High performing designer glass platform to host versatile photonic devices

The aluminum to alkaline earth ratio (Al:[AE]) in borosilicate glass is introduced as a novel compositional parameter to produce high index waveguides through femtosecond laser inscription. Alkaline earths are considered to be major refractive index providers for laser written optical waveguides due to their collective migration toward the guiding region. Contrary to the existing belief that increasing the concentration of such index providers within a glass composition will help to produce high index change waveguides, we demonstrate that high index waveguides can be fabricated by tuning the Al:[AE] ratio while keeping the absolute concentration of the index provider to a minimum.