共查询到8条相似文献,搜索用时 15 毫秒
1.
利用GC Valley的准连续光(Quasi-cw)近似模型,研究了短脉冲激光(纳秒ns量级)在光伏光折变材料LiNbO3晶体中写入和擦除光折变光栅的过程,给出了空间电荷场随时间变化的表达式.理论研究表明,空间电荷场的形成和擦除与两个时间参量有关,在考虑或者不考虑光生伏打效应两种情况下,这两个参量随擦除光强的变化有基本相同的变化规律,光栅的写入和擦除有相同的结果.同样,擦除一个光栅所需的光能量在两种情况下也有相同的结果.因此,在短脉冲光入射光折变晶体材料情况下,考虑光生伏打效应与不考虑光伏效应,对短脉冲光在光折变LiNbO3晶体中写入和擦除光栅基本没有影响. 相似文献
2.
3.
S. M. Kostritskii 《Applied physics. B, Lasers and optics》2009,95(3):421-428
Original results on investigation of the photorefractive effect in straight channels and integrated-optical circuits such
as a directional coupler, Y-splitter and Mach–Zehnder interferometer, exploiting titanium-indiffused and proton-exchanged
LiNbO3 waveguides, are presented. It has been found that the photorefractive damage is non-negligible for IR radiation with wavelengths
near 1.5 μm in all circuits studied. The new methods for accurate evaluation of small extents of photorefractive effect are
proposed. 相似文献
4.
The present paper reports the DC conductivity measurements at high electric fields in vacuum evaporated amorphous thin films
of a-Se100−x
Sn
x
(x = 0, 2, 4, 6) glassy alloys. Current-voltage (I–V) characteristics have been measured at various fixed temperatures. In these samples, at low electric fields, ohmic behaviour
is observed. However, at high electric fields (E ∼ 104 V/cm), non-ohmic behaviour is observed. An analysis of the experimental data confirms the presence of space charge limited
conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC,
the density of defect states (DOS) near Fermi level is calculated. Increase in DOS with increase in Sn concentration has been
found which could be correlated with the electronegativity difference between the two elements used here in making the glassy
alloys. The peculiar role of the element Sn as an impurity in the pure Se glassy alloy is also discussed.
相似文献
5.
The EPR parameters, anisotropic g-factors g
x
, g
y
and g
z
for cu2+ ion and hyperfine structure constants A
x
, A
y
and A
z
for Cu2+ in LiNbO3 crystal are calculated by the method of diagonalizing the full Hamiltonian matrix. The crystal-field parameters contact with
the crystal structure by the aid of the superposition model. The optical transition parameters are calculated using Zhao crystal-field
model. The calculated results are in good agreement with the observed values. The results are discussed.
相似文献
6.
ZHANG Peng ZHAO Jianlin XU Honglai SUN Yidong YANG Dexing & WANG Meirong . Institute of Optical Information Science Technology School of Science Northwestern Polytechnical University Xi’an China . School of Science Xi’an Jiaotong University Xi’an China 《中国科学G辑(英文版)》2005,48(4):399-412
1 IntroductionSince the discovery of photorefractive effect by Ashkin et al. at the Bell laboratories in 1966[1], such effects of light-induced refractive index changes in electro-optic oxide crystals have attracted great attention because of their potential use in volume holo- graphic storage[2], optical information processing[3], optical spatial solitons[4], and light-induced optical waveguides[5―9]. The photo-induced index changes are the basis ofthe entire photorefractive phenomena in pho… 相似文献
7.
E.??liwińska S.?Mansurova U.?Hartwig K.?Buse K.?Meerholz 《Applied physics. B, Lasers and optics》2009,95(3):519-524
A new class of photo-refractive (PR) composite materials based on poly(N-vinylcarbazole) (PVK) (co-)sensitized with nano-crystalline lithium niobate (LiNbO3) is presented. The steady-state performance, as well as the kinetics of the photo-refractive grating formation, was investigated
by degenerate four-wave mixing (DFWM) and two-beam-coupling (TBC) experiments. We found an optimum content of LiNbO3 nano-particles of only 10−3 wt.%. Even at concentrations as low as 10−7 wt.% a notable effect of the nano-crystals was detected. This yields materials with improved PR performance compared to that
of the standard PR polymer material sensitized by TNF only. The role of LiNbO3 nano-particles is discussed in detail: The particles support generation and transport of the free-charge carriers. Furthermore,
they increase the electron trap density. 相似文献
8.
Nguen Tkhi Khoa T. N. Danilenko N. M. Novikovskii Ju. A. Kozinkin A. A. Novakovich R. V. Vedrinskii 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(8):1052-1053
The local Ti d densities of states in the valence band have been calculated in clusters of ATiO3 (A = Ca, Sr, Ba, Pb) crystals with perovskite structure by the full multiple scattering method. The d density of states in PbTiO3 crystal is found to significantly differ from that in other crystals. This fact indicates a significant effect of lead ions
on the chemical bond between Ti and O ions in this crystal. 相似文献