Showing papers on "Responsivity published in 1974"

Influence of Black Coatings on Pyroelectric Detectors

Abstract: The extent to which the thermal capacitance and resistance of a black coating on a pyroelectric detector offset the gain in optical absorptance is investigated. A black paint is shown to be of little value, but a coating of gold-black may increase the detector responsivity for modulation frequencies up to at least several kilohertz. When a coated pyroelectric detector is calibrated electrically, a correction is necessary for the thermal impedance of the black. For gold-blacks of superficial density 2 g m(-2), this correction is shown to be less than 2% for frequencies within the 0-100-Hz range.

Effects of poling conditions on responsivity and uniformity of polarization of PVF2 pyroelectric detectors

Abstract: A large number of pyroelectric detectors, fabricated from commercially available PVF2 and poled under a variety of conditions of voltage, temperature, and time have been evaluated for responsivity and uniformity of polarization in the direction of the poling field. Results show that uniformity of polarization (a requirement for flat frequency response) can be achieved and responsivities as high as 2.9 μA/W can be obtained.

Optimization of millimeter-wave glow-discharge detectors

Abstract: A simplified theory that provides the basis for determining the optimum gas composition and pressure which maximize the responsivity of millimeter and submillimeter glow-discharge detectors at a given spectral frequency is presented together with experimental verification.

Infrared laser interferometer for measuring air-bearing separation

Abstract: The design and characteristics are presented for an infrared instrument capable of measuring air-bearing separation distances over a mechanical bandwidth ranging from dc to 30 kHz. The measurement technique involves monitoring optical intensity variations of the interferometric cavity formed by two air-bearing surfaces. This intensity varies between a minimum at zero separation and a maximum at a distance equal to one-quarter of the optical wavelength. For air-bearing distances less than 1 µm, a convenient source is the 3.391 µm infrared line of the helium-neon laser. By continually monitoring a fraction of the intensity of the optical source, a real-time analog division can be performed on the spacing signals to produce an output independent of laser intensity variations. Room-temperature indium arsenide detectors were selected for their high responsivity and rapid rise time.

Characteristics of gallium doped silicon infrared detectors

Abstract: Interest in extrinsic doped silicon infrared detectors for operation in the mid-infrared (i. e., 3- to 5-µm spectral band) has recently been growing because of the benefits provided by employing silicon technology. The photo-ionization cross section of Si:In operated at temperatures greater than 77°K has been previously measured. This paper presents data on the signal-to-noise ratios (SNR) at temperatures from 4° to 70°K under two conditions of background photon flux density and detector bias. This data was taken from a specimen with an indium doping of 2.7 × 1017 cm−3, Quantum efficiencies of 50 percent were measured. Detectivity, D*, as a function of temperature decreased by about 10 percent at 55°K and was even less at 70°K. Mobility data in conjunction with the measured responsivity data is used to determine the hole lifetime. It has been found that this lifetime increases as the temperature increases. Lucovsky(1) has presented a model of the spectral response expected because of deep impurity levels. The measured spectral response data is in quite good agreement with that predicted by theory.

High Performance, Wide Bandwidth (Hg, Cd)Te Detectors

Abstract: The frequency dependence of responsivity and detector noise for (Hg,Cd)Te detectors operating in the 8-14 pm region at 77°K was investigated. The results showed that these quantities have the same frequency dependence and corner frequency. Values of f* were thus experimentally determined and found to be >10 MHz for detectors that have D*X - 5 X 1010 cm Hz% Watt-1. The results are shown to be consistent with a simple photoconductive theory based on the assumption of equal lifetimes for holes and electrons.

DC responsivity of proximity effect bridges to high frequency radiation

Abstract: The effect of microwave radiation on the dc current-voltage characteristic of proximity effect bridges has been studied at frequencies of 10, 35, and 90 GHz. The properties of bridges fabricated in layered films of Nb and Ta are reported. The fraction, epsilon, of the incident radiant power absorbed by the bridge is measured calorimetrically, permitting determination of the intrinsic responsivity (volts per watt of power absorbed when operated in a current-biased mode). In the test geometry employed, epsilon is typically about .0001 for a 0.1 ohm Nb-Ta bridge, and increases roughly linearly with dc junction resistance. Broad-band responsivity is generally independent of incident power, increases with increasing critical current (decreasing temperature), and decreases with increasing frequency. Peak responsivities achieved to date are about 100,000 V/W (absorbed) at 10 GHz and about 100 V/W (absorbed) at 90 GHz.

Responsivity of photocathodes.

Abstract: The responsivity of photocathodes and the gain of photoelectronic imaging devices are generally measured with a tungsten lamp operating at 2854 K. Measurements are then given in a form that includes photometric units. For instance, responsivity of a typical S-20 photocathode is 150 × 1 0 6 A/lm, and responsivity of the S-20VR photocathode is 400 × 1 0 6 A/lm. Often natural illumination is also expressed in photometric units. For instance, a clear moonless night corresponds to an illumination of about 1 0 3 lux, and a full moonlit night corresponds to about 10 1 lux. The hazards associated with the use of photometric units in such measurements were pointed out by Biberman. Nevertheless, the performances of photoelectronic imaging devices are often calculated using natural field illumination values and responsivity and gain characteristics as measured with a tungsten lamp at 2854 K, all the data involving photometric units. Some techniques have been introduced to reconcile measurements obtained with different sources and different receivers.A large number of spectral matching factors were calculated. The published results may not apply directly to relatively complex spectral distribution such as the night airglow. For many cases of importance, new sets of values of the spectral matching factor, α, would have to be calculated. In the case of blackbody ra­ diators, for instance, sets of values of α may have to be calculated for a wide number of temperatures, T. It would be desirable to have data related to the most com­ mon photosurfaces, noted here with the index i, and in a form easily applicable to the calculation of photocathode responsivities, Si. There is also a need to check the cor­ relation between photocathode responses to tungsten lamp sources and to natural illuminations. This letter compares the variation of responsivity of three types of photocathodes S-20 with different extended red response as a function of illumination sources. These variations are shown in graphs that give the responsivity of the photosurface to the blackbody radiators directly. The correspondence between tungsten lamp illumination and night airglow is also given_for different photocathodes. The average responsivity St of a photocathode, i, is given by