Indium Antimonide Detector Research Articles

The Moon as a light source for FTIR measurements of stratospheric trace gases during the polar night: Application for HNO3 in the Arctic

A Fourier Transform Infrared (FTIR) spectrometer has been used with the Moon as an IR light source to derive column densities of stratospheric trace gases. The measurements were performed during the polar night in the Arctic winter 1992/1993 at the Network for Detection of Stratospheric Change (NDSC) station in Ny‐Ålesund (79°N, 12°E) located at Spitsbergen. Because of the emission of the Moon itself it was possible to use not only the Indium Antimonide (InSb) detector for the wavenumber region 2600–4000 cm−1 but also the less sensitive Mercury Cadmium Telluride (MCT) detector covering the interval 600–1000 cm−1. Solar OH lines, missing in the lunar spectra, demonstrate the contribution of the Moon's emission effect to the overall infrared intensity. The measurements could be performed for about a week around the full Moon. Spectra were recorded at 0.01 cm−1 or 0.02 cm−1 resolution. It was possible to derive zenith column densities of N2O, CH4, C2H6, HF, HCl, O3, NO2, HNO3, and ClONO2. They were retrieved using a version of the FASCOD2 program for personal computers or the retrieval of atmospheric trace gas profiles (RAT) program. Spectral data were taken from the HITRAN92 database. Lunar observations for HNO3, performed in December 1992 and February 1993, are compared with solar observations from March 1992 and March–July 1993 performed at the same location. Our measurements at 79°N agree with literature results for this trace gas. Owing to the occurrence of the polar night and polar summer, the seasonal cycle in the column densities of HNO3 is found to be more pro‐nounced in the Arctic than at midlatitudes. Although polar stratospheric clouds (PSCs) were frequently observed throughout the winter, the data do not indicate a significant removal of HNO3 from the atmosphere by sedimentation via PSCs. A denitrification, the irreversible removal of NOx, as observed during the winter in Antarctica, did not occur.

Noninvasive Glucose Monitoring in Diabetic Patients: A Preliminary Evaluation

Noninvasive monitoring of blood/tissue glucose concentrations has been successfully accomplished in individual diabetic subjects by using near-infrared (NIR) spectroscopy coupled with chemometric methods. Three different spectrometer configurations were tested: a) a Fourier-transform infrared spectrometer with an indium antimonide detector; b) a grating monochromator equipped with a silicon (Si) array detector, without fiber optics; and c) a grating monochromator equipped with an Si detector, with fiber-optic sampling. NIR spectra were obtained from diabetic subjects by transmission through the finger during a meal-tolerance test. The maximum range of observed plasma glucose concentrations obtained from the blood samples was 2.5-27 mmol/L. The NIR spectra were processed by using the chemometric multivariate calibration methods of partial least squares and principal component regression. The best calibration yielded a cross-validated average absolute error in glucose concentration of 1.1 mmol/L. This predictive ability suggests that noninvasive glucose determinations by NIR/chemometrics is a viable analytical method.

Evaluation Of An Indium Antimonide Hybrid Focal Plane Array For Ground-Based Infrared Astronomy

A new hybrid infrared array sensitive in the 1 to 5µm spectral region has recently become generally available to the astronomy community. It is a composite (hybrid) array using photovoltaic indium antimonide detector material bump-bonded to a silicon substrate that contains the MOS direct readout multiplexer. This paper describes the array, its operation, and preliminary results on quantum efficiency, dark cur-rent, noise, linearity, cosmic ray response, and imaging characteristics as they apply to ground-based astronomy. The tests were performed on an engineering device since scientific devices are not yet available. Based on our results, we believe that this array and others like it will affect infrared astronomy to an even greater extent than CCDs affected optical astronomy in the mid-1970s.

Measurement of the temperature profile during shear band formation in steels deforming at high strain rates

A torsional Kolsky bar (split-Hopkinson bar) was used to deform tubular specimens of AISI 1018 cold rolled steel and AISI 1020 hot rolled steel at a nominal strain rate of 10 3s −1. Shear bands were observed to form in both steels, and the temperature of the material in the bands was measured by determining the infrared radiation emitted at the metal surface. For this purpose, a linear array of ten indium-antimonide detectors was used to determine temperature history at ten neighboring points lying across the projected path of the shear band. Results showed that shear bands in these steels are relatively wide, that the maximum temperature rise in the band is about 450°C and that the temperature distribution across the band is consistent with results of stability analyses. The two steels have very different work hardening rates and the strain at which localization is first observed is very different for the two steels : in the cold-rolled steel it occurs at about 15% strain, while in the hot-rolled the strain is near 100%. This result also is consistent with predictions of the analyses.

Grating spectrometer installation for electron cyclotron emission measurements on the DIII-D tokamak using circular waveguide and synchronous detection

The grating spectrometer installation on the DIII-D tokamak uses fundamental circular waveguide propagating the TE11 lowest-order mode followed by oversized circular guide carrying the low-loss TE01 mode. The short section of fundamental guide permits use of an electronic chopper operating at 100 kHz for both calibration and plasma operation. By using ac-coupled amplifiers tuned to the chopping frequency, the background signal generated in the indium antimonide detectors by neutrons and x rays is automatically subtracted and the system noise bandwidth is reduced. Compared with a quasi-optical system, the much smaller fundamental horn and front-end waveguide allow the waveguide system to be located outside a gate valve. With this configuration the entire waveguide run, including the actual horn and vacuum window used during plasma operations, can be included in the calibration setup.

New infrared detectors

Scientists at General Electric's Research and Development Center in Schenectady, N.Y., have developed a new process for manufacturing indium antimonide detectors that will allow them to be used in infrared space satellites for the first time. The process reduces impurities in the detectors and so decreases their “noise” level.In order to make sensitive infrared observations, detectors using conventional indium antimonide must be operated at temperatures below −184°C, which require liquid nitrogen or liquid helium for cooling. The new detectors will operate effectively at temperatures as high as −151°C, however, and can be maintained indefinitely by satellite refrigeration systems powered by onboard solar cells.

Low-noise In-Sb photodetector preamp for the infrared

A low-noise, cryogenically cooled preamplifier has been designed and built for indium antimonide detectors used in IR astronomy. General noise and frequency response equations for the transimpedance amplifier are derived. The effects of finite open-loop gain and bandwidth and of photodetector parameters on circuit performance are shown. A current-injecting background cancellation scheme based on optical feedback and synchronous filtering is described. Total electrical NEP figures as low as 10/SUP -16/ W (at 5 /spl mu/m) and background rejection ratios higher than 3000:1 have been measured using a 0.5 mm diameter detector.

Impact of Surface Treatment on the Performance of Cooled Photoconductive Indium Antimonide Detectors

The performance of cooled photoconductive detectors made from high resistivity indium antimonide depends strongly on the state of the semiconductor surface. After seal-off some of the detectors show a degradation in performance due to the bake-out at 110°C in darkness during evacuation of the detector dewar. Irradiating these detectors with high-energy photons improves their performance, while subsequent heating in darkness leads to a new degradation.A number of such detectors have been investigated leading to a theory for this radiation-dependent behaviour. Some field-effect measurements are performed to confirm the theory. The investigations on the low performance detectors also result in procedures for surface treatments giving a better yield of high performance detectors.

Fast current amplifier for background-limited operation of photovoltaic InSb detectors

A fast current amplifier for use with photovoltaic indium antimonide detectors is described which was designed for detection of lidar return signals. Near background-limited operation was possible for bandwidths up to 0.8 MHz.

An Attempt to Observe Zodiacal Light at 5μ with a Balloon Experiment

Observations of the infrared emission of the interplanetary dust enable a more direct analysis to be made of interplanetary dust material than is possible from observations of the scattered sunlight. A liquid nitrogen cooled photometer with Indium Antimonide detectors is described which has been developed for balloon-borne observations of the zodiacal light. The provision of both difference and absolute flux measurement modes will allow the observation of the zodiacal light, and the presumably much more intense emission of the high atmosphere, respectively.

Johnson Noise Limited Operation of Photovoltaic InSb Detectors

Photovoltaic indium antimonide detectors have been operated at temperatures </=77 K with sufficiently low background radiation levels that Johnson noise limited performance is realized. Under such conditions the noise equivalent power (NEP) is completely determined by the detector operating temperature, resistance, and quantum efficiency. Optimization of these parameters in the manufacture of commercially available detectors has led to 5-mum NEP's as low as 10(-15) W. The particular preamplifier is critical to the achievement of Johnson noise limited operation and is described in detail.

Fast infra-red detectors for use in pulse radiolysis

This paper summarizes the characteristics of a number of fast response (<1 μs), solid state infra-red detectors now being used for pulse radiolysis studies. Two in particular have proved very satisfactory. These are a silicon photodiode SGD-100A, Edgerton, Germeshausen & Grier Inc., covering the wavelength region 350–1100 nm, and a liquid nitrogen cooled indium antimonide detector, SD-8721-2, Spectronics, Inc., which has a nominal range of 1000–5500 nm. The former has a response time (0–98 per cent) ⩽25ns and the latter (0–100 per cent) ⩽200ns.

5-µm Infrared Emission from Algol

DURING September 1972, we made a number of 5-µm observations of the eclipsing binary β Per (Algol) using the 60-inch infrared flux collector at Izana, Tenerife. Our photometer was of conventional design, having a nodding mirror to give sky background cancellation and using an indium antimonide detector cooled to 77 K. α Per was used as a comparison source and this in turn was calibrated against better known infrared standards such as α Lyr. Poor weather conditions did not allow us to make as many observations as we would have liked, but sufficient to define the principal light curve.

Sewing Needle Temperature

A study has been made of the effect of various needle characteristics on the needle temperature during high-speed sewing without thread. The needle temperatures were determined by means of infrared flux measurements. A very fast indium antimonide detector coupled with a closed-circuit television recording system and the individual determination of needle emissivities overcame almost all the dit1iculties previously associated with this methcxl. Despite the accuracy of the measuring system, there was a fair amount of variation among the needles of a particular group. An average tem perature difference hetween groups of less than 30°F is probably not significant. Xeedle surface finish was found to be the most significant needle variable. Kooltorr R or dark matte surface finishes ran at much lower temperatures than any other finishes, while sewing heavy cotton-duck fabric at 4200 stitches per minute. Nickel, plain steel, and chrome gave increas ing temperatures in that order. There is a moderate, but not completely consistent, effect of higher needle temperatures with increasing diameter. Point type and most other physical variations had very little effect. The range of maximum temperatures for standard 88X 1 size 16 needles was from 640°F for the Kooltorr® to over 800°F for the chrome and nickel finishes.

Continuous Spectrum of Taurus A at 1.2 mm Wavelength

WE have measured the radiation from the region of the Crab nebula (Taurus A) in a waveband centred at 1.2 mm (250 GHz) in the far infrared. Our equipment was an indium antimonide detector of the Rollin1 type cooled by liquid helium at the cassegrain focus of the 98 inch Isaac Newton telescope of the Royal Greenwich Observatory. The observations were made with the aid of a rapid-scan unit, comprising an oscillating mirror which scanned in declination 13.7′ of arc on the sky either side of its axial point with a period of 1.2 s. The effect of the rapid scanning is to increase the discrimination of the system against v−1 components in both sky background and detector electronic noise2. The scans were synchronized, stored digitally and averaged by means of an “enhancetron” digital analyser, which provided a visual display and chart recorder readout.

Emissivity of human skin in the waveband between 2micra and 6micra.

THE emissivity of human skin e(λ) in the range 2µ to 6µ has recently assumed considerable importance because of the increasing medical use of infrared scanners to measure skin temperature (t). Several commercially available scanners utilize indium antimonide detectors which are sensitive in the range 2µ to 5.4µ. Such machines measure the energy (Q) radiated by the skin and, being calibrated against a standard black body, changes in Q are represented as variations in skin temperature. Dreyfus1 has shown that Q is related to t by an equation of the form, where k is a constant, and where the index n depends on λ as λmax being the wavelength corresponding to the maximum in the emission curve. The importance of variations in emissivity can be seen by differentiating equation (1) for constant Q. We obtain which simplifies to give for Δt For a skin temperature of 27° C (t=300° K), n is about 12.5. It follows from equation (2) that if e(λ) were to vary by as much as 5 per cent over the skin surface, this would be interpreted by the scanner as a temperature variation of about 1° C. A fairly accurate knowledge of e(λ) is thus necessary, for hot spots with temperature elevations of only 2° C are considered to be of clinical significance.

A prism line-scanner for high-speed thermography.

Thermographic instruments using single-element line scanning usually have very low line frequencies in comparison with television. To meet the requirements for higher frame rates in thermography and infra-red viewing a line scanner with an indium antimonide detector and a rotating germanium prism has been designed. It produces heat images with 100 lines per frame on a television-type display tube at a flicker-free frame rate. The sweep efficiency of the scanning system is almost 100 per cent. The optical aberrations introduced by the scanning prism are analysed and found to be at a minimum when the refractive index lies between 3 and 4. Examples of heat pictures taken with different modes of operation are given.

MULTIPLE PULSE EMISSION FROM A HCN LASER

The time dependence of the output of a high-energy HCN laser has been studied with an indium antimonide detector. At a CH3CN partial pressure of 0.24 torr, three separate infrared pulses are emitted during a 250 μsec time interval after the current pulse. The addition of He, A, O2 or H2 changes both the number and delay between the pulses. As many as six pulses approximately 90 μsec apart in a 450 μsec period are observed with a He–CH3CN gas mixture.

High Resolution Study of Crystal Field Lines in the Far Infra‐Red

AbstractWe report the use of high resolution Fourier transform spectroscopy in the far infra‐red to study the lowest crystal field transitions in praseodymium ethyl sulphate and the double magnesium nitrates of cerium, praseodymium, neodymium, and samarium. The spectrometer employed is a Grubb Parsons Michelson interferometer with a Putley‐type indium antimonide detector at 2 °K. The observed line positions, intensities, and strengths are discussed in terms of conventional theories.

Synchronized High Speed Scanning Infrared Spectrometer

A spectrometer which scans a wavelength band of 0.6 micro in 30 microsec and is useful from 2-6 micro is described. The instrument can be synchronized with a pulsed source with a minimum triggering delay of 15microsec. The instrument is basically an Ebert spectrometer equipped with an indium antimonide detector at the exit slit, an aluminum scanning mirror placed 5 cm before the exit slit, and a wavelength calibration signal generator. The scanning mirror, which is supported on pivots inside a helical coil, deflects the spectrum through an angle of approximately 90 degrees onto the exit slit. When a capacitor is discharged through the coil, the resulting magnetic field spins the aluminum mirror causing the spectrum to move across the exit slit. The wavelength calibration signal generator produces a series of electrical pulses as the scanning mirror turns, permitting wavelength calibration when the pulses are displayed below the spectrometer signal on a dual beam oscilloscope. Using this instrument on a shock tube, data have bee obtained on the absolute spectral radiation intensity of air, nitrogen, neon, and argon heated by reflected shocks to equilibrium temperatures in the range of 6000 degrees K to 10,000 degrees K. In this temperature region with these gases, an important source of continuum radiation is neutral Bremsstrahlung caused by the inelastic scattering of electrons from neutral atoms and molecules. By employing the scanning ir spectrometer it has been possible to separate the continuum radiation from contributions owing to lines and bands and determine the cross section for the neutral Bremsstrahlung.