What component of the laser acts as the feedback mechanism for light amplification?

The optical cavity is a crucial component of a laser that serves as the feedback mechanism for light amplification. It consists of two mirrors positioned at each end of the cavity—it reflects photons back and forth, allowing them to stimulate further emissions of light from the excited atoms or molecules within the gain medium. This process enhances the intensity of the light through stimulated emission, contributing to the coherent beam characteristic of lasers.

The design of the optical cavity is essential because it not only facilitates the amplification of light but also determines the characteristics of the laser output, such as its wavelength. The mirrors must be highly reflective to maximize feedback and photon recycling, while one mirror is partially transmissive to allow some of the amplified light to escape as the laser output.

In contrast, the other components mentioned have different roles in the laser's operation. The pump source provides the energy required to excite the atoms in the gain medium. The stimulus module is not a standard term used in laser technology, and the output coupler, while important for allowing some light to exit the cavity, does not function as a feedback mechanism itself; its primary role is to control the amount of light that emerges from the laser.