Liquid identification by Hilbert spectroscopy

Abstract

Fast and reliable identification of liquids is of great importance in, for example, security,biology and the beverage industry. An unambiguous identification of liquids can be madeby electromagnetic measurements of their dielectric functions in the frequencyrange of their main dispersions, but this frequency range, from a few GHz to afew THz, is not covered by any conventional spectroscopy. We have developed aconcept of liquid identification based on our new Hilbert spectroscopy and high-Tc Josephson junctions, which can operate at the intermediate range from microwaves to THzfrequencies. A demonstration setup has been developed consisting of a polychromaticradiation source and a compact Hilbert spectrometer integrated in a Stirling cryocooler.Reflection polychromatic spectra of various bottled liquids have been measured at thespectral range of 15–300 GHz with total scanning time down to 0.2 s and identification ofliquids has been demonstrated.