Ultrafast-laser-inscribed multiscan type-I mid-infrared waveguides and beamsplitters in IG2.

This study reports the fabrication and characterization of various configurations of mid-infrared waveguides and beamsplitters within the chalcogenide glass IG2 using ultrafast laser inscription (ULI). Our investigation reveals two distinct regimes of ULI modification: weak and strong. The strong regime, marked by higher pulse energies, presents darker and prominent waveguide morphology, enabling efficient light guiding at 4.55 µm, but with higher scattering losses at shorter wavelengths. In the weak regime, we observed a significant enhancement in the mode confinement and a reduction in the propagation loss within the multilayer structures. We have investigated key geometric and inscription parameters such as inscription pulse energy and number of layers, as well as arm separation and splitting angles for beamsplitters. We have successfully fabricated beamsplitters with configurations ranging from 1 × 2 to 1 × 8, achieving a uniform splitting ratio over 96% and a splitting loss as low as 0.4 dB at 4.55 µm. These findings highlight the significant potential of ULI-based IG2 waveguides and beamsplitters for mid-infrared photonics.