Cr: LiSrAlF6 optical waveguides defined by ion beam implantation

Planar optical waveguides have been fabricated in the laser material Cr:LiSrAlF₆ using ion implantation. The 2 MeV He⁺ implant forms a low refractive index optical barrier at the end of the ion range, with an index decrease of ∼ 2.5% for a dose of 2 × 10¹⁶ ions/cm² at 77 K. The index at the surface (electronic stopping region) is slightly increased by ∼ 0.15%. Post-implant thermal, and pulsed laser surface annealing have been carried out and compared. It is shown how pulsed laser annealing can remove scattering features from the waveguide surface. Waveguide losses have been measured at 488 and 633 nm by end-fire coupling, and are in the region of a few dB/cm. The waveguide absorption spectrum measured by white light end-coupling has been determined, and suggests that the charge state of the Cr³⁺ remains predominantly unchanged. The study shows that ion implantation is a possible way for making Cr:LiSrAlF₆ waveguide lasers.