What Is a Gas Laser?

A gas laser uses a gas as a working substance to generate a laser. It consists of three main parts: an activating gas in a discharge tube, a resonant cavity formed by a pair of mirrors, and an excitation source (Figure 1). The main excitation methods are electric, pneumatic, optical and chemical. Among them, the electric excitation method is the most commonly used. Under proper discharge conditions, using electron collision excitation and energy transfer excitation, gas particles are selectively excited to a certain high energy level, thereby inverting the number of particles with a certain low energy level, resulting in stimulated emission transition.

This is a type of laser that uses gas as a working substance. The gas mentioned here can be pure gas or it can be

He-Ne lasers are among the earliest and most common gas lasers. It was invented in 1961 by Dr. Javan, an Iranian scholar who is engaged in research work at Bell Labs in the United States, and his colleagues. The working substance is a mixture of helium and neon gases in a certain proportion. Depending on the operating conditions, five different wavelengths of laser light can be output, and the most commonly used is red light with a wavelength of 632.8 nm.

A gas laser uses a gas as a working substance to generate a laser. It consists of

Compared with solids and liquids, the gas has good optical uniformity. Therefore, the output beam of a gas laser has better directivity, monochromaticity, and higher frequency stability. The density of the gas is small, and it is difficult to obtain a high concentration of excited particles. Therefore, the energy density output by a gas laser is generally smaller than that of a solid laser.

The gas laser has a simple structure, low cost, convenient operation, uniform working medium, good beam quality, and stable and continuous work for a long time. It is the most widely used laser, with a market share of 60%.

Gas lasers are divided into atomic gas lasers, ion gas lasers, molecular gas lasers, and excimer lasers. They operate over a wide range of wavelengths, from vacuum ultraviolet to far infrared, and can work in either a continuous or pulsed mode.

Atomic gas laser

Includes various inert gas lasers and various metal vapor lasers, such as helium-neon lasers and copper vapor lasers. Where the He-Ne laser is

Gas laser

The earliest studies were successful and are still in widespread use. Its working substance is neon mixed with helium (Figure 2). In this mixed gas discharge, part of the helium atoms are excited to the metastable excited state 21S or 23S. When this part of the helium atom collides with the ground-state neon atom, it can lead to energy transfer excitation, so that the neon atom is at the excitation energy level, so as to realize the distribution of the number of neon atom particles inversion. Neon atoms emit lasers at three wavelengths (3.39 micrometers, 1.15 micrometers, and 6328 angstroms) in a resonant cavity through stimulated emission processes. The laser power output from a He-Ne laser is only a few milliwatts to 100 milliwatts, and the efficiency is about 0.1%. However, helium-neon lasers have the advantages of good monochromaticity, strong directivity, easy to use, compact and rugged structure, etc., so they are widely used in precision measurement, collimation and ranging.

Gas laser

Copper vapor lasers have the advantages of high average power and high repetition rate, and have developed rapidly.

Gas laser ion gas laser

The particle number inversion is established between the electronic state energy levels of the ions of the inert gas and the metal vapor. The laser wavelength is mostly in the ultraviolet and visible light regions, and the output laser power is large. Typical ion lasers include argon ion lasers, krypton ion lasers, and helium cadmium lasers. The most widely used are argon ion lasers. It can produce lasers with multiple wavelengths, the strongest of which are 4480 angstroms and 5145 angstroms. The continuous output laser power is several hundred milliwatts to several hundred watts, and the efficiency is very low, about 0.1%. It is used in spectroscopy, optical pump dye lasers, laser chemistry, and medicine.

Gas laser molecular gas laser

The working substance is a neutral molecular gas, such as nitrogen, carbon monoxide, carbon dioxide, and water vapor. The wavelength range is wide, from vacuum ultraviolet, visible light to far infrared. Among them, the carbon dioxide laser is the most important, which is characterized by high efficiency, in the range of about 10% to 25%, high laser power can be obtained, continuous output power up to 10,000 watts, pulse device output up to 10,000 joules per pulse level. This laser operates on multiple molecular vibrational spectral lines centered at 9.4 microns and 10.4 microns. Carbon dioxide lasers are divided into ordinary low-pressure sealed-off lasers, lateral and longitudinal gas circulation flow lasers, lateral atmospheric and high-pressure continuous tuning lasers, pneumatic lasers, and waveguide lasers. These lasers can be used in processing and processing (such as welding, cutting and heat treatment), optical communications, ranging, isotope separation, and high-temperature plasma research. The waveguide CO2 laser is a compact, high-gain and tunable laser, which is particularly suitable for laser communication and high-resolution spectroscopy.

Gas laser excimer laser

Lasers that utilize stimulated emission between an excimer-bound high energy state and a repulsive or weakly-bound ground state. Due to the extremely short life of the ground state, high efficiency and high average power can be achieved. The main excimers of excimer lasers are inert gas excimers and inert gas halide excimers. The laser emission wavelength is mainly in the ultraviolet and vacuum ultraviolet regions, and the output energy has reached the order of hundred joules. It is used for optical pump dye lasers, isotope separation, and laser chemistry.