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HeNe Laser

Introduction

In this type of laser, the active medium consists exclusively of neutral atoms in the gaseous state. The best example is the helium-neon laser (HeNe), known for the purity of its wavelength emission and directivity of the beam produced. It was the first gas laser constructed. It has a small output power and is inexpensive to produce. For these reasons it is used for patient positioning for radiographs, for reading bar codes or optical experiments. In this laser, helium is excited by the electric discharge. These atoms are then exciting the neon atoms by collision. Finally, neon emits light. The HeNe laser is used particularly for its red emission at 632.8 nm, although it emits a few other wavelengths (Kasap, pp.113-176).

HeNe laser tube in operation, the pink light is not laser emission but rather the light emitted by fluorescence helium.

Discussion

Helium-neon laser - along with the diode or semiconductor is among the most frequently used and most affordable lasers in the visible spectral region. Power laser systems of this kind, intended primarily for commercial purposes, is in the range from 1 mW to several tens of mW. Especially, He-Ne-laser of 1 mW popular is not so powerful, which is used mainly as quotation devices, as well as for solving other problems in the field of measurement technology. In the infrared and red bands of helium-neon laser is increasingly replaced by a diode laser. He-Ne-lasers are capable of, along with the red lines radiate as orange, yellow and green, which is achieved through appropriate selective mirrors (John & Wiley pp. 119-205).

The Operation of HeNe Laser

The most important function for the He-Ne-laser energy levels of helium and neon .Laser transitions occur in an atom of neon, with the most intense lines are due to transitions with wavelengths 633, 1153 and 3391. The electronic configuration of neon in the ground state is as follows: 1 s 2 2 s 2 2 p 6 and the first shell (n = 1) and the second shell (n = 2), respectively, are filled with two or eight electrons. Higher states of result has been obtained from the fact that there is a 1 s 2 2 s 2 2 p 5-shell and glowing (optical) electron is excited according to the scheme: 3 s, 4 s, 5 s, ..., N p, 4 p, ... etc. It is, therefore, on the one-electron state, carrying out communication with the shell. In the scheme of LS (Russell - Saunders) for the energy levels of neon indicated one-electron state (e.g., 5 s), as well as the resulting total orbital angular momentum L (= S, P, D.) (Hecht, pp. 101-119). In the notation S, P, D, subscript indicates total orbital angular momentum J, and the top - the multiplicity 2S + 1, for example, 5 s 1 P 1. Often used purely for phenomenological designation of Paschen. At the same time due to the sublevels of excited electronic states is 2 to 5 (for s-states) and ...