اللايزر - الضوء .. الفيزياء

Laser - Light .. Physics

Laser

The process of emitting a photon from an excited atom or an excited molecule is characterized by being difficult to control, and that the emission sometimes contains photons that do not have the same frequency and are launched in all directions. Einstein had predicted in 1917 that stimulating the emission (or urging it) by the interaction of the atom with a photon that comes to it carrying the appropriate energy is very possible, and that using this stimulated emission requires the presence of a large number of electrons at a very high energy level. This condition, called the census reflection, can be achieved by pumping energy into the device used. If the atom has two high energy levels, it is stimulated by photons emitted from light electromagnetic rays that transfer electrons from their higher level to their lower level Q2.

These photons have an energy level equal to the difference Q1 - Q2. After that, the photons resulting from the emission number process are launched in a direction close to the direction of the stimulated rays and their frequency becomes equal to the resultant (Q1 - Q2) / h. Then the emitted photons in turn stimulate a new emission that leads to the generation of a narrow beam of amplified rays of a single color (single frequency) and with a high energy density per unit area. In general, stimulated emission is characterized by being coherent rays (in phase), unlike spontaneous emission, which is characterized by its lack of coherence at all.

(Sapphire laser)
(Helium and neon gas laser)

Stimulated emission is used in lasers to amplify light, ultraviolet rays, and infrared rays. The existing laser devices are divided into three types: solid-state lasers, gas lasers, and semiconductor lasers. In the ruby ​​laser, chromium ions are prepared as impurities in aluminum oxide, and they emit photons that have been previously excited by a strong glow of light. The wavelength of the stimulated rays is 694.3 nanometers and they are sent in the form of pulses. As for the gas laser, the gas is excited at low pressure by continuous electric discharges. It is known that the laser that works with a mixture of helium and neon gases gives continuous light with a wavelength of 634.2 nanometers. As for the laser that works with carbon dioxide, it gives a light beam with a wavelength of 6.10 micrometers and is characterized by being much stronger than infrared rays.

Laser rays are made to oscillate between two times - one reflective and the other semi-reflective located at the ends of the device, and a distance equal to n l / 2 separates them, where n represents an integer and l represents the wavelength.

This wave is designed to oscillate only or to perform a response action. The device itself is called the responsive chamber. The beam of rays is then amplified by additional stimulated emission resulting from the use of a number of reflections. After that, a beam of rays with a very large power emerges from the semi-reflective mirror.