THz Detection Techniques Overview

In re­cent years, the THz part of the elec­tro­mag­netic spec­trum has at­tracted spe­cial at­ten­tion due to the broad range of pos­si­ble ap­pli­ca­tions de­riv­ing from it and its pres­ence in mul­ti­ple nat­ural phe­nom­ena. T-rays are able to pass al­most un­ob­structed through a wide range of non-po­lar ma­te­ri­als such as fab­rics, paper, wood, ce­ram­ics, plas­tics and plasma. Ra­dioas­tron­omy, spec­troscopy, mol­e­c­u­lar sens­ing, plasma di­ag­nos­tics, se­cu­rity and bio­med­ical imag­ing are only a few pos­si­ble uses of the THz spec­trum. Such wide range of pos­si­ble ap­pli­ca­tions de­mands a sim­i­larly wide range of de­tec­tion tech­niques and de­vices. The meth­ods pre­sented in this overview have been or­ga­nized in four groups, based on the phys­i­cal prin­cipia they rely on: ther­mal, di­rect de­tec­tion, su­per­het and sam­pling de­tec­tion. For each of the tech­niques, the op­er­a­tional lim­its and the most fre­quent ap­pli­ca­tions are also pre­sented.