Dielectric Bolometer: A New Type of Thermal Radiation Detector*

Abstract

Thermal detectors for the infrared, such as thermocouples and bolometers, are limited in their ultimate sensitivity predominantly by Johnson noise rather than by temperature noise. Low noise figures are hard to achieve, since the Johnson noise dominates temperature noise, which is the only essential noise for thermal detectors. Some materials show a temperature dependence of their dielectric constant sufficiently high to make a new type of bolometer feasible. The basic theory of a dielectric bolometer, as shown here, promises noise figures below 3 db even at chopper frequencies well above the 1/τ value of the detector. Ferroelectrics such as barium-strontium titanate and others seems to be well suited for radiation-cooled dielectric bolometers.