two species where at least one is in an excited electronic state. Excimer lasers produce ultraviolet light and are used in LASIK eye surgery and semiconductor photolithography.

Other specialized categories include ion lasers and metal-vapor lasers. Argon-ion lasers emit light between 351 and 528.7 nm. Common lines for these lasers include 458 nm, 488 nm, and 514.5 nm. Metal-vapor lasers also typically generate ultraviolet wavelengths. Examples include helium-silver, neon-copper, and helium-cadmium lasers. These are useful because they have very narrow oscillation linewidths. The copper vapor laser is notable for being the most powerful and efficient laser in the visible spectrum. It produces two spectral lines of green and yellow light.

The applications for these technologies are vast and varied. HeNe lasers are used to make holograms and were once used to read barcodes in stores. While laser diodes have largely replaced them for barcodes, HeNe lasers are still used to write on photosensitive material in laser printing. Different lasers also serve as pumps for other systems. Nitrogen and excimer lasers are used in pulsed dye laser pumping. Argon-ion lasers are used for continuous-wave dye laser pumping. From industrial cutting to delicate eye surgery, the gas laser remains a fundamental tool in modern science and industry.