Detection of Energetic Ions Based on Tapered Optical Fiber

Single-mode tapered optical fibers (TOF) are well-known for applications in sensing. In this work, we demonstrate the use of tapered optical fibers to detect charged particles (ions) irradiated at various energies, fluences, and species. In this experiment, two different ion species, namely, Ar+ and N+, have been used to irradiate tapered optical fibers at various fluences and energies. The variations in the free spectral range (FSR), period, and transmission power loss from the ion beam irradiated TOFs are picked up by the optical spectrum analyzer (OSA). We were able to identify ions with energy as low as 80 keV because of the change in the refractive index of the cladding material caused by the implanted ions. The observed changes in spectra are explained using the results of COMSOL simulations. Using Monte Carlo-based TRI3DYN ion-solid interaction simulation, the surface modification and defect formation caused by ion beams as well as the implantation profile in the TOF have been predicted. These results are further corroborated by experimental studies such as scanning electron microscopy and Raman scattering spectroscopy. Such a tapered optical fiber-based detection method will aid in the creation of portable equipment to identify charged particles in nuclear reactors and in space exploration.