Microbolometer Detector Research Articles

Microbolometer in space: IASI and PICASSO-CENA

Microbolometers are infrared detectors of an emerging technology mainly developed in US and few other countries for few years. The main targets of these developments are low performing military and civilian applications like survey cameras. Applications in space are now arising thanks to the design simplification and the associated cost reduction allowed by this new technology. The paper describes two applications in development in SODERN: 1. an infrared camera for the Infrared Atmospheric Sounding Interferometer (IASI): this camera integrated in IASI is used to take pictures of the main instrument field of view and to correlate them with other instrument measurements; 2. an infrared radiometer for PICASSO-CENA based on the same camera design. In both cases, the use of microbolometer detectors leads to very competitive designs in terms of volume, mass, power consumption and cost.

348-GHz endfire slotline antennas on thin dielectric membranes

Tapered slotline endfire antennas, of the broken linearly tapered type, have been fabricated on 1.7- mu m-thin SiO/sub 2/-Si/sub 3/N/sub 4/ ( epsilon /sub r/=4.5) membranes. Antenna patterns in the E-, H-, D-, and D-cross planes have been measured at the design frequency of 348 GHz, with bismuth microbolometer detectors. The antennas have approximately 12-dB directivity, and the -10-dB beam widths are 50 degrees and 56 degrees in the E- and H-planes, respectively. The 348-GHz measurements have been compared with model measurements at 45 GHz, and show good agreement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Twin slot antenna structures integrated with microbolometer detectors for 94‐GHz imaging

AbstractThe twin slot antenna on a dielectric stack should find application in the far‐infrared spectral region. We present measurements at 94 GHz which show that this antenna will be useful as an imaging element.Based on these results, in combination with a new detector element, a two‐dimensional FIR imaging array is proposed.

Millimeter wave twin slot antennas on layered substrates

We have constructed a planar, monolithic twin slot antenna integrated with a bismuth microbolometer detector for operation near 94 GHz. In this paper, we briefly discuss the theory of operation for planar antennas on a dielectric stack. We then cover the fabrication details, including a short discussion of a photoresist bridge technique used to fabricate the microbolometer detectors. Measured receiver gain beam patterns are then compared with theoretical patterns for a number of cases.

Far-infra-red microbolometers made with tellurium and bismuth

The properties of bismuth and tellurium microbolometers are presented. The TE devices are shown to have responsivitics approximately 100 times that of the more conventional Bi microbolometers. The Te device impedance is, however, much larger than Bi microbolometers of comparable size. To our knowledge, the Te device has the highest responsivity yet reported for a microbolometer detector.

Determination of the two-dimensional density distribution in a tokamak plasma using phase-imaging interferometry (invited)

Conventional interferometer systems used on fusion devices are typically limited to approximately ten channels or views, thus precluding the use of tomographic reconstruction techniques. Instead, a priori assumptions have to be made in order to obtain the electron density distribution. To overcome these problems, interferometer systems have been developed at the University of California, Los Angeles (UCLA), which use imaging techniques to provide many channels per probe beam. Using a two-dimensional, 40-channel, imaging far infrared (FIR) interferometer measurements have been made of the density distribution in the minor cross section of the UCLA Microtor tokamak. The heterodyne interferometer consists of two probe beams expanded so as to completely fill orthogonal views of the plasma cross section. These views are then imaged onto two 20-channel, linear microbolometer detector arrays. Using data from this system, the spatial electron density distribution in a tokamak plasma has been recovered for the first time using tomographic reconstruction techniques.

Application of far-infrared, integrated detector arrays to chord-averaged plasma measurements (invited)

The recent development of linear, monolithic microbolometer detector arrays for the far infrared has led to the construction of active imaging diagnostics for tokamak plasmas. Detector arrays have an advantage over discrete detectors in that the cost per detector is significantly reduced since many detectors are fabricated simultaneously. Also, the plasma can be probed with a higher spatial resolution than conventional discrete-beam systems because of the higher channel density. Another advantage is provided by the increased channel number which is important to chord-averaged measurements since it allows an increase in the accuracy of the calculation of Abel inversions of the measured line density profile which are used to reconstruct the actual electron density distribution. The usefulness of this technique has been demonstrated on the UCLA Microtor tokamak (a=11 cm, BT =20 kG, I=70 kA, ne =5×1013 cm−3) in which a 20-channel heterodyned interferometer at wavelengths of 800 and 1000 μm has been used to study the behavior of the plasma profile. Line density profiles during the startup phase of the tokamak discharge have been obtained, as well as sawtooth fluctuation profiles. The imaging technique can also be applied to Faraday rotation measurements of the poloidal magnetic field in the tokamak. A 20-channel polarimeter has been developed that operates simultaneously with the multichannel interferometer.

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.