Transition Edge Thermometer Research Articles

Fabrication and measurement of high T/sub c/ superconducting microbolometers

The authors fabricated and measured the performance of antenna-coupled microbolometers based on the resistive transition of a high-T/sub c/ superconducting film for use as detectors of far-infrared and millimeter waves. A planar lithographed antenna (log-periodic or log-spiral) is used to couple the radiation to a thin YBCO film with dimensions ( approximately=6*13 mu m/sup 2/) which are smaller than the wavelength to be measured. This film acts both as the resistor to thermalize the RF currents and as a transition edge thermometer to measure the resulting temperature rise. Because of its small size, both the thermal conductance from the film into the bulk of the substrate and the heat capacity of the thermally active region are small. Consequently, the microbolometer has low noise, fast response, and a high voltage responsivity. A phonon-limited electrical NEP of 4.5*10/sup -12/ WHz/sup -1/2/ at a 10-kHz modulation frequency and a responsivity of 478 V/W at a bias of 550 mu A were measured. Measurements of the optical efficiency are discussed.

Fabrication of an infrared bolometer with a high T/sub c/ superconducting thermometer

A sensitive high-T/sub c/ superconducting bolometer has been fabricated on a 20- mu m-thick sapphire substrate with a YBCO thin-film transition edge thermometer. Optical measurements with a He-Ne laser gave a noise equivalent power of 2.4*10/sup -11/ W/Hz/sup 1/2/ at 10 Hz, and a responsivity of 17 V/W in good agreement with electrical bolometer measurements. Gold black smoke was then deposited on the backside of the assembled bolometer as an absorber. Spectral measurements on a Fourier transform spectrometer show that the bolometer has useful sensitivity from visible wavelengths to beyond approximately 100 mu m. This performance is superior to that of a commercial room-temperature pyroelectric detector. Some improvement appears possible.