Fig. 1. Schematic illustration of the layer structure of samples used in this work and an illustration of the transverse profile of photo-induced refractive index changes in the core As2S3 glass layer.

Fig. 2. Schematic illustration of the setup used in measurements of the photo-induced refractive index change in As2S3 films.

Fig. 3. Top: OVA measurements of the transmission of light through the layers of a silica-on-silicon sample coated with an As2S3 film (see Fig. 2). The red (blue) curve corresponds to a region outside (within) a photo-darkened area. Bottom: spectral offset in nanometers between peaks of maximum transmission outside and within the photo-darkened area. The linearly increasing offset corresponds to an increase in the refractive index within the photo-darkened region by 0.4 RIU.

Fig. 4. Calculated effective indices (red) and group indices (blue) of the fundamental modes of directly written waveguides in As2S3 thin films, as a function of the photo-induced refractive index change in the core region . Solid (dashed) lines correspond to the TM (TE) mode.

Fig. 5. Top-view microscope image of parts of bus and ring waveguides, directly written in a thin layer of As2S3.

Fig. 6. Top view of a ring resonator waveguide, directly written in an As2S3 thin film. Red light is coupled from a tapered fiber for illustration purposes only.

Fig. 7. OVA measurement of the temporal impulse response of a ring resonator of 1.888 mm radius, directly written in a thin film of As2S3.

Fig. 8. Top: OVA measurement of the spectral power transfer function of a ring resonator of 1.888 mm radius, directly written in a thin film of As2S3. Bottom: magnified view of a single transmission notch, with a FWHM of 0.014 nm.

Fig. 9. OVA measurements of the spectral power transfer function of a ring resonator of 1.888 mm radius, at several temperatures (in °C, see legend). The resonance wavelengths are offset by 0.022 nm/°C.