Weak Value Amplified Precision Terahertz Spectroscopic Detection of Solid and Liquid Glucose Samples

A novel combination of terahertz time-domain spectroscopy(THz-TDS)and weak value amplification (WVA) is employed to quantify the glucosecontent of various forms, such as glucose thin films with concentrationsfrom 0.01 to 0.10 mg/mL, glucose solutions with concentrations from0.01 to 0.10 mg/mL, and glucose tablets with mass fraction varyingfrom 5.0 to 10.0%, which drastically outperforms the classical THz-TDSdetection technique. The small concentration and mass fraction changesof glucose samples in various forms that are beyond the traditionalTHz-TDS detection limit can be detected by the introduction of WVA.For glucose thin films and solutions, the minimum detectable concentrationdifference is 1-2 orders of magnitude lower and 1-4orders of magnitude lower, respectively, than the previously accessibleTHz limits. The detectable mass fraction gradient of glucose tabletsis comparable to that of previous studies, but the minimum detectablemass fraction in this work is lower. A general theoretical model todescribe the preselected and postselected THz sensing system is established,and the polarization-dependent amplitude and phase evolution inducedby changes in sample concentration or mass fraction are shown to correlatewith the weak interaction between the THz photon and the target moleculesin the WVA formalism. It is shown that WVA significantly suppressesthe technical noise with respect to the intensity difference signalinduced by the changes in sample concentration or mass fraction whenthe preselection and postselection procedures come into play. Thesefindings may be favorable for highly sensitive THz detection, includingminor changes in the parameters of the test object and interactionsbetween biomolecules.