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DataRay Inc. - ISO 11146-Compliant Laser Beam Profilers
Photonics Dictionary

active medium

An active medium is a material or substance used in various optical devices and systems, where it plays a critical role in amplifying light or producing laser beams through the process of stimulated emission. The active medium can be found in lasers, amplifiers, and other photonic devices.

Lasers: The active medium in a laser is the material that, when excited by an external energy source (such as electrical current, light, or chemical reaction), emits photons through the process of stimulated emission. This medium can be a gas (e.g., CO2 laser), a liquid (e.g., dye laser), a solid (e.g., ruby laser), or a semiconductor (e.g., diode laser). The active medium determines the wavelength and properties of the laser light.

Optical amplifiers:
In optical amplifiers, the active medium is the substance that amplifies an incoming light signal. For example, in an erbium-doped fiber amplifier (EDFA), the active medium is an optical fiber doped with erbium ions. When pumped with light at specific wavelengths, the erbium ions amplify the signal passing through the fiber.

Plasma physics:
In plasma physics, the active medium can refer to the ionized gas that, when excited, emits light or radiation. This principle is utilized in devices like plasma displays and certain types of gas discharge lamps.

The active medium is crucial for the operation of these devices, as it directly affects the efficiency, output power, and spectral properties of the emitted light or radiation.
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