I. Introduction
Next generation imaging spectrometers for far-infrared astronomy [1]–[4] will benefit from the development of compact on-chip terahertz (THz) filter-banks [5]–[7] with a spectral resolution matched to the typical emission linewidth of extra-galactic sources of [1]. This advancement will allow the construction of true integral field units [8], which are crucial for the tomographic mapping of the early Universe [9]–[11], but are yet nonexistent in the far-infrared regime.