The gain medium is the core material in a laser that amplifies light through stimulated emission. It can be a gas, liquid, solid, or semiconductor, and is chosen based on the desired wavelength and application.
Key Roles of the Gain Medium:
- Light amplification: When a photon of the right energy passes through the gain medium, it can trigger stimulated emission from excited atoms, releasing identical photons.
- Population inversion support: The medium must be pumped (optically, electrically, or chemically) to maintain more excited atoms than ground-state atoms.
- Determines laser properties: The wavelength, efficiency, and power of the laser are strongly influenced by the choice of gain medium.
In essence, the gain medium enables the cascade of coherent photons that defines laser operation.