What is the main component of a laser?

The main component of a laser is the gain medium. The gain medium is crucial as it is the material that amplifies light through the process of stimulated emission. When energy is supplied to the gain medium, typically through a power source, it excites the atoms or molecules within the medium. As these excited particles return to their ground state, they release photons, which can stimulate further emissions in a cascading effect, thus producing coherent light.

This amplification process relies heavily on the properties of the gain medium, whether it be a solid, liquid, or gas. The specific nature of the gain medium determines a laser's wavelength and functionality, which is why it plays such a pivotal role in laser operation.

While other components like the power supply provide the necessary energy, or optical lenses help focus the emitted light, it is the gain medium that fundamentally enables the production of laser light through amplification.