submillimeterradiation

Submillimetre radiation, or submillimetre radiation, refers to electromagnetic radiation with wavelengths roughly between 0.1 and 1 millimetre, corresponding to frequencies about 0.3 to 3 terahertz. This band lies between the far-infrared and microwave parts of the spectrum and is important for thermal emission from cold dust as well as rotational transitions of many light molecules.

Generation and detection in this band rely on a mix of techniques. In the laboratory, submillimetre radiation is produced by frequency multipliers, solid-state oscillators, quantum cascade lasers, or systems that mix signals to lower frequencies. Detection uses bolometers and superconducting sensors such as transition-edge sensors (TES) and kinetic inductance detectors (KIDs), as well as heterodyne receivers that employ superconducting-insulator-superconducting (SIS) or hot-electron bolometer (HEB) mixers to achieve high spectral resolution.

Atmospheric transmission is a key consideration because Earth’s atmosphere strongly absorbs submillimetre waves, especially at lower altitudes. Observations are therefore conducted from high-altitude sites, airborne platforms, balloon missions, or space. Major facilities include ground-based observatories such as ALMA (Atacama Large Millimeter/submillimeter Array) and other telescopes operating in the submillimetre window, along with space missions carrying submillimetre instruments.

Applications and significance: Submillimetre radiation is central to astronomy and cosmology because it reveals cold interstellar dust, star-forming regions, and molecular gas through emission lines such as rotational transitions of CO and other molecules. It is also used in laboratory spectroscopy and imaging, with applications in materials science and chemical sensing.