What process is responsible for the intensity of a laser?

The process responsible for the intensity of a laser is stimulated emission. In a laser, the generation of coherent light is primarily due to stimulated emission, where an incoming photon induces an excited atom or molecule to release a photon that is in phase with the incoming one. This results in the amplification of light, allowing the intensity of the laser to increase significantly.

When a photon interacts with an excited electron, it prompts the electron to drop to a lower energy state while emitting another photon. This newly emitted photon has the same energy, frequency, phase, and direction as the triggering photon, leading to a phenomenon called light amplification. Given that multiple photons can be produced in this manner, stimulated emission is essential for achieving and maintaining the high intensity characteristic of laser light.

The other processes mentioned have their own roles in the broader context of light behavior. For instance, spontaneous absorption involves an electron absorbing a photon without any influence from an existing photon field, leading to a less controlled process. Thermal radiation refers to the emission of energy due to temperature, which doesn't generate the coherent light required for laser operation. Photonic interference relates to the interaction of light waves, resulting in variations in intensity, but it is not responsible for the generation of the intense, coherent beam found in lasers