What are the advantages and disadvantages of helium-neon laser?

The He-Ne laser is one of the earliest, most mature, and most widely used laser devices. Its gain medium is a gaseous mixture of approximately a 10:1 ratio of helium and neon. In a gaseous mixture, helium atoms are excited from the ground state to higher energy levels, triggering stimulated emission of photons that allows photon emissions in the gain medium. A He-Ne laser device emits a monochromatic laser with a long coherence length, and the wavelength deviation can be controlled to several nanometers. The performance of a He-Ne laser device is independent of thermal fluctuation, and the presence of an optical cavity ensures collimation of the emitted laser beam (divergence angle is only a few milliradians). He-Ne laser is widely applied in industries where good monochromaticity, coherence, and collimation are required, especially in the manufacturing industry for precision measuring devices.

However, a direct high-voltage current is required for the power supply, increasing the device’s failure rate. Because of the consistency of the wavelength, the application area of the He-Ne laser is restricted. The wavelength of the He-Ne laser is larger than those of green and blue lasers, resulting in a low capability of measuring sub-micron particles. The service life of the He-Ne laser is much shorter than that of the semiconductor laser, and its usage is also limited by the large volume of the device.

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