Effects of Hydrogen Ion Implantation and Thermal Annealing on Structural and Optical Properties of Single-crystal Sapphire.

ABSTRACTDue to its outstanding thermal and chemical stability, single-crystal sapphire is a crucial material for high-temperature optical sensing applications. The potential for using hydrogen ion implantation to fabricate stable, high temperature optical waveguides in single crystal sapphire is investigated in this work. Hydrogen ions were implanted in c-plane sapphire with energies of 35 keV and 1 MeV and fluences 1016-1017/cm2. Subsequent annealing was carried out in air at temperatures ranging from 500˚C to 1200˚C. Complementary techniques were used to characterize the samples, including ellipsometry and prism coupling to examine optical properties, Rutherford backscattering/ion channeling for crystal defects, and nuclear reaction analysis for hydrogen profiling. Several guiding modes were observed in H-implanted (1 MeV) samples annealed above 800˚C through prism coupling, and a maximum index modification of 3% was observed in the 35 keV samples and 1% in the 1 MeV samples through ellipsometry, with the 1 MeV index variation being confirmed through prism coupling. The possible causes of the index modifications, such as H related defects, as well as implications for tailoring the refractive index of sapphire are discussed.