The Terahertz frequency band is largely unexplored both for astronomical and for ground based applications. Over the recent years significant progress has been made in developing coherent detection techniques applicable at these higher frequencies, which enabled the building of array-receivers. When located in a focal plane a telescope such novel systems allow for a manifold increase in performance. However, the development of coherent detector focal plane arrays is still lagging behind. For incoherent bolometric arrays, a novel kinetic inductor detector (KID) has been recently proposed. It makes it possible to multiplex focal plane arrays with many thousands of pixels in very efficient and cost effective way. Backend technologies for both coherent and KID focal plane array will be based on Fourier Transform Spectrometer digital technique, which has demonstrated impressive progress during last few years and ready for large scale arrays. We propose to develop an advanced side band separating mixer technology for focal plane arrays in combination with research directed to increase the operation frequency of superconductor-insulator-superconductor technology by studying new superconducting materials. This research will be combined with development of many kilo pixel KID array. This inter-disciplinary research will enable building large focal plane arrays for use in astronomy and other Terahertz applications.