What is the fundamental mechanism of a diode laser?

The fundamental mechanism of a diode laser is based on the semiconductor junction. In a diode laser, a p-n junction is formed by joining p-type and n-type semiconductor materials. When a voltage is applied across the junction, electrons from the n-type region move toward the p-type region, and holes from the p-type region move toward the n-type region. This movement of charge carriers leads to recombination, where electrons fill holes, releasing energy in the form of photons—this process is known as spontaneous emission.

Once a critical number of photons is produced, they stimulate further electron-hole recombination, resulting in a chain reaction of stimulated emission. This is what produces the coherent light that characterizes laser operation. The carefully designed structure of the semiconductor and the properties of the materials used enhance this process, allowing for efficient light emission.

Other mechanisms, such as thermal excitation, photoelectric effect, and quantum tunneling, play roles in different physical contexts but are not the primary processes that underpin how a diode laser operates. In particular, thermal excitation relates to solid-state physics phenomena, the photoelectric effect involves light interacting with materials to release electrons, and quantum tunneling is a quantum mechanical phenomenon where particles pass through barriers. While these concepts are important in the field