Analysis of tapered optical fiber for filtering and mode transformation

Abstract

The rapid growth of information technology is closely tied to the advancement of modern telecommunication systems. Optical fiber communication has emerged as a crucial element, enabling high-speed and high-quality communication systems. Today, optical fibers are used not only for telecommunications connections, but also for the Internet and local area networks (LANs), achieving high transmission speeds. However, optical signals in optical fibers often require manipulations such as filtering and mode transformation for number of reasons such as Bandwidth management, integrating different fiber types, conditioning of signal, multiplexing, and demultiplexing etc. The proposed device utilizes a tapered optical fiber for filtering and mode transformation. This design consists of two stages, where the first stage involves a tapered optical fiber (𝑅=1μ𝑚, 𝑟=0.5μ𝑚, 𝐿=5μ𝑚) that achieves 0.83 normalized power and a half-power bandwidth (HPBW) of 0.17 μ𝑚 at a wavelength of 1.44 μ𝑚. The second stage extends the first stage by adding a metal layer over the optical fiber, enabling the conversion of photonic to plasmonic mode. At the metal fiber interface, the coupling efficiency reaches 81.2%, showcasing a clear preference for silver as the optimal metal choice. This preference is based on its ability to maximize power transmission compared to other metals. However, the thickness of metal layer does not contribute to the mode conversions. The proposed device demonstrates excellent suitability for performing various operations and holds great potential for applications in photonic devices at the nanoscale.