HgCdTe infrared detectors have been intensively developed over the past forty years since the first synthesis of this compound semiconductor in 1958. Today, HgCdTe is the most widely used infrared detector material. This paper reviews key developments in the crystal growth and device history of this important technology. Projections and challenges for the continued evolution of this technology are summarized.
Keywords: HgCdTe single crystals and epitaxial layers, HgCdTe photoconductors and photodiodes, focal plane arrays.
Authors present new aspects of recently published non-invasive method of near-infrared transillumination/back scattering (NIR-T/BS) in its application for recording of changes in instantaneous width of the subarachnoid space (SAS), as source of information on the amplitude of cerebrovascular pulsation in subsequent phases of the cardiac cycle. For confirmation of the credibility of the recording as carrying information on the changes within the SAS, recordings were also performed after non-invasive elimination of skin circulation in the sensor area with skin compression. It was proved that the pulsation recorded with this technique is really of intracranial origin, regardless of the blood flow in the skin of the frontal region.
Keywords: transillumination, subarachnoid space, cardiac cycle.
A novel idea of optical fibre laser Doppler velocimetry
especially useful for non-contact testing of rotation elements is presented.
The main idea of the system is based on an application of interferometric
measurement of Doppler effect by a specially constructed optical fibre
interferometer. The standard single-mode coupler, connected with laser
diode operated at 0.68 µm, has been used as the main optical element.
A suitable selection of a target distance from the specially constructed
optical head makes the system work as a single-reflection Fabry-Perot fibre
interferometer. Such device provided polarisation
stability as well as good environmental shielding. The
special numerical processing of interferometric output signals by a technique
based on FFT gives a possibility of rotation element testing. The theoretical
investigation was compared with experimental data obtained for the commercially
available magnetic hard disc and the dynamically tuned electromechanical
gyro.
Keywords: optical fibre interferometry, laser Doppler velocimetry, vibrometer.
In this paper, the results of the experimental investigation of electroluminescent phenomena are presented. The electroluminescent effect is observed in some composite semiconductors, among others – ZnS, doped by Mn and Cu. The concentrations of impurities in good quality electrophosphores are higher than in photoluminophores and they are within the range of 10–4–10–3 g/g. The worked out electroluminophors were tested in the electric field of sinusoidally changeable intensity. The influence of electric field both on spectral characteristics and electroluminescence intensity was examined. The final aim of the tests is elaboration of electric intensity sensors which will be applied in monitoring of operation of electromagnetic power arrangements in the future.
Keywords: optical fibre sensors, electroluminescence, electric field measurements.
The in-line fibre-optic polarisation analyser enabling measurement of full polarisation parameters of light propagated in optical fibre is presented in the paper. This device uses a standard single-mode optical fibre in a system of the polarimetric configuration. Introduction of controlled birefringence in such a fibre and application of an appropriate polariser set at the end of the system allow to get full information about polarisation parameters to obtain. Evaluation of any changes of the state as well as the degree of polarisation have been achieved by application of an appropriate detection system and numerical calculation based on the coherence matrix theory. Finally, some experimental results of the system performance and determination of the main errors are presented.
Keywords: fibre-optic sensor, polarimeter, state and degree of polarisation.
The paper describes principles of minimisation of noise produced in infrared detection systems. Analysis of operating conditions affecting signal to noise ratio (S/N) has been carried out. Also analyses for maximisation of S/N in advanced methods of optical signals detection have been made. Many practical solutions have confirmed theoretical predictions.
Keywords: infrared detectors, low-noise preamplifier, thermal imaging systems, non-contact thermometers.
In the light of recent advances in subwavelength optics,
the development of optical nanodevices is nowadays conceivable. Among the
best candidates to act as the elementary components of such devices are
nanoscale structures of noble metals. These materials are capable to sustain
resonant electron oscillations (plasmons). This phenomenon gives rise to
a spectrally selective optical response and a local field enhancement which
can be used in the context of nano-optics. Furthermore, it allows to transduce
the optical signals into electrical ones (and vice versa). Here, we demonstrate
an optical nanodevice
based on plasmon resonances in gold nanostructures. The
adequate metal structures were produced by electron-beam-lithography. The
basic operating functions of the device, namely signal processing on the
nanoscale and its interfacing on the microscale, were experimentally observed
in the optical near-field by photon scanning tunneling microscopy. Furthermore,
as a numerical method for validation of the near-field observations the
Green’s Dyadic Technique is pointed out.
Keywords: surface plasmons, noble metals, nanoparticles, nanowires, photonics, optoelectronics, nanodevices.