Bolometri

Bolometri, or bolometers in English, are detectors that measure electromagnetic radiation by converting absorbed power into heat. An absorber captures incident photons, causing a rise in temperature that is sensed by a temperature-sensitive element. The signal is proportional to the incoming power integrated over the detector's spectral band.

A bolometer is typically thermally isolated from its surroundings, connected to a heat sink by a weak thermal link. The temperature change delta T is given by delta T = P_in / G, where P_in is absorbed power and G is the thermal conductance. The readout often uses a resistive thermometer, such as a semiconductor thermistor or a superconducting device, whose resistance changes with temperature. The device's sensitivity is quantified by the noise equivalent power (NEP).

Bolometers come in several families. Thermal, or resistive bolometers, use a thin absorber on a membrane. Microbolometers are compact infrared cameras. Superconducting bolometers, including transition-edge sensors (TES) and kinetic inductance detectors (KID), operate at cryogenic temperatures and offer high sensitivity for astronomy in the far-infrared to millimeter range.

Applications include astronomical observations of dust and cosmic background radiation, infrared imaging for surveillance and industrial inspection, spectroscopy in the terahertz domain, and other scientifically sensitive measurements.

Performance factors include absorptivity, heat capacity, thermal conductance, NEP, and response time. Materials range from doped silicon and vanadium oxide to superconducting films; many systems require cooling to tens of kelvin or below.