Fig. 1: Preparation and characterization of optical waveguides (OWGs) in glass.

a Schematic of femtosecond laser direct writing of OWGs in glass. b Top and (c) side view of OWGs. d The mode field images of OWGs in the range from visible to near-infrared range. Scale bar: 10 μm. The color bar represents the normalized intensity of light passing through the OWGs.