Filter-radiometer-based realization of candela and establishment of photometric scale at UME

The luminous intensity unit of candela was realized based on filter-radiometer, which is traceable to detector-based primary standard electrical substitution cryogenic radiometer (ESCR). In that realization the traditional Osram Wi41/G-type incandescent lamp and filter-radiometer consisting of an aperture, a V(λ) filter and a silicon photodiode based trap detector were used as light source and detection element, respectively. Measurement techniques of effective aperture area, spectral transmittance of V(λ) filter and absolute responsivity of trap detector are also presented.     

Relaxor properties of Fe-doped TlInS<Subscript>2</Subscript>

The relaxor properties of Fe-doped TlInS₂ crystals are investigated. It is shown that Fe-doped TlInS₂ compounds exhibit all features inherent in relaxor ferroelectric materials. The temperature range of existence of the microdomain (relaxor) state and the temperature of the transition from this state to a macro-domain state are determined.     

Circular groove shaped resonator for millimeter waves

In millimeter wave lengths region semiconductor generators, amplifiers, mixers and other solid state UHF devices find a wide application. In our work, we suggested to use aCircular Through-Shaped Resonator for obtaining power combination using active elements at frequency region f20–40 GHz.The resonator is formed by two plane aluminum reflectors. The first reflector has a circular groove. The second reflector has coupling elements. The first and the second reflectors are considered as a ring groove shaped waveguide.A resonator spectrum was calculated and analyzed in the frequency range f 20–40 GHz. It is showed that, in the given frequency range the resonator spectrum has a complicated structure and is formed by a series of spectrum lines; a frequency range between the series increases with the frequency increasing.We studied on transmission coefficient of the resonator, frequency shifts of spectrum lines when inserting a thin (t/0.003) dielectric substrates into the resonator, and also attenuation constants of waves propagating in circular groove (due to losses in metal).     

Purification of low-paraffinous oil fractions using the two-phase extracting system ionic liquid + supercritical carbon dioxide

Use of the two-phase extracting system ionic liquid (IL)—supercritical CO₂ for selective purification of medium-viscosity oil fractions from a mixture of low-paraffinous Azerbaijan crude oils results in a three- to sixfold reduction of selective solvent (IL) consumption. The use of such a two-phase system allows one to decrease the temperature (from 80 to 31°C) and the duration of the process.     

Dependence of the Energy Resolution of a Hemispherical Semiconductor Detector on the Bias Voltage

It is shown that the series expansion of the amplitude and variance of the hemispherical semiconductor detector signal in inverse bias voltage allows finding the Fano factor, the product of electron lifetime and mobility, the degree of inhomogeneity of the trap density in the semiconductor material, and the relative variance of the electronic channel gain. An important advantage of the proposed method is that it is independent of the electronic channel gain and noise.     

Cryogenic radiometer based absolute spectral power responsivity calibration of integrating sphere radiometer to be used in power measurements at optical fiber communication wavelengths

This paper covers the absolute spectral power responsivity calibration of spectralon-coated Integrating Sphere Radiometer (ISR) equipped with 3 mm diameter InGaAs photodiode to be used as a transfer standard in fiber optic power measurements against Electrical Substitution Cryogenic Radiometer (ESCR) in Optics Laboratory of National Metrology Institute (TUBITAK UME) of Turkey. The initial uncertainty arising from the use of the Electrically Calibrated Pyroelectric Radiometer (ECPR) as a transfer standard in radiometric scale is 0.5% (k=2), which particularly comes from irregularity in the surface homogeneity of ECPR. In order to eliminate the ECPR step as well as its initial uncertainty contribution in fiber optic power measurements, the calibration application herein was carried out. Moreover power stabilization measurements of DFB laser sources at both 1309.1 nm and 1549.0 nm, the beam size determinations, and spectral analyses of these laser sources as well as spatial and angular dependence of spectral responsivities of the ISR were presented in this paper. The total expanded uncertainties were calculated as 0.283% and 0.315% in the determination of absolute spectral power responsivities of the ISR for 1309.1 nm and 1549.0 nm wavelengths respectively (k=2).     

Photoconductivity in the Ternary Layered Semiconductors

Spectral dependences of the photoconductivity, near-band-edge absorption were studiet at room and low temperatures for a number of TlInS2 and TlInSl2 type layered ternary chalcogenides. Some peculiarities in the temperature dependences of the spectral properties are assigned as due to a low temperature phase transition to an incommensurate and ferroelectric state. Temperature coefficients of the band gap for TlInSe2 are determined. Spectral properties of TlInS2 doped with Nd and Yb are also presented and discussed. It is shown that the long-wave lenght absorption edge of TlInS2 crystal obeys the Urbach's rule. High photosensitivity in the visible and near IR range of spectra makes these materials attractive for optoelectornics application.     

Relaxor properties and the mechanism of conduction in TlInS<Subscript>2</Subscript> crystals exposed to gamma irradiation

The density of states at the energy levels associated with radiation-induced defects, the localization length of a defect center, and the hopping distance of charge carriers are determined in a TlInS₂ crystal. It is demonstrated that, by varying the dose of gamma irradiation, it is possible to control the dielectric properties of ferroelectrics and to attain a stable relaxor state. In the temperature range of existence of this state, charge carriers execute tunneling from electron levels in the band gap through potential barriers created by an incommensurate superstructure of the TlInS₂ crystal.     

Theoretical Approach to Energy Resolution of Semiconductor Detectors

All processes occurring in semiconductor detectors during detection of primary monoenergetic particles lead to broadening of spectral lines. In this work, a general expression for the energy resolution of semiconductor detectors is obtained using the theory of branching cascade processes. It is shown that the general formula involves all contributions to the spectral line broadening described in the literature and additional contributions associated with fluctuations of electron and hole lifetimes caused by inhomogeneity of traps in the semiconductor material and fluctuations of the electronic channel gain.