Recent progress in germanium-core optical fibers for mid-infrared optics

The search for low-loss and robust optical fibers in the infrared spectrum has always been an important research topic for many investigators. Over the years, fibers of various materials groups have been proposed to obtain ‘the ultimate infrared fiber’. Recently, a new competitive alternative has emerged: the semiconductor-core glass-cladded optical fibers. The excellent bulk materials properties and integrated circuit applications reveals the potential of semiconductors as fiber materials. One of the important photonic materials that has been proposed as a fiber-core material is germanium. In this paper, the development of Ge-based fibers and their optical properties in the mid-infrared spectrum are discussed. The performance of Ge-based fibers has been compared with other semiconductor-core fibers. Recent developments in the area of semiconductor fibers and the future prospects of semiconductors as infrared fiber materials are also discussed.