Design of optical and microwave devices for iot applications and future telecommunications

This PhD thesis is focused on the design, optimization, and characterization of innovative optical and microwave devices supporting the development of the Sixth Generation (6G) of telecommunications and Internet of Things (IoT) applications. The need for high-speed communication and advanced sensing promotes the design of novel microwave and optical devices. The current research addresses these challenges through two distinct approaches: high-frequency devices, useful for Fiber-Wireless (FiWi) networks, and for beam-steering applications, where the antenna design and the improvement of radiative parameters can be achieved by employing Metamaterials (MTMs) and Metasurfaces (MTSs); and optical devices operating in the Mid-InfraRed (Mid-IR) range, targeting sensing or novel communication applications relevant to IoT and 6G. In particular, the Ph.D. thesis reports the following key contributions: 𝑖) the design and optimization of a Mid-IR Fiber Laser based on praseodymium-doped fluoroindate (Pr3+:InF3) glasses operating at 𝜆𝑠=4 𝜇𝑚; ii) the design and optimization of a Mid-IR Optical Fiber Amplifier based on praseodymium-doped fluoroindate (Pr3+:InF3) glasses operating at 𝜆𝑠=4 𝜇𝑚; 𝑖𝑖𝑖) the design, fabrication, and characterization of a non-adiabatic tapered ZBLAN optical fiber sensor operating in the Mid-IR range for temperature measurements; 𝑖𝑣) the design, fabrication and characterization of an Antipodal Vivaldi Antenna (AVA) with MTS; 𝑣) the design, fabrication and characterization of a Fabry-Perot Antenna (FPA) realized through unconventional fabrication techniques based on inkjet and 3D printing; 𝑣𝑖) the design, fabrication, and characterization of a Transmitarray Antenna (TA) for beam-steering applications and 𝑣𝑖𝑖) the design and optimization of a Folded Transmitarray Antenna (FTA) working in the millimeter-wave range. The last activity has been carried out in collaboration with the Institut d'Electronique et des Technologies du numéRique (IETR) of Rennes (France). Part of this research has been published in international journals and presented at national and international conferences, as detailed in the list at the end of the thesis.