Single-crystal sapphire is an important material for optical sensing under high-temperature conditions. In this work, we investigate the effects of hydrogen ion implantation and post-implantation annealing on the structural and optical properties of sapphire crystals. Both c- and m-plane sapphire crystals were implanted with hydrogen ions of energy in keV-MeV to doses up to 1×10¹⁷/cm². Post-implantation annealing was conducted in the temperature range between 500 and 1500 ºC. The structural properties of these sapphire samples were characterized with a variety of analytic techniques, including nuclear reaction analysis for hydrogen profiling, Rutherford backscattering/ion channeling and x-ray diffraction for crystal quality, and Raman scattering for stresses retained in the sapphire crystal. In addition, the optical constants (e.g., refractive index and absorption coefficient) were determined using ellipsometry and prism coupling measurements. Based on the correlation of the structural and optical modifications in sapphire, we discuss the implication of using ion beams to fabricate optical waveguides in sapphire crystals for high-temperature sensing applications.