Optoelectronics, in the context of science, deals with light, its detection, creation and manipulation for various purposes. This includes X-rays, gamma rays, infrared, ultraviolet and of course visible light. These devices are basically transducers, devices that convert one form of energy into another form of energy, and can either be electrical-to-optical, which usually means that the machine produces light by expending or using electrical energy, or they can be optical-to-electronic, which means that the device is a detector of light and transforms the detected light signals into equivalent electrical signals for computer processing.

Optoelectronics use the quantum mechanical effect of light on materials used in electronic devices such as semiconductors. These effects are:

• Photovoltaic or photoelectric — This is the direct conversion of light into electricity, which is the effect taken advantage of by solar cells.
• Photoconductivity — This is an electrical phenomenon wherein a material becomes more conductive to electricity through the absorption of electromagnetic radiation such as infrared, ultraviolet and visible light. It is used in charge-coupled device (CCD) imaging sensors.
• Stimulated emission — This is a process where a light photon interacts with an excited molecule which causes it to drop to a lower energy level, resulting in the emission or "liberation" of an identical photon which is transferred to the electromagnetic field. This process is used in laser diodes and quantum cascade lasers.
• Radiative recombination — Electrons are transitioned from the valence to the conducting band in semiconductors, resulting in a carrier generation and recombination effect which produces light. This process is how LEDs produce light.

Optoelectronics should not be confused with electro-optics, as this field is a wider branch of physics that deals with the interaction of electric fields and light, without concern if an electronic device is involved or not.