Figure 3
The waveguide mode images were captured from λ = 2.5 µm to 3.2 µm with or without chemicals covering the waveguide. Fundamental modes were clearly observed over a broad spectral range. When heptane was presented, the mode disappeared at λ = 3.0 µm–3.2 µm corresponding to -CH absorption. For methanol, the mode vanished at λ = 2.8 µm–2.9 µm associating with -OH absorption. The mode intensities recovered when the analytes evaporated from the waveguide surface.
