Air-bridge microbolometer for far-infrared detection

A new microbolometer for far-infrared detection has been fabricated that allows an increase in sensitivity of a factor of 4 over the best previously reported bolometer. By suspending the detector in the air above its substrate a reduction in the thermal conductance out of the device by a factor of 5 has been achieved. At a modulation frequency of 100 kHz this microbolometer has an electrical noise equivalent power of 2.8×10^−11 W(Hz)^−1/2. A thermal model is also presented that accurately fits the response of the detector

Self-heated thermocouples for far-infrared detection

A novel self-heated Bi-Sb thermocouple for far-infrared detection has been developed. The detector is suitable for integration with monolithic antennas and imaging arrays. The device is fabricated in a single photolithography masking step using a photoresist-bridge technique. This bridge technique has also been used to make microbolometers with lower 1/f noise than those made by two conventional masking steps. The thermocouples have a noise equivalent power (NEP) of 7×10^−10 W/(√Hz) and a 3-dB frequency response of 150 kHz

Semiconductor device apparatus having multiple current-voltage curves and zero-bias memory

Heterostructure barrier quantum well device with a super-lattice structure of alternating lightly doped and heavily doped spacer layers having multiple, stable current-voltage curves extending continuously through zero bias at ambient temperature. The device can be repetitively switched between the multiple current-voltage curves. Once placed on a particular curve, the device retains memory of the curve it has been set on, even if held at zero bias for extended periods of time. The device can be switched between current-voltage curve settings at higher positive or negative voltages and can be read at lower voltages. Switching between current-voltage curve settings can also be effected by additional terminal connection(s) to the spacer layer(s).Board of Regents, University of Texas Syste

Sublimating and cracking apparatus

A furnace having a sublimating section, a cracking section oriented off axis to the sublimating section, and a valve for controlling flux between the sections. The valve includes an annular plug having at least one longitudinal slot. The plug is retractable from a fully closed position where the slot is completely covered, to a fully open position where the slot is completely exposed. The slot becomes increasingly exposed as the plug is moved from the fully closed position to the fully opened position, thereby increasing flux from the sublimating section to the cracking section.Board of Regents, University of Texas Syste

Corrosion detection sensor embedded within a concrete structure with a diffusion layer placed over the sacrificial transducer

A corrosion detection sensor embedded within a concrete structure. The sensor includes a hermetically sealed resonant circuit that is a resistor-inductor-capacitor (RLC) circuit. The sensor further includes a sacrificial transducer that is inductively or capacitively coupled to the resonant circuit, where the sacrificial transducer is exposed to an environment outside the sensor to monitor corrosion of steel reinforcement in the concrete structure. Additionally, the sensor includes a protective cementitious housing surrounding the resonant circuit and the sacrificial transducer. The sensor further includes a diffusion layer placed over the sacrificial transducer, where the diffusion layer enables a dispersion of a chemical species over the sacrificial transducer. In this manner, a more uniform distribution of the chemical species over the surface of the sacrificial transducer mitigating the localized corrosion is ensured. Furthermore, such a design is less susceptible to false positives.Board of Regents, University of Texas Syste

Imaging Polarimeter Arrays for Near-Millimeter Waves

An integrated-circuit antenna array has been developed that images both polarization and intensity. The array consists of a row of antennas that lean alternately left and right, creating two interlaced sub-arrays that respond to different polarizations. The arrays and the bismuth bolometer detectors are made by a photoresist shadowing technique that requires only one photolithographic mask. The array has measured polarization at a wavelength of 800 µm with an absolute accuracy of 0.8° and a relative precision of 7 arc min. and has demonstrated nearly diffraction-Iimited resolutiort of a 20° step in polarization

Tracking antenna arrays for near-millimeter waves

A two-dimensional monolithic array has been developed that gives the elevation and azimuth of point source targets. The array is an arrangement of rows and columns of antennas and bismuth bolometer detectors on a fused quartz substrate. Energy is focused onto the array through a lens placed on the back side of the substrate. At 1.38 mm with a 50 mm diameter objective lens, the array has demonstrated a positioning accuracy of 26 arcmin. In a differential mode this precision improves to 9 arcsec, limited by the mechanics of the rotating stage. This tracking could be automated to a fast two-step procedure where a source is first located to the nearest row and column, and then precisely located by scanning. With signal processing the array should be able to track multiple sources

Imaging antenna array at 119 µm

A focal-plane imaging antenna array has been demonstrated at 119 µm. The array is a line of evaporated silver bow-tie antennas with bismuth microbolometer detectors on a silicon substrate. Radiation is coupled into the array by a lens placed on the back of the substrate. The bolometers are thermally isolated from the silicon substrate with a half-micron layer of polyimide. The array performance is demonstrated by coherent imaging of a series of holes at half the diffraction-limited cut-off frequency

Far-infrared imaging antenna arrays

A far-infrared imaging antenna array has been demonstrated for the first time. The array is a line of evaporated silver bow-tie antennas on a fused-quartz substrate with bismuth-microbolometer detectors. The measured optical transfer function shows that the system is diffraction limited. This imaging array should find direct application in fusion plasma diagnostics. If the microbolometers can be replaced by more sensitive diode detectors, the array should also find application in radiometry and radar