Fig. 1. Principles of evanescent wave. (a) Normal fiber; (b) tapered fiber

Fig. 2. Experimental setup for ethanol solution detection with chalcogenide tapered fiber

Fig. 3. Infrared transmission spectrum of Ge15Sb20Se65 glass (thickness is 2 mm)

Fig. 4. Loss of Ge15Sb20Se65 bare glass fiber with a core diameter of 500 μm (The inset is an image of the cross-section of the fiber)

Fig. 5. Surface images of Ge15Sb20Se65 tapered fiber-III. (a) Tapered transition; (b) taper waist

Fig. 6. IR spectra of bare fiber and tapered fibers for measuring ethanol solution with different volume fractions. (a) Untapered fiber; (b) tapered fiber I; (c) tapered fiber II; (d) tapered fiber III

Fig. 7. Relationship between absorbance and different volume fractions of ethanol solution at 9.53 μm with bare fiber and tapered fibers. (a) Untapered fiber; (b) tapered fiber I; (c) tapered fiber II; (d) tapered fiber III

Fig. 8. Relationship between absorbance and low volume fraction of ethanol solution at 9.53 μm with tapered fiber III

Fig. 9. Simulation of relationship between light intensity of optical receiving end and different volume fraction of ethanol solution with the bare fiber and taper fibers