What is the difference between optics and optics?

This is a very good question. Optical optics was used earlier, and people's understanding of optics began from the level of geometric optics, and later developed into wave optics that explained optical phenomena with electromagnetic field theory. This is what we often call optics, optics. With the development of science and technology, the veil of molecules, atoms and electrons has been unveiled one by one. People's understanding of optics has also improved to the photon level, photonics, photonics, optoelectronics and so on. Have also appeared, all from the study of photonics. Therefore, it can be understood that optics refers to optics in general, while phototics focuses on optics understood from the perspective of photons.