Define 'quantum efficiency' in the context of photodetection.

Quantum efficiency is a critical parameter in the field of photodetection, as it quantifies how effectively a photodetector converts incoming photons into usable electrical signals. The correct definition of quantum efficiency is the ratio of the number of charge carriers generated—such as electrons in a semiconductor—to the number of incident photons that strike the detector. This ratio provides insight into the effectiveness of the photodetector in converting light into an electrical signal, with a higher quantum efficiency indicating better performance.

In practical terms, a photodetector with high quantum efficiency means that a significant portion of the incident photons results in the generation of charge carriers, which can then be measured as an electrical signal. This is essential for applications like imaging, spectroscopy, and optical communication, where maximizing signal detection and minimizing noise are crucial.

While other definitions like the speed of detection or total energy output may relate to photodetector performance, they do not specifically address how well photosensitive materials convert light into electrical signals, thus not accurately defining quantum efficiency. Similarly, while the percentage of absorbed photons creating charges is a relevant concept, it does not fully encompass the ratio aspect defined by quantum efficiency, which includes all incident photons, not only those absorbed.