Broadband IR sources are thermal radiators, gas discharge lamps, and infrared LEDs. Infrared lasers serve as monochromatic and coherent sources. Terahertz radiation falls between infrared radiation and microwaves on the electromagnetic spectrum. Terahertz radiation penetrates many materials, such as paper, plastic, and organic tissue, and is therefore suitable for applications in spectroscopy, non-destructive material testing, and safety engineering.
IMPATT diodes are high-power sub-THz radiation sources.
The FIR-/THz lasers are optically pumped lasers used in applications where coherent radiation in the range of 40 μm to 1.22 mm (0.25 –7.5 THz) is required.