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Wyświetlanie 1-15 z 71
Tytuł:
Infrared Detectors - New Trends
Autorzy:
Piotrowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1872382.pdf
Data publikacji:
1995-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.-j
Opis:
Recent trends in infrared detectors are towards large, electronically addressed two-dimensional arrays and higher operating temperature. This will lead both to higher performance and to smaller, lighter and more affordable IR systems. Cooling requirements are the main obstacle to the more widespread use of infrared systems based on semiconductor photodetectors, particularly in the civil field. Fundamental limitations to performance of IR photodetectors are due to the statistical nature of generation-recombination processes and resulting noise. Ways to overcome the limitations are discussed including use of the optical immersion and optical resonant cavity. Finally, the progress in a mode of operation is presented, in which the thermal generation of carriers is suppressed by the use of stationary depletion of narrow gap semiconductors. The practical near room temperature narrow gap semiconductor photodetectors are reported. Competitive technologies based on Schottky barrier devices and low dimensional solids are considered briefly.
Źródło:
Acta Physica Polonica A; 1995, 87, 2; 303-316
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Inversion of Remote Sensing Data Using Multiple Ratios of Spectral Radiation Intensities and Neural Networks
Autorzy:
Cięszczyk, S.
Powiązania:
https://bibliotekanauki.pl/articles/1032310.pdf
Data publikacji:
2017-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
remote sensing
infrared spectrometers
infrared spectra
computer modelling and simulation
Opis:
The article presents a method for determining the content and temperature on the basis of spectra from remote measurements. The technique uses measurements of a high resolution radiation spectrum that allows the visibility of the individual rotational lines of gases such as CO₂, used here in the range of 2470-2495 cm¯¹. At the same time a new algorithm is applied of pre-processing the spectrum, involving the use of multiple ratios of intensity at several wavenumbers as input to an inverse model based on neural networks. Due to it, the dimensionality of the input can significantly be reduced. Additionally, the data interpreted do not have to be measured in units of spectral radiance. Thus only the calibration of the sensitivity of the spectrometer at various wavelengths is required. The neural models were constructed on the basis of data from the simulation. The proposed method works with a uniform layer of radiating gas for determining the temperature and CO₂ content. For a non-uniform layer it is possible to determine the line-of-sight temperature profile and average gas content. The method can be extended to different spectral ranges and to other gases present in substantial quantities in the exhaust gases of various processes.
Źródło:
Acta Physica Polonica A; 2017, 131, 6; 1454-1459
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared active phonons and optical band gap in multiferroic GdMnO₃ studied by infrared and UV-visible spectroscopy
Autorzy:
Bukhari, S.
Ahmad, J.
Powiązania:
https://bibliotekanauki.pl/articles/1075504.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
78.20.-e
72.20.-i
73.20.Mf
Opis:
Optical properties of multiferroic GdMnO₃ synthesized by sol-gel method have been investigated by measuring the infrared reflectivity and UV-visible absorption spectra. The infrared reflectivity spectrum of polycrystalline GdMnO₃ in the frequency range 30-7500 cm^{-1} at room temperature contains several phonon modes. The resonant frequency of observed infrared active phonon modes is found comparable with theoretically predicted results. Mean Born effective charges are calculated and discussed in view of the origin of ferroelectricity in GdMnO₃. Three strong absorption peaks observed in the UV-visible spectrum are attributed to the Mn (3d)-electron transitions. The optical band gap ≈1.2 eV is estimated from UV-visible absorption spectrum using Tauc's relation. GdMnO₃ seems to behave like an indirect gap semiconductor.
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 43-48
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Absorption on Shallow Donors in CdF$\text{}_{2}$
Autorzy:
Bednarek, S.
Adamowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1887164.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
Opis:
A theoretical description of shallow donor absorption spectra in CdF$\text{}_{2}$ in the infrared region is given. The properties of the stable (Y) and bistable (In) donors are analyzed and quantatively described. It is shown that the bistability of donors and the shape of the infrared absorption band have the same origin, which is the combined effect of electron-LO-phonon coupling, conduction band non-parabolicity and short-range central-cell potential.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 393-396
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Normal Incidence Mid-Infrared Photocurrent in AlGaN/GaN Quantum Well Infrared Photodetectors
Autorzy:
Sherliker, B.
Halsall, M. P.
Harrison, P.
Jovanović, V. D.
Indjin, D.
Ikonić, Z.
Parbrook, P. J.
Whitehead, M. A.
Wang, T.
Buckle, P. D.
Phillips, J.
Carder, D.
Powiązania:
https://bibliotekanauki.pl/articles/2041680.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
Opis:
We report the growth and characterization of AlGaN/GaN multiple quantum well structures designed to have intersubband transitions in the mid-infrared region of the spectrum. The samples were nominally undoped but were found to contain a high electron population in the wells induced by the local polarization fields. The sample was characterized by the use of the Raman spectroscopy and photocurrent spectroscopy. The Raman spectroscopy shows electronic Raman scattering from intersubband transitions in the AlGaN/GaN quantum wells. The e$\text{}_{1}$-e$\text{}_{2}$ and e$\text{}_{1}$-e$\text{}_{3}$ transitions of the confined 2d electron population in the wells can clearly be observed. A sample designed to absorb at 4μm was fabricated into mesa structures and the vertical photocurrent measured under normal incidence illumination from the free-electron laser FELIX. A wavelength and bias dependent photocurrent was observed in the mid-IR region of spectrum. The peak responsivity was of the order of 50μA/W at 4 K, the photocurrent still being measurable at room temperature.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 174-178
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Spectra of Retarded Molecular Oscillator
Autorzy:
Witkowski, A.
Henri-Rousseau, O.
Blaise, P.
Powiązania:
https://bibliotekanauki.pl/articles/1963248.pdf
Data publikacji:
1997-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.20.Ed
33.70.Jg
Opis:
Theoretical interpretation is proposed for the inhomogeneous broadening of the infrared line shapes of high harmonics of hydrogen containing modes observed by the optoacoustic and thermal lensing spectroscopy in the liquid phase of benzene and other organic transparent liquids. Attention is focused on the experimental fact that both line width and asymmetry factors of the harmonic series increase linearly with the harmonic number for which fact no satisfactory theoretical understanding was still available. This interpretation is based on recently proposed new approach to separation of electronic and nuclear movements accounting for the finite velocity of the π electronic cloud of vicinal molecules and its retardation in following the protonic motion. This retardation leads to the time dependence of molecular oscillator which may be viewed as anharmonic. The experimental results concerning the linear increase in the line width and the asymmetry factor with increasing order of the harmonic are well represented.
Źródło:
Acta Physica Polonica A; 1997, 91, 3; 495-504
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared-to-Visible Upconversion in Erbium Pentaphosphate
Autorzy:
Kaczmarek, F.
Balicki, M.
Karolczak, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929357.pdf
Data publikacji:
1993-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
78.55.Hx
Opis:
Infrared-to-visible upconversion has been observed by many authors in a variety of rare-earth-doped crystals. This paper reports the study of the up-conversion found in stoichiometric erbium pentaphosphate, ErP$\text{}_{5}$O$\text{}_{1}$4. Strong green fluorescence was observed upon pumping the crystal with a cw diode laser at a wavelength of about 800 nm.
Źródło:
Acta Physica Polonica A; 1993, 83, 6; 831-836
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Spectroscopy of Light Impurities in GaSb
Autorzy:
Kaczor, P.
Kaliński, Z.
Jakieła, R.
Powiązania:
https://bibliotekanauki.pl/articles/2043723.pdf
Data publikacji:
2005-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Eq
63.20.Pw
Opis:
In our work we study the doping behaviour of sulphur in Czochralski grown GaSb by means of the high resolution Fourier transform infrared spectroscopy and the secondary ion mass spectroscopy. We have revealed that the sulphur impurity forms an effective mass like donor state bound to the L-minimum of the conduction band. From the far infrared spectrum of this donor we derive the effective band masses of the L band minimum. We also observe local vibrational modes related to the arsenic and phosphorus isoelectronic impurities. From the nearest neighbour isotope splittings of these modes we conclude that the arsenic impurity occupies a tetrahedral substitutional site and the phosphorus impurity - a low symmetry lattice site.
Źródło:
Acta Physica Polonica A; 2005, 108, 4; 711-715
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coupling of Infrared Radiation to Intersubband Transitions in Tunneling Superlattices
Autorzy:
Nalewajko, C.
Załużny, M.
Powiązania:
https://bibliotekanauki.pl/articles/1991960.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
73.20.Dx
Opis:
The influence of the interference effects on the intersubband absorption line shape in weakly tunneling superlattices is discussed within the framework of nonlocal effective medium approximation.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 446-448
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Near-Infrared Tunable Reflection and Absorption Using Nanostructured Thin Film Structures Employing Phase-Change Material
Autorzy:
Ozdemir, A.
Kocer, H.
Powiązania:
https://bibliotekanauki.pl/articles/1398701.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Pt
Opis:
We present the design of a polarization-dependent tunable nanostructured thin film absorber in the near-infrared region. Germanium antimonide tellurite (GST) was employed as the phase change material in the designed structure. Our structure is composed of a periodic grating-type array of 150 nm thick Au buried with 50 nm thick GST layer from the top of the Au layer. The period of the gratings is 2 µm and in each period, GST width is 1 µm. GST was selected as the active phase change material because its optical properties undergo a substantial change during a structural transition from amorphous to crystalline phase. The optical absorption and reflection properties of the designed structure with respect to the geometric and material parameters were systematically investigated using the finite difference time domain computations. It was shown that absorption peak or reflection dip at the resonant wavelengths in the near-infrared region was red shifted from 2039 nm to 2143 nm wavelength by switching the phase change material from its amorphous to crystalline states. The distributions of the electric field and absorbed power at the resonant wavelengths with respect to different phases of the GST were investigated to further explain the physical origin of the absorption. Our study provides a path toward the realization of tunable infrared absorbers for applications, such as selective infrared emitters, infrared camouflage, sensors, and photovoltaic devices.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 464-467
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Absorption of Infrared Radiation by Electrons in Step Quantum Wells
Autorzy:
Załużny, M.
Nalewajko, C.
Powiązania:
https://bibliotekanauki.pl/articles/1876100.pdf
Data publikacji:
1995-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
73.20.Dx
Opis:
The influence of the depolarization effect on the spectral characteristics of intraband absorption on bound-free transitions in semiconductor quantum wells is analyzed using the local and nonlocal theories. The results obtained show that the local theory only qualitatively describes the modification of the bound-free absorption spectrum by the depolarization effect.
Źródło:
Acta Physica Polonica A; 1995, 87, 2; 449-452
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Reflection of $MnTe_2$ under High Pressure
Autorzy:
Mita, Y.
Ishida, Y.
Kobayashi, M.
Endo, S.
Powiązania:
https://bibliotekanauki.pl/articles/1813955.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
78.30.-j
Opis:
The IR reflection measurements of $MnTe_2$ were performed at room temperature under various pressures. It is observed that the reflectivity increases at the pressure range of 8-25 GPa and becomes almost constant at the higher pressure. The carrier concentrations obtained from the reflectivity spectra at the highest pressure region are the order of $10^{22} cm^{-3}$. Therefore it is concluded that pressure-induced semiconductor-metal transition occurs at the pressure range of 8-25 GPa.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 617-620
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Detectors for the Future
Autorzy:
Rogalski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1807754.pdf
Data publikacji:
2009-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.79.Pw
07.57.Kp
73.21.Cd
78.67.Pt
79.60.Jv
Opis:
In the paper, fundamental and technological issues associated with the development and exploitation of the most advanced infrared detector technologies are discussed. In this class of detectors both photon and thermal detectors are considered. Special attention is directed to HgCdTe ternary alloys on silicon, type-II superlattices, uncooled thermal bolometers, and novel uncooled micromechanical cantilever detectors. Despite serious competition from alternative technologies and slower progress than expected, HgCdTe is unlikely to be seriously challenged for high-performance applications, applications requiring multispectral capability and fast response. However, the nonuniformity is a serious problem in the case of LWIR and VLWIR HgCdTe detectors. In this context, it is predicted that type-II superlattice system seems to be an alternative to HgCdTe in long wavelength spectral region. In well established uncooled imaging, $VO_x$ microbolometer arrays are clearly the most used technology. In spite of successful commercialization of uncooled microbolometers, the infrared community is still searching for a platform for thermal imagers that combine affordability, convenience of operation, and excellent performance. Recent advances in microelectromechanical systems have led to the development of uncooled IR detectors operating as micromechanical thermal detectors. Between them the most important are biomaterial microcantilevers.
Źródło:
Acta Physica Polonica A; 2009, 116, 3; 389-406
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Absorption of Multiple Quantum Wells: Bound to Continuum Transitions
Autorzy:
Oszwałdowski, R.
Jaskólski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1992054.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
78.66.-w
85.30.Vw
Opis:
Optical transitions between bound and continuum states in multiple-heterojunction quantum structures are numerically investigated. In the conduction band energy range the absorption to continuum is studied within one-band effective-mass approximation. By changing the shape of quantum wells, we can tune the energy corresponding to absorption peak. We also show how the absorption is modified in the case of annealed structures. The inter-subband transitions in the energy range of valence band in Si/Si$\text{}_{1-x}$Ge$\text{}_{x}$/Si quantum well are described with the help of multiband Luttinger-Kohn Hamiltonian. Particular attention is paid to transitions to resonant states.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 473-478
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Phonons in HgCdMnTe Using Far-Infrared Reflectivity
Autorzy:
Dudziak, E.
Bożym, J.
Pruchnik, D.
Baran, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929684.pdf
Data publikacji:
1993-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
71.45.Gm
Opis:
The first reflectivity spectra of Hg$\text{}_{1-x-y}$Cd$\text{}_{x}$Mn$\text{}_{y}$Te with 0.03 < x < 0.1 and 0 < y < 0.05 were measured in the spectral region 700-30 cm$\text{}^{-1}$ at 300 K and 90 K. The quaternary alloys measured show three mode behaviour. The experimental results are interpreted by using a classical dynamic dielectric function model.
Źródło:
Acta Physica Polonica A; 1993, 84, 3; 595-598
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 71

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