The chapter titled, “Optical and Photonic Applications,” describes the numerous and vital functions that thin films play in the domains of optics and photonics. In this chapter, various uses of thin films including antireflection coatings, optical filters, mirrors, and photovoltaics are explained. Reflective coatings are necessary mostly antireflective to reduce the amount of light that is reflected back by the optical surface and increase the amount that is transmitted through lenses and other optical parts. Multilayer thin films used in optical filters permit or reject certain wavelengths of light which is vital in imaging as well as telecommunication. Moreover, the chapter explores the application of thin films in the construction of mirrors especially in delivering high reflectivity and at the same time improving their life span. Thin films are used in photovoltaics to produce high-performing solar cells by changing sunlight into electricity in a more efficient and economical way. In this chapter, the authors illustrate detailed descriptions of these applications which unveiled the role of thin film as a central factor in the progression of the optical and photonic elements, stimulating advancement and enhanced performance in numerous devices and systems. The discussed information provides a deep insight into the possibilities of thin-film applications in modern optical and photonic engineering.