Contributed papers
In the paper the results of analysis of some data gathered by three independent Data Acquisition Systems, during prolonged outdoor testing of several commercial photovoltaic modules (PV modules) working in Solar Lab of Wroclaw University of Technology and University of Opole, are presented and discussed. The effects of solar radiation intensity, ambient temperature, and even wind rate and direction on the actual performance of standard silicon solar cells based PV modules are shown. Special emphasis has been put on potentially cumulated electric charge and energy generated by the modules in different ambient conditions rather than on standard parameters measured. Effect of single-axis sun-tracking is demonstrated showing that in poor insolation conditions using of such systems may be nonbeneficial.
The rigorous optical model of diode lasers has been used to investigate an impact of various construction details of multi-quantum-well nitride lasers, as the number of quantum wells placed in active region, as well as designs of their waveguides and buffer layers located between the substrate and the laser structure, on room-temperature laser operation. The model is used to discuss some possible structure modifications to reduce lasing thresholds. Recommended design parameters have been found for each structure.
Military optoelectronic systems proved their great usefulness at night or poor atmospheric conditions during recent conflicts. However, to assure high effectiveness of these sophisticated systems, they must be regularly tested. Due to secrecy of some military optoelectronic systems, limited availability of military standards, and numerous but inconsistent literature there is significant confusion in the area of military optoelectronic metrology. A review of typical testing methods of the three basic groups of optoelectronic systems (missiles guided using optoelectronic methods, optoelectronic imaging systems, and optoelectronic countermeasures) used in modern military armament is presented in this paper.
This paper presents an analysis of the recently reported
data of Yoshino et. al. [1,2] on p+-n HgCdTe diodes with a view to verify
quantitatively the previously reported relationship between deep levels
and RoA product of the diodes. The result of this analysis suggests that
the trap level, located below 6 meV from the bottom of the conduction band
edge, contributes to the trap assisted tunnelling currents in the medium
reverse bias region. Also there is evidence that zero bias resistance area
product is limited by the ohmic surface leakage and generation-recombination
contributions. The observed current-voltage (I–V) characteristics and dynamic
resistance-voltage (Rd–V) characteristics have been shown to excellently
fit the theory by taking into account the contributions due to: (i) thermal
diffusion of minority carrier from the neutral regions, (ii) generation–recombination
(g-r) current in the depletion region, (iii) trap assisted tunnelling (TAT)
currents due to a trap level located at 6 meV below the bottom of the conduction
band edge, (iv) band to band tunnelling (BTB) currents, and (v) ohmic component
of surface leakage currents.
Though the RoA product of the diodes is shown to be limited
by g-r and surface concentrations, the variation in RoA product of the
diodes is interpreted as arising due to the variation in planar area of
the diodes accompanied with the varying surface contributions, since g-r
contribution should remain constant for all diodes.
Mercury-cadmium-telluride (MCT) 2?64 linear arrays with
silicon readouts were designed, manufactured and tested. NCT layers were
grown by MBE method on (103) GaAs substrates with CdZnTe buffer layers.
50?50 ?m n-p-type photodiodes were formed by boron implantation.
The parameters of long wavelength infrared MCT linear
arrays with cutoff wavelength ?co ?10.0–12.2 ?m and Si readouts were tested
separately before hybridisation. The HgCdTe arrays and Si readouts were
hybridised by cold welding In bumps technology.
Dark carrier transport mechanisms in these diodes were
calculated and compared with experimental data. Two major current mechanisms
were included into the current balance equations: trap-assisted tunnelling
and Shockley-Reed-Hall generation-recombination processes via a defect
trap level in the gap. Other current mechanisms (band-to-band tunnelling,
bulk diffusion) were taken into account as additive contributions. Tunnelling
rate characteristics were calculated within k?p approximation with the
constant barrier electric field. Good agreement with experimental data
was obtained.
The authors present the medical, physical, and technical background for the new method of near infrared transillumination – back scattering. The method, for the first time ever, allows for almost complete elimination of the influence of the alterations in skin circulation on the optical signal iDS(t) subtly modulated by the changes in the width of the subarachnoid space (SAS). This has been accomplished through division of the distal or deep optical signal iDS(t) over the optical reference signal iPS(t) which is independent of the width of SAS, but depends on the propagation in the other tissue layers in the same manner as iDS(t). From the obtained quotient, a weak component was extracted that depends on the cerebrovascular pulsation. Described in this paper is the mathematical method of reducing the influence of the changes in skin blood flow on the transillumination signals. A tilt test was used as an example to show the capacity of the method to determine the cerebro-spinal reserve volume.
The authors describe the application of the newly designed method of near-infrared transillumination-back scattering in monitoring of the instantaneous width of the subarachnoid space. Description is provided with the method of elimination of influence of blood circulation in the scalp on the signals recorded from individual sensors. This influence has been eliminated through application of two sensors located at different distances from the source of radiation. The quotient of the intensities of radiation received by the sensors – distal over proximal – referred to as the transillumination quotient, contains information on propagation of infrared radiation within the subarachnoid space. Mathematical background of this solution has been given. The method of near-infrared transillumination-back scattering allows for continuous non-invasive assessment of cerebrovascular pulsation through its direct effect – pulsatile changes in the width of the subarachnoid space. The authors present examples of recordings obtained in healthy volunteers.
The subject of this work is a novel fibre optic distributed sensor system. The system uses a technique called multiplexed reflectometric interferometry to measure dynamic strain in a network of single mode optical fibre sensors. The sensor is constructed on an unbalanced fibre optic Michelson’s interferometer. This article presents influence of the wavelength change of radiation source on the course of interference contrast function of the unbalanced Michelson’s interferometer. A digital demodulation with application of a fibre optic coupler 3?3 is also presented. The maximum number of individual sensors is currently limited by the optical power budget and will increase with new technology implementation. The system can address a variety of sensor types for different physical parameters.
A nonconventional hollow cathode discharge (HCD) modification grounded on a conical bottom (CB) cylindrical cathode is reported. This CBHCD enhances the main HCD property, i.e., the sputtering of the cathode surface/probe inserted. Comparative polarisation measurements with a conventional flat bottom HCD show a stronger narrowing of the Hanle signal width for the sputtered Cu atoms in CBHCD. Thus their density is higher in CBHCD. This result is specified by the radial optogalvanic profile. It contains two peaks of the mentioned density, i.e., near the cylindrical cathode surface and over the cone peak. Some preliminary examinations of CBHCD as an ion source in three arrangements are performed and discussed.
A compact device for measurements of levitated particles in humid atmosphere up to 100% relative humidity and in temperature range from –30 to 600C was built. The preliminary experiments were done using ethanediol and water microdroplets. Light scattered by the trapped particles on two perpendicular polarisations was recorded. On the basis of Mie theory information on the radius and refractive index of the droplets was extracted with FFT and T-matrix method combined with fitting procedure.
The electrical conductance of a-Si:H is studied in films deposited on ion-exchanged optical waveguides in glass substrates. The effect of chemical composition of the near-surface region of the waveguide is considered from the viewpoint of the electrical instability of a-Si:H related with the penetration of Na ions from the substrate into the film. The optical waveguides have been prepared by Ag+-Na+ or K+-Na+ thermal or field-assisted ion exchange in soda-lime glass (SLG). The Na concentration in the near-surface region of the glass substrate has been established by means of elastic recoil detection analysis (ERDA). The obtained results demonstrate the possibility of reduction of electrical instability of a-Si:H films deposited on optical waveguides in glass. It is shown that in some cases an additional Na depletion of the near-surface region is necessary to avoid Na contamination of the a-Si:H films.