What are the two primary light emission processes in lasers?

The two primary light emission processes in lasers are stimulated emission and spontaneous emission.

Stimulated emission is the fundamental process that allows lasers to produce coherent light. In this process, an incoming photon stimulates an excited atom or molecule to release a photon of the same energy, phase, and direction as the incoming photon. This creates a chain reaction, where one photon stimulates the emission of more photons, leading to an amplified light output that is characteristic of laser operation.

Spontaneous emission, on the other hand, occurs naturally when an excited atom or molecule returns to a lower energy state without any external influence, resulting in the emission of a photon. While spontaneous emission can contribute to the overall output of a laser, it is primarily through the process of stimulated emission that lasers achieve their unique properties of coherence, monochromaticity, and directionality.

The other options do not accurately describe the primary processes involved in laser light emission. Single emission and double emission do not represent recognized mechanisms in laser physics. Continuous emission and pulsed emission refer to the modes of operation of a laser rather than the fundamental processes of light emission. Lastly, active emission and passive emission are terms related to different systems in optics but do not encapsulate the two essential phenomena leading to laser action.