The term electro-optics is used with substantially different meanings, which are explained in the following sections.
Devices Based on the Electro-optic Effect
Electro-optics in a narrow sense is the field of science and technology around the electro-optic effect, i.e., the phenomenon that the refractive index of a material can be modified with an electric field. The most important kind of electro-optic devices is the electro-optic modulator, containing a Pockels cell as its core element. Besides, the electro-optic effect can also be utilized in the form of electro-optic sampling.
A broader understanding of the term electro-optics also includes other devices where optical propagation depends on electric fields – for example, electroabsorption modulators. Next, one may include devices where light causes electrical effects. Electro-optics is then essentially the same as optoelectronics. That can be considered as the technology of electronic devices that interact with light, or essentially the technology where both optics and electronics are involved. This field includes many more devices, such as for example photodetectors, laser diodes and photonic integrated circuits.
Sometimes, the term is understood to be even much broader, meaning essentially the same as photonics.