Browsing by Author "Petrova, D."

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Characterization of doped Bi4Ge3O12 single crystals by light-induced absorption, electrical and photoelectrical measurements
(2007-02-01)
Petrova, D.
;
Marinova, V.
;
Liu, R. C.
;
Lin, S. H.
;
Hsu, K. Y.
Measurement of light-induced absorption changes, dark- and photoconductivity have been performed on Bi4Ge3O12 crystals doped with Fe, Rh and Fe+Rh. All samples exhibited a strong photochromic effect at room temperature, which was fully reversible after thermal annealing. It was found that Rh-doped Bi4Ge3O12 crystals possess a lower dark conductivity (sigma(d) = 5.2 x 10(-14) (Omega.cm)(-1)) at room temperature in comparison with other investigated samples. New centers in the Bi4Ge3O12 inter-band structure, with thermal activation energies between 0.25 and 0.37 eV, have been created by doping with Fe and Rh. Fe-doped and Fe+Rh co-doped samples showed a non-linear photoconductivity dependence on light intensity, under illumination with a 514-nm laser.
Light-induced and holographic properties of ruthenium and manganese co-doped Bi(4)Ge(3)O(12) crystals
(2010-07-01)
Lin, S. H.
;
Marinova, V.
;
Lin, Y. C.
;
Petrova, D.
;
Chou, W. C.
The effect of Ru + Mn co-doping on the light-induced properties of Bi(4)Ge(3)O(12) (BGO) crystals is studied and compared with single Ru- and Mn-doped crystals. Optical absorption spectra of Ru + Mn co-doped crystal demonstrates a photosensitivity shift to the visible spectral range. In addition, a strong photochromic effect, being fully reversible by thermal annealing is observed. It is verified by photoluminescence emission that charge traps could be manipulated under ultraviolet (UV) excitation, as the photoluminescence intensity decreases revealing the existence of the state filling effect. Ru + Mn doping leads to a faster response time during holographic recording at 633 nm and a prolonged read-out process, especially after a preliminary exposure to UV light. The ability to modify the defect structure and corresponding absorption bands suggests the future potential for optical fixing using a two-step sensitization method.
Light-induced and holographic properties of ruthenium and manganese co-doped Bi4Ge3O12 crystals
(2010-07-01)
Lin, S. H.
;
Marinova, V.
;
Lin, Y. C.
;
Petrova, D.
;
Chou, W. C.
The effect of Ru + Mn co-doping on the light-induced properties of Bi4Ge3O12 (BGO) crystals is studied and compared with single Ru- and Mn-doped crystals. Optical absorption spectra of Ru + Mn co-doped crystal demonstrates a photosensitivity shift to the visible spectral range. In addition, a strong photochromic effect, being fully reversible by thermal annealing is observed. It is verified by photoluminescence emission that charge traps could be manipulated under ultraviolet (UV) excitation, as the photoluminescence intensity decreases revealing the existence of the state filling effect. Ru + Mn doping leads to a faster response time during holographic recording at 633 nm and a prolonged read-out process, especially after a preliminary exposure to UV light. The ability to modify the defect structure and corresponding absorption bands suggests the future potential for optical fixing using a two-step sensitization method.
The influence of Rh doping on the light-induced properties of Bi(4)Ge(3)O(12) single crystals
(2009-01-01)
Marinova, V.
;
Petrova, D.
;
Lin, S. H.
;
Hsieh, M. L.
;
Hsu, K. Y.
The influence of different doping concentrations of rhodium on the light-induced and holographic properties of BGO crystal is investigated. It is found that Rh addition generates sufficient density of traps for photoinduced charge carriers such that holographic gratings are successfully recorded in the blue-green spectral range. The measured steady state diffraction efficiency at 514 nm is 0.14%, which corresponds to a refractive index modulation of Delta n similar to 1.5 x 10(-6) for higher Rh concentration. A photochromic effect and nonlinear dependence of photoconductivity on light intensity are observed indicating deep level and shallow level contributions to the charge transport mechanism of Rh-doped BGO.
The influence of Rh doping on the light-induced properties of Bi4Ge3O12 single crystals
(2009-01-01)
Marinova, V.
;
Petrova, D.
;
Lin, S. H.
;
Hsieh, M. L.
;
Hsu, K. Y.
The influence of different doping concentrations of rhodium on the light-induced and holographic properties of BGO crystal is investigated. It is found that Rh addition generates sufficient density of traps for photoinduced charge carriers such that holographic gratings are successfully recorded in the blue-green spectral range. The measured steady state diffraction efficiency at 514 nm is 0.14%, which corresponds to a refractive index modulation of Delta n similar to 1.5 x 10(-6) for higher Rh concentration. A photochromic effect and nonlinear dependence of photoconductivity on light intensity are observed indicating deep level and shallow level contributions to the charge transport mechanism of Rh-doped BGO.