The new model of incoherent-to-coherent infrared (IR) image converter based
on a GaAs photoconductor joined to an electro-optic (EO)
Bi12SiO20 crystal has been analysed theoretically and experimentally. The
possibility of field transfer from the photoconductor to the EO crystal
under the IR radiation sufficient for realization of the EO
(Pockels) effect in the EO crystal was assessed. Based on the electric field
parameters and the parameters of the photoconductor and EO crystal, the
threshold sensitivity of the converter was estimated. The experimental
photoconductor-EO crystal structure by which IR radiation (0.9-1.5 µm)
was converted into the coherent visible radiation was obtained on the
basis of theoretical calculations. The measured threshold sensitivity of the
converter, 5×10-4 W cm-2, was found to be in the limits of theoretical estimation.
In recent years the bismuth oxide crystals, Bi203, find wide application in optical devices. In this connection, a detailed study of such crystals is of great importance. Particularly, in order to use the oxides with bismuth content in electron devices, qualitative parameters of the energy band structure should be needed /1, 2/. The main information about them can be obtained from optical investigations in the fundamental absorption region. Unfortunately, up to now, there a r e no reliable and complete investigations of the optical properties of Bi203. The present note reports results on the optical properties of Bi203 thin layers in the energy region hv = 1 . 0 to 40.0 eV with the use of synchrotron radiation (VEPP-BM, Institute of Nuclear Physics, Siberian Branch of the Academy of Sciences of the USSR).The bismuth oxide thin films were found to be of several crystalline modifications /3, 4/. The unit cells of 01 -, p-, and r-modifications a r e rather complicated for theoretical band structure calculations. However, the 6 -phase has a simpler structure (10 atoms per unit cell) and a higher symmetry (Td group), Therefore, 6 -phase bismuth oxide thin films are the subject of our investigations. The samples studied were obtained by hernial evaporation of metallic bismuth (99.99%) followed by oxidation in the air. The electron diffraction investigations showed that the films evaporated on sitall a t room temperature and annealed in a i r a t 200 O C for 1 0 h are polycrystalline and correspond to the d-phase of Bi203. The chemical composition of the films was determined by X-ray microanalysis using a DRON-2 diffractometer. The reflection measurements were carried out with the apparatus described in detail in /5/.
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