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Photonic Crystal Laser Diodes
Published in Joachim Piprek, Handbook of Optoelectronic Device Modeling and Simulation, 2017
Photonic crystals are periodic structures designed to affect electromagnetic waves in a similar manner to how solid-state crystals affect electrons. The simplest, one-dimensional form of a photonic crystal is a periodic multilayer film (Bragg mirror). Such films were already being studied 120 years ago, in 1887, by Rayleigh [1]. They continued to be the subject of intensive research, resulting in the development of thin-film optics: the science and technology of fabricating dielectric multilayer mirrors, filters, polarizers, antireflection coatings, and so on. However, it took a whole century before the technology was expanded into two and three dimensions by Yablonovitch [2] and John [3] in 1987. Since then, the term photonic crystal has become widely used and the subject is studied all over the world.
Basic Theory
Published in H. Angus Macleod, Thin-Film Optical Filters, 2017
The change in phase produced by a traversal of distance z in the medium is the same as that produced by a distance nz in a vacuum. Because of this, nz is known as the optical distance, as distinct from the physical or geometrical distance. Generally, in thin-film optics, one is more interested in optical distances and optical thicknesses than in physical ones.
Past, present, and the future of the research and commercialization of CVD diamond in China
Published in Functional Diamond, 2022
Diamond thin film coated optical windows can be used in extremely hostile environment (high temperature, highly erosive, corrosive, or radiative environments) where other substrate window materials could not withstand. The transmission of the diamond thin film coated window depends not only on the optical quality of the thin diamond film and the substrate, but also to a greater importance on the surface roughness Ra and thickness of the thin film coating, and should be calculated by the theory of the thin film optics [70]. Besides, adhesion of the thin diamond film coating on the substrate surface is of vital importance, but unfortunately, due to the very low thermal expansion coefficient of the diamond, the adhesion is usually poor. And a buffer layer is usually needed. Typical example is the R&D of the diamond thin film coated ZnS windows which were of great concern both in and outside of China [71–73]. However, due the extreme difficulties encountered, it was not successful. Nevertheless, there were a few successful cases reported for other substrate materials [69, 74]. The needs for diamond thin film coated optical windows is apparent while the market is rather small.