Lasermedia

Lasermedia, or laser medium, is the active material in a laser that provides optical gain through stimulated emission. The medium's electronic or vibrational energy levels determine the wavelength of light that can be amplified, as well as the efficiency and power handling of the device.

Common categories include solid-state media such as doped crystals and glasses (for example Nd:YAG, Er:YAG, or Ti:sapphire), liquid dye solutions, gaseous media (including carbon dioxide, helium-neon, and nitrogen lasers), and semiconductor media used in diode lasers. Fiber lasers employ doped optical fibers (such as Yb-doped silica) to achieve amplification within a fiber geometry.

Lasers operate by creating a population inversion in the medium, typically through pumping with optical, electrical, or chemical energy. The inverted medium amplifies light via stimulated emission as it passes through an optical cavity formed by mirrors. The choice of medium fixes the emission wavelength, gain spectrum, bandwidth, and thermal behavior.

Key performance properties include the gain coefficient, threshold pump power, saturation, bandwidth, and damage threshold. Practical considerations include thermal management, photodegradation (notably in dye lasers), lifetime of active ions, and mechanical or optical stability of the cavity.

Laser media have broad applications in industry, medicine, research, and communications, ranging from precision cutting and micromachining to spectroscopy, medical surgery, and LIDAR. Developments in media and pumping schemes continue to expand tunability, efficiency, and cost-effectiveness of laser systems.