Fig. 1. (a) Setup used for the sensing experiments. The top spirals are exposed to the liquid (sensing arm), while the bottom ones are cladded and act as a reference. PIC, photonic integrated circuit; PM, phase modulator; PD, photodetector; PC, personal computer. (b) SEM micrograph of the spirals area.

Fig. 2. Real-time refractive index sensing for IPA-in-water solutions. Phase shift versus time is reported for different IPA-in-water concentrations.

Fig. 3. Phase shift versus time for different glycerol concentrations in water.

Fig. 4. Measured response for different concentrations of glycerol (circles) and IPA (triangles). Linear fits of the response versus concentration for each case are also shown.

Table 1. Refractive Index Values (at 1.55 μm) of IPA and Glycerol Aqueous Solutions at Low Concentrations, Together with Effective Index Variation Calculations and Expected Phase Response Extracted from Eq. (1)