An uncooled microbolometer focal plane array (FPA) has been developed and used for imaging of objects illuminated by monochromatic coherent radiation of a free electron laser tunable in the range of 1.25–2.5THz. A sensitivity threshold of 1.3×10−3W∕cm2 was obtained for the FPA with a homemade absolute interferometric power meter. Videos up to 90frames∕s were recorded in both transmission and reflection/scattering modes. When objects were illuminated by laser radiation scattered by a rough metal surface, speckled images were observed. Good quality terahertz images were achieved through the fast rotation of the scatterer.
Gradually appearing high-power terahertz sources require the development of adequate imaging techniques. This paper describes four imaging techniques (with a thermal recorder, temperature-sensitive phosphor plates, a visible-light thermal sensitive Fizeau interferometer, and an uncooled microbolometer array) applied with the Novosibirsk terahertz free electron laser as a radiation source. The space and time resolutions of the devices were examined thoroughly. Examples of the application of these techniques, including in-line holography and real-time moving-objects detection, are given.
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