bolometrische

Bolometrische refers to bolometry, the measurement of radiant energy by absorption and the resulting heating of a material. A bolometer detects electromagnetic radiation across a broad range, from infrared to millimeter and submillimeter wavelengths, by converting the absorbed energy into an electrical signal.

Operating principle: An absorber with heat capacity C captures incident power P_in, causing a temperature rise ΔT. The relation ΔT ≈ E_abs / C governs, where E_abs is the absorbed energy. A sensitive thermometer or transducer—often a thermistor, a superconducting transition-edge sensor (TES), or a kinetic inductance detector (KID)—measures the temperature change, producing an electrical output proportional to the incident power. The detector’s time constant is τ = C / G, with G the thermal conductance to a heat sink. Sensitivity is characterized by the noise-equivalent power (NEP), which depends on temperature, material properties, and readout noise.

Detector types: Bolometers include resistive devices using materials such as vanadium oxide (VOx) or amorphous carbon, and cryogenic superconducting devices like TES and KID arrays. Cryogenic operation, often at tens of millikelvin, greatly enhances sensitivity and lowers NEP, enabling detection of extremely faint signals. Bolometric detectors are frequently deployed in large arrays for imaging.

Applications: Bolometrische detectors are central in astronomy and cosmology, notably in infrared, submillimeter, and microwave observations, including cosmic microwave background experiments and submillimeter surveys. They also find use in security imaging and industrial spectroscopy. Advantages include broad spectral response and high sensitivity; challenges include the need for cryogenic cooling, calibration complexity, and relatively slow response times compared with some alternative detectors.

See also: bolometer, bolometry, infrared astronomy, cosmic microwave background experiments.