Definition of laser

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Photonics Dictionary

laser: A laser, which stands for "light amplification by stimulated emission of radiation," is a device that produces coherent and focused beams of light through the process of optical amplification based on the principles of quantum mechanics.

Key features of lasers include:

Stimulated emission: The operation of a laser is based on stimulated emission, a quantum phenomenon where atoms or molecules in an excited state release photons when they encounter other photons. This process leads to the amplification of light.

Active medium: A laser contains an active medium, which can be a gas, liquid, or solid material. The active medium consists of atoms or molecules that can be excited to higher energy states and then emit photons as they return to lower energy states.

Energy source: An external energy source, such as an electrical discharge or another light source, is used to pump energy into the active medium and create a population inversion, where more atoms or molecules are in an excited state than in a lower energy state.

Optical cavity: The laser system typically includes an optical cavity, formed by two mirrors facing each other. One of the mirrors is highly reflective, while the other is partially transparent. The cavity helps in the feedback and amplification of the light.

Coherence: Laser light is characterized by coherence, meaning that the light waves have a consistent phase relationship. This coherence allows laser light to be focused into a narrow beam, maintaining its intensity over long distances.

Monochromaticity: Laser light is often monochromatic, meaning it consists of a single color or wavelength. This property is a result of the specific energy transitions in the active medium.

Applications: Lasers have a wide range of applications across various fields, including communications, medical procedures, manufacturing, scientific research, and entertainment. They are used in devices such as laser pointers, laser printers, surgical lasers, and in technologies like fiber optics.

The invention of the laser is attributed to physicist Theodore H. Maiman, who built the first functional laser in 1960. Since then, lasers have become an essential and ubiquitous technology, contributing significantly to diverse areas of science and industry.