Helium-Neon Laser
The first He-Ne laser was fabricated in 1961 by Ali Javan, Bennett, and Herriott at Bell Telephone Laboratories. others. Helium-Neon laser is a gas laser. In this a mixture of helium and neon gas plays an important role in gain medium. We can write Helium-Neon laser as He-Ne laser. The helium-neon laser was the first continuous-wave laser. The He-Ne laser operates at a wavelength of 632.8 nanometres (nm), in the red portion of the visible spectrum.
Ruby laser is a pulse laser, even though it has a high intense output. Use of gas lasers is to obtain continuous laser beams. However using gas lasers, we can achieve high coherence, high directionality, and high monochromaticity beam. The output power of the gas laser is generally in a few milliwatts.
Construction of Helium-Neon Laser
The helium-neon laser made up of three essential components:
- Pump source (high voltage power supply)
- Gain medium ( discharge glass tube or laser glass tube)
- Resonating cavity
Pump Source
The gain medium of a He-Ne laser made up of a mixture of helium and neon gas contained in a glass tube at low pressure. Also In the He-Ne gas laser, the He and Ne gases are taken in the ratio 10:1 in the discharge tube.
Gain Medium
In general discharge tube’s length is 80cm and diameter is 1cm. The output power of these lasers depends on the length of the discharge tube and the pressure of the gas mixture. Therefore, to achieve population inversion, we need to pump electrons from the lower energy state of the helium. In He-Ne laser, neon atoms are the active centers and have energy levels suitable for laser transitions while helium atoms help in exciting neon atoms.
Resonating Cavity
Two reflecting mirrors are fixed on either end of the discharge tube. Out of which one mirror is partially reflecting and the other mirror is fully reflecting. The fully silvered mirror will completely reflect the light whereas the partially silvered mirror will reflect most of the light but allows some part of the light to produce the laser beam.
Advantages of He-Ne Laser
- The He-Ne laser emits laser light in the visible portion of the spectrum.
- High stability and low cost
- Operates without damage at higher temperatures
Disadvantages of He-Ne Laser
- It has Low efficiency and Low gain.also limited to perform low power tasks.
Application of Helium-Neon Laser
- Helium-neon lasers also have applications in the industries, scientific instruments and also in college laboratories.
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