Avalanche Photodiode Diffraction Structure for Small-Pixel Photon Detection

The patent introduces a temporal dimension to light-photon interaction by implementing a photon recycling mechanism. Photons that initially miss the active avalanche initiation region are reflected back by a diffraction grating structure, giving them multiple opportunities to be detected. This transforms a spatial limitation into a temporal process where undetected photons are redirected and re-attempted, effectively increasing detection probability without increasing pixel size.

The diffraction grating structure acts as an intermediary element between incident photons and the photodiode. This intermediary redirects photons that would otherwise be lost, channeling them back into the active region. The grating serves as a mediating structure that resolves the contradiction by providing an additional pathway for photon detection without requiring larger pixel dimensions.

The patent implements continuous useful action through photon recycling. Instead of a single-pass detection model, the system continuously redirects undetected photons back into the active region through the diffraction grating. This creates a continuous detection process where photons multiple times interact with the active region until detected, maintaining high absorption efficiency even in small pixels.

The patent converts the harmful effect of photons missing the active region into a beneficial recycling opportunity. Rather than losing photons that miss the small active region, the diffraction grating reflects these photons back, transforming what would be energy loss into additional detection opportunities. This converts the harm of small pixel size into a benefit through systematic photon redirection.