Recent work published in AIP Advanced journal by Agnieszka Siemion et. al reports on advances in Terahertz digital holography implementing two- and four-step phase shifting technique. Proposed holographic technique shows many advantages in THz imaging such as better contrast, reconstruction of 3D image and etc.
The article is open access and can be reached through this link: https://aip.scitation.org/doi/10.1063/5.0062330