Comprehensive reading Gas and Molecular Lasers Gas Lasers

Gases offer interesting possibilities as laser materials because their atoms are more suitable for excitation. The neon lasers were the first to be discovered and studied and are the easiest to construct and to оperate. They use a mixture of helium and neon gases through which an electrical discharge flows, in the same way as in a conventional neon tube.

The discharge is provided by the radio-frequency generator which is usually operated in the 25-to-30 mс region. It serves to establish an electric discharge in the gas, although a d-c discharge may serve the purpose as well.

The energy from the internal discharge excites the helium atoms to a very high energy level, from which they normally would not radiate energy. However, the neon atoms in the mixture collide with the excited helium atoms, and the energy is transferred to them through the collision process. The neon atoms themselves can then be stimulated to radiate their energy in a continuous stream.

The beam is reflected back and forth through the length of gas-filled tube by semi-reflecting end plates, growing in intensity with each trip. Some part of the beam is transmitted through the plates, and forms a very narrow output beam of coherent infra-red light (Fig.1).

reflecting end plates