 Photonic sensors are essential in modern science and technology as they can detect changes in electromagnetic waves and convert them into an electric signal. Scientists have developed various types of photonic sensors, including optical waveguides, optical fibers, plasmonics, metasurfaces, and photonic crystals. Light is used to measure the transmission or reflection spectrum of these sensors, which are typically based on resonance cavities or greetings. This paper provides an overview of the different types of photonic sensors available, such as those based on optical waveguides, optical fibers, plasmonics, metasurfaces, and photonic crystals. This article was authored by Muhammad A. Butt, Nikolai L. Kazanski, Svelana N. Kanina, and others.