Which of the following statements about lasers is true?

The statement that lasers can produce both spontaneous and stimulated emission is accurate and highlights a fundamental characteristic of laser operation. In the context of lasers, spontaneous emission refers to the process by which electrons in a material transition from a higher energy state to a lower energy state, releasing a photon without external influence. This phenomenon does occur in lasers and is critical in the initial stages of laser action.

However, the essential feature of laser operation is the stimulated emission process. In stimulated emission, an incoming photon stimulates an excited electron to drop to a lower energy state, resulting in the release of a second photon that is coherent with the first, meaning it has the same phase, frequency, and direction. This coherent light is what defines laser output and differentiates it from other light sources.

A truly distinguishing aspect of lasers is that they primarily depend on stimulated emission to produce the high-intensity, coherent light for which they are known. The combination of both spontaneous and stimulated emission contributes to the overall functioning of lasers, particularly during the startup phase, but it’s the stimulated emission that dominates the output once the laser is operational.

In summary, the ability of lasers to utilize both types of emission is critical to understanding how they generate light, particularly the coherent and monochromatic nature that