He-ne laser is one of the earliest, most mature and most widely used lasers. Gas atoms have a definite energy level structure and are excited by external electrons The energy level transition generates excited radiation to emit laser. Therefore, the wavelength of He-ne laser is pure monochromatic light with extremely narrow linewidth and wavelength error of only a few nanometers, which has great coherence length Degree. Some lasers that emit light by band transition, such as LD, have monochromatic and coherent properties that cannot be compared with them. The atomic level structure is determined, so the laser is not affected by temperature fluctuations. In addition, the resonator ensures that the laser output has good collimation, and the divergence Angle is only a few milliradians. In the need for good monochromatic light, coherence and collimation of the occasion, especially Especially in the field of precision measurement, gas laser has an unshakable position.

The main disadvantage of helium atmosphere laser is that it needs high voltage DC power supply, which requires higher technical content and higher cost compared with LD.