What does the term "quantum efficiency" refer to in photodetectors?

The term "quantum efficiency" in photodetectors specifically refers to the measure of how effectively a photodetector converts incident photons into an electrical charge. This is quantified as the ratio of the number of charge carriers (like electrons) generated in response to incoming photons to the total number of photons that hit the detector.

When a photon strikes the photodetector, it can result in the generation of an electron through processes such as the photoelectric effect. Quantum efficiency gives insights into how many of those incoming photons actually contribute to the generation of electrical signal, making it a crucial parameter in determining the photodetector's sensitivity and performance. A higher quantum efficiency indicates that the device is more effective in converting light into an electrical signal, which is particularly important in applications such as communications, imaging, and sensing.

The other options focus on different characteristics of photodetectors: energy efficiency pertains to the overall power consumption; durability refers to the lifespan and robustness of the device; and response speed relates to how quickly the photodetector can respond to changes in light intensity. None of these directly describe the specific process of photon-to-electron conversion that is central to understanding quantum efficiency.