Sensitivity of Reflecting Terahertz Sensors of Aqueous Solutions

Sensitivity of sensors of aqueous solutions in which a terahertz signal is reflected from a structure consisting of a dielectric film and solution is studied. The maximum sensitivity is reached at angles of incidence and radiation frequencies that provide zero reflection of monochromatic radiation from the specified structure. Conditions for such reflection are determined for the s- and p-polarized radiation. The calculated results are proven by experimental data for a sensor of glucose in water in which a thin silicon film separates the solution from air. For the time-domain terahertz spectroscopy, the proposed sensor structure allows reliable detection and identification of glucose at concentrations of 10 and 30 g/L.