Microwave holography - Principle and applications

Holography is a fascinating imaging technique because it aims to produce a three-dimensional image of an object. Its early development was closely linked to the invention of the laser by T. Maiman, a coherent light source, which made it possible to produce the first holographic images based on the principle set out by D. Gabor in 1947. However, this technique remained confined to laboratories until the invention of incoherent white light holography. The subsequent use of digital holography ensured its widespread use, leading to the production of animated holographic images today.

In microwaves, it initially used technologies developed for radar and analog telecommunications, in particular the principle of coherent modulation and demodulation. This enabled the development of three-dimensional microwave imaging, notably that of synthetic aperture radar. This made it possible to detect buried objects and visualize entire cities hidden in the jungle in three dimensions.

The advent of digital technology has further broadened its range of applications. Currently, its applications range from terrestrial and space mapping to brain imaging and holographic antennas and metasurfaces. They are currently used in telecommunications as well as for encrypted data recording. The frequency range covered extends from GHz to THz. All these points are detailed in this article.

A glossary of terms used can be found at the end of the article.