A solid-state laser is a type of laser that uses a solid gain medium (as opposed to a liquid or gas) to produce coherent light. The term "solid-state" refers to the fact that the active medium, where the lasing action occurs, is a solid material. This material is typically a crystalline or glass-like substance doped with specific ions or atoms that can undergo stimulated emission to generate laser light.
The basic components of a solid-state laser include:
Gain medium: This is the solid material that amplifies light through the process of stimulated emission. Common materials include crystals such as ruby (chromium-doped aluminum oxide), neodymium-doped yttrium aluminum garnet (Nd:YAG), or other rare-earth-doped crystals.
Pump source: Solid-state lasers require an external energy source to "pump" or excite the atoms or ions within the gain medium to higher energy levels. This energy source is typically a flash lamp or a diode laser.
Cavity or resonator: The laser cavity or resonator is a set of mirrors that forms an optical cavity within the gain medium. One of the mirrors is highly reflective, while the other is partially transparent, allowing the emitted laser light to exit the cavity.
Output coupler: The partially transparent mirror in the cavity, known as the output coupler, allows a portion of the generated laser light to exit the cavity as the useful output beam.
When the gain medium is pumped with energy, it can reach a population inversion state, where more atoms or ions are in higher energy states than lower ones. Stimulated emission then occurs, leading to the emission of coherent light. The cavity and mirrors help to amplify and maintain the coherence of the emitted light, resulting in a well-defined and focused laser beam.
Solid-state lasers find applications in various fields, including materials processing, medical procedures, communication, and scientific research. Their solid-state nature provides advantages such as compactness, durability, and efficiency.