Which of the following devices is commonly associated with opto-electronics?

Photodetectors are devices specifically designed to sense and convert light into an electrical signal, which makes them a fundamental component of opto-electronics. These devices play a crucial role in applications like communication systems, imaging sensors, and optical instruments. They operate by detecting photons, utilizing semiconductor materials that generate charge carriers in response to light exposure, effectively bridging the fields of optics and electronics.

Transistors, while essential in electronics for signal amplification and switching, do not inherently involve the process of light detection or conversion, which is central to opto-electronic devices. Similarly, resistors and capacitors are passive electronic components that manage electrical energy without any interaction with optical signals. Therefore, photodetectors stand out as the correct choice due to their intrinsic link with light and the pivotal role they play in opto-electronic systems.