We have investigated the reflectance of crystalline silicon and germanium samples for infrared radiation polarized parallel and perpendicular to the plane of incidence. A Fourier transform infrared (FT-IR) spectrometer was employed to measure the specular reflectance at angles of incidence from 20° to 60° in the wavelength range between 2 μm and 25 μm. The measurements agree with the theoretical analysis to within the experimental uncertainty. At large angles of incidence, the reflectance depends strongly on polarization. Since the beam in a spectrometer generally exhibits partial polarization, the measured reflectance without a polarizer may differ from the average reflectance for the two polarization states. This work demonstrates that silicon and germanium can be used as standard reference materials for specular reflectance in the mid-infrared region.
An automated long wavelength (submillimetre) telescope simulator is described which produces a diffraction limited image in the simulator focal plane for laboratory measurement of the matching of receivers of photometers to the telescope being simulated.
The results of systematic measurements of specular reflectances of both single as well as double surface polished silicon and germanium at glancing angles of incidence from 10° to 70° in the infrared (IR) region of 2.5–25 μm have been discussed. The experimental results have been explained by comparison with the theoretical reflectance data obtained using Fresnel's theory.
The responsivity expression of a pyroelectric detector with a surrounding substrate is given. The calculation of the responsivity in this case is compared with that for a suspended case. The effect of the surrounding substrate cannot be neglected for small r1f12, where r1 is the radius of the electrode and f is the frequency.
Optothermal CO2 laser spectroscopy of air polluted by CO2 and SO2 has been performed with improved selectivity in the low pressure range. The ability of kinetic cooling effects to give additional improvement of the detection selectivity is demonstrated.
In many academic disciplines, including psychology, sociology, and management studies, there is broad interest in gender issues. But does this hold true for the literature on key account management, global account management, or strategic account management? Anecdotal evidence suggests that key account management, in practice, is still a rather male domain. Is this reflected in extant research, either through a discussion of the role of female key account managers or through the absence of such a discussion? This study first presents a systematic literature review of the key account management literature regarding research on gender issues. The results show that academic interest in gender issues in key account management has been very limited. It then argues for the necessity for increased scholarly research into gender issues in key account management and it develops numerous avenues for future research along the lines of (1) actors, (2) activities, and (3) resources in key account management as well as (4) relationship atmosphere and the environment in which key account management relationship are being managed.
LiTaO3 type II pyroelectric detectors have been prepared and measured. The responsivity Rv(500 K, 10 Hz) = 110 V/W; detectivity D∗ (500 K, 10 Hz) = 6.15 × 106 cmHz12/W. The mechanism of the detectors is discussed.
Dual epilayer structures consisting of p−p+ on p− silicon substrates were characterized using non-destructive Fourier transform infrared reflectance spectroscopy and sheet resistance measurements. The thickness of each layer, as well as the dopant concentration of the layers were determined. Results were compared to data obtained by spreading resistance profiling.
Using controlled feedback and coincident far infrared absorption, we have shown that the superradiant emission process in NH3 pumped by the 9R16 line of a CO2 TEA laser has a marked effect on the absorption of laser energy and vibrational heating of the gas. Since many polyatomic molecules pumped by IR laser are efficient superradiant far infrared sources, the effect is important for laser induced fluorescence studies in these polyatomics.
Infrared spectra of lanthanum sulphate nonahydrate are studied over the 4000–50 cm−1 range. The bands pertaining to different internal and external modes of sulphate ion and water molecules are observed and assigned. It is shown that coordinated water molecules exist at two site symmetries C1 and Ci, which provides confirmation of crystallographic data. Lattice water is not found in these crystals. The effect of low temperature on librational modes of coordinated water and their lattice vibrations are studied in the 550–50 cm−1 region. The potential force field constants are calculated for rocking, wagging and twisting librational modes of water at 290 K, 80 K and 60 K. The higher value of the potential constant for the rocking mode from the wagging librational mode shows the in-plane bend of the hydrogen bond in lanthanum sulphate crystals.
This paper presents a mathematical model of the apparatus channel of an infrared remote sensing radiometric system. The latter comprises: (1) the sounded object. This may be a medium, such as a cloud or a dense aerosol layer caused by a temperature inversion; (2) background radiation; (3) the atmospheric channel, or the medium where the signal radiation from the sounded object and the background radiations propagate; (4) the apparatus channel or the infrared radiometer itself. The system described is useful for investigating, measuring or controlling objects and media. The apparatus channel modelled is proposed as a lock-in detector. The joint action of all types of noise due to the stochastic nature of the infrared radiation or to the optoelectronic and electronic conversions is discussed. The final results allow calculation of the apparatus channel output signal-to-noise ratio.
We report on n-InSb photoconductive detectors, which are either mounted on different substrates (metals and synthetic materials) or embedded in a special glue. If these detectors are cooled to 4.2 K, the different coefficients of expansion provide either a uniaxial or a hydrostatic pressure. This pressure causes a shift of the resonances (for the mounted detectors up to 5.5%, for the embedded detector 5.8% at 2.3 T) and a freeze out of electrons, which results in a decrease of the cyclotron resonance (CR) signal in comparison to the impurity cyclotron resonance (ICR) signal for the embedded detector.
Optical properties of Hg1−xCdxTe are summarized in this study. Based on Penn-like models, the Moss relation and the Wemple and DiDomenico approach, calculations of energy gap, plasmon energy, Fermi energy, oscillator strength and electronic polarizability have been made. Comparisons are made with the data available in the literature. Details of the dependency of the properties on composition are presented.
The specific detectivity of pyroelectric sensors at low frequencies is mainly influenced by the thermal conditions within the sensor. The temperature noise caused by heat exchange between the sensitive element and its surroundings is transformed into an increase of the dielectric loss due to electrothermal coupling. The complex normalized current responsivity is used to calculate the influence of thermal conditions. While the absolute value ¦TR¦ gives the frequency response of the sensitivity, the additional dielectric loss tan δT is deduced from the imaginary part. The loss due to electrothermal coupling tan δT exceeds the dielectric intrinsic loss tan δi for most sensor structures within the frequency range up to 100 Hz. Thus, the maximum attainable specific detectivity of a pyroelectric sensor at normal operation frequencies is dependent on its construction rather than on the material parameter dielectric intrinsic loss tan δi which is frequently referred to. The effect of electrothermal coupling can be employed in sensors with reduced sensitivity at low frequencies as used for FTIR-devices.
A spatially-scanning phase-sensitive heterodyne far-infrared (FIR) polarimeter/interferometer for measurement of plasma current and electron densities is described. The instrument utilizes a rotating diffraction grating wheel for the dual purpose of spatially scanning the plasma cross section and providing a Doppler frequency offset for heterodyne detection purposes. Only two detectors are required to obtain accurate interferometric and polarimetric information for 15 discrete spatial chords. A novel approach to the optical processing of the initially linearly polarized probe beam allows the Faraday rotation of the vibrational ellipse to be unambiguously encoded as a phase modulation on the intermediate frequency carrier signals extracted from the two detectors. The plasma birefringence can be recovered from the corresponding amplitude modulation.
Spectrally resolved data for the real part, n(λ) of the complex refractive index, n̂ = n +ik, of bromoform (tribromomethane, CHBr3) at room temperature (298 K) in the wavelength range 1–13 μm are presented. The measurements were made using the near-normal reflectance technique. The accuracy of the method was confirmed by comparing measured values of n(λ) of water with available data in the literature. For bromoform, n(λ) is found to decrease gradually from 1.58 to 1.51 over this wavelength range, except in the region of anomalous dispersion near absorption bands at 3.3 and 8.7 μm. A complete infrared window for extinction measurements on suspended particulates can be obtained using CCl4 in the spectral range 1–6 μm, CHBr3 in the ranges 6.0–7.4 μm and 11–13 μm, and CS2 in the range 7.4–11.0 μm. The data for n(λ) of CCl4 in the range 1–9 μm, and those for CS2 in the range 7.4–11.0 μm, obtained from reflectance measurements, compare favorably with data available in the literature.
Variations of energy gap (Eg) and refractive index (n) with the concentration have been studied through a set of simple empirical equations proposed in the case of certain mixed crystals of technological importance. Similarly, another set of equations has been proposed to explain the temperature dependence of the energy gap in semiconductors such as GaS, GaSe, GaTe, SnS2 and SnSe2. The results obtained in both cases are found to be in excellent agreement with the experimental values. The proposed equations are proved to be simple and advantageous over others in the sense that less computational work is involved in the calculations of Eg and n.
Lead telluride epilayers and p-n junctions were grown on silicon substrates by hot wall epitaxy in order to construct monolithic infrared (IR) detectors arrays, using II-a fluorides as buffer layers. Schottky barriers were also made in the same epilayers to compare the figures of merit. The p-n junctions had performances comparable with the metal barriers and both devices had noise sources in addition to the expected thermal and background ones.
A novel design for a surface relief grating with rectangular grooves is presented. The first reflected diffraction order shows experimentally 84% diffraction efficiency for a metallic grating. The required binary surface relief can be manufactured by using one single microlithographic fabrication step similar to standard processes in microelectronics. Each period of the grating consists of a subwavelength “minilattice” with a variable duty cycle. A theoretical model of the structure is presented and compared to measurements at 10.6 μm wavelength. Applications ranging from deflectors, polarizing beam splitters, variable attenuators to general diffractive components such as kinoforms for laser beam shaping are proposed.
