Sensitivity of reflecting terahertz sensors of aqueous solutions

Sensitivity of sensors of the composition of aqueous solutions in which it is detected the terahertz pulse reflected from the dielectric film – solution structure is investigated. It is shown that the maximum of the sensitivity is achieved by choosing the angles of incidence and radiation frequencies, providing zero reflection of monochromatic radiation from the named dissipative structure. Conditions for the realization of such reflection for waves of $s$- and $p$-polarization are established. Calculations are confirmed experimentally for the sensor of glucose concentration in water, which uses a thin silicon wafer, separating solution from air. It is shown that with the use of the terahertz time-domain spectroscopy method the sensor of the proposed structure allows reliable to detect and distinguich glucose impurities of concentration 10 and 30 g/l.