Comparative study between the standard type I and the type A femtosecond laser induced refractive index change in silver containing glasses

International audienceThe femtosecond direct laser writing technique in glasses has been widely used and extensively studied during the last two decades. This technique provides a robust and efficient way to directly inscribe embedded 3D photonic devices in bulk glasses. Following direct laser writing, a local refractive index change (Δn) is induced that is generally classified under three distinguished types (type I, type II & type III). Each type allows for the fabrication of its own variety of 3D photonic components. However, in silver containing glasses, direct laser writing induces the creation of a new type of refractive index change, called type Argentum (type A). It is based on the creation of silver clusters that allow for the creation of optical waveguides. In this paper, we report that both type I and type Argentum modifications could be triggered in silver containing glasses by finely choosing the inscription parameters. A comparative study between both types of single mode waveguides is presented taking into account the morphology, Δn profile and the guided mode profile. Finally, we highlight the originality of type Argentum waveguides paving the way for promising applications not accessible by type I waveguides