High-temperature recrystallization effects in swift heavy ion irradiated KY(WO4)2

Abstract

KY(WO 4 ) 2 crystal has a lot of potential as an on-chip waveguide material for lanthanide ion-doped, Raman active lasers and on-chip amplifiers. One method of fabricating these waveguides is by using swift carbon ion irradiation, which produces a step-like, damageinduced refractive index contrast of up to Δn % 0.2. The irradiation is followed by an annealing step to reduce color centers that cause high optical absorption, leading to an optical slab waveguide with optical transmission losses as low as 1.5 dB/cm at 1550 nm. In this article, we report an upper limit of 450 C to the annealing temperature, above which stresses and recrystallization induce additional scattering detrimental to waveguide performance. The effects are characterized using transmission electron microscopy and Raman microscopy.