Effect of uniform helium doping on the optical properties and laser damage performance of sapphire

Sapphire samples have been implanted successively by helium ions with a series of energies to obtain a uniform layer of impurities in the range of 80-200 nm beneath the surface at room temperature. After helium ion implantation, the surface morphology has been greatly changed. In addition, two broad absorption bands at 360 nm and 780 nm are observed and their intensities significantly increase. An infrared band shifts from 782 cm^-1 to 760 cm^-1 and the band obviously broadens. Moreover, a luminescence band at 330 nm (3.8 eV) is associated with the 2P→1S* transition of the F⁺ centers. After laser irradiation, the laser damage morphologies of samples before and after ion implantation are presented. An obvious degradation of laser induced damage threshold (LIDT) is observed and the mechanism for the degradation of LIDT is discussed. (author)