共查询到20条相似文献,搜索用时 10 毫秒
1.
We investigate non-volatile holographic data storage in photorefractive lithium niobate crystals. Infrared picosecond laser
pulses are used to write holograms after sensitizing the crystal with blue light from a cw-laser. The dependence of the dynamic
range and the photoconductivity on the pulse intensities and the recording wavelength is investigated in detail. The results
can be explained by a two-center model if the mean intensity of the laser pulses is considered. We demonstrate that several
fixed holograms can be multiplexed by employing the wavelength multiplexing technique. 相似文献
2.
A. T. Efremidis N. C. Deliolanis C. Manolikas E. D. Vanidhis 《Applied physics. B, Lasers and optics》2009,95(3):467-473
The photorefractive crystals of the sillenite family (Bi12SiO20 or BSO, Bi12GeO20 or BGO, and Bi12TiO20 or BTO) that belong to the cubic 23 point group are optically active, and exhibit the piezoelectric, elasto-optic, electro-optic
and electrogyration effect. In this paper we measure the dispersion of the electro-optic coefficient for all the crystals
of the sillenite family in the visible spectral range (500–800 nm). For this we measure by ellipsometry the polarization properties
of a beam transmitted in the transverse configuration under the action of an externally applied field. The experimental data
are fitted with an analytical expression of the beam polarization to find the electro-optic coefficient. The results show
a normal dispersion of the electro-optic coefficient in all three sillenite crystals, similarly to other electro-optic crystals. 相似文献
3.
Ye. P. Shershakov Yu. V. Miklyaev B. Ya. Zel'dovich 《Applied Physics A: Materials Science & Processing》1994,59(6):575-578
The saturation of the fundamental harmonic of the space-charge field is investigated experimentally in dependence of the contrast m and the amplitude of an external ac and dc field in a BTO crystal with a large electron-drift length. The behaviour of the first harmonic is explained qualitatively with the aid of perturbative analysis. 相似文献
4.
M. Abarkan M. Aillerie J. P. Salvestrini M. D. Fontana E. P. Kokanyan 《Applied physics. B, Lasers and optics》2008,92(4):603-608
We report the optical and dielectric properties in hafnium (Hf)-doped lithium niobate (LN) crystals. We investigated samples
of congruent composition with various doping concentration varying from 0 to 8 mol%. The clamped and unclamped values of the
electro-optic coefficient r
22 of Hf-doped LN and the corresponding dielectric permittivity as well, have been experimentally determined and compared with
the results obtained in undoped congruent LN crystals. We show that the electro-optic and dielectric properties are only slightly
affected by the introduction of hafnium ions, and therefore Hf-doped LN has the advantage of low photorefractive damage compared
with the undoped congruent LN. 相似文献
5.
High-resolution photorefractive gratings in nematic liquid crystals sandwiched with photoconductive polymer film 总被引:1,自引:1,他引:0
F. Yao Y. Pei Yu Zhang J. Zhang C. Hou X. Sun 《Applied physics. B, Lasers and optics》2008,92(4):573-576
Photorefractive gratings with high grating resolution were observed in the 20 μm thick low-molar-mass nematic liquid crystal
(NLC) cell with a separate photoconductive (PC) poly(N-vinylcarbazole) layer. An orientational grating with a grating spacing of 1.9 μm was produced. It is believed that a space–charge
field with small fringe spacing forms in the PC layer and its evanescent component penetrates into the NLC layer. The penetrated
evanescent field drives the NLC to reorient, and consequently the orientational grating forms. The model indicates that the
modulated field exists in several hundred nanometers near the surface, and thus the orientational grating is not full of the
NLC film, which is consistent with the observed phenomena of the multiple diffractions. Besides, asymmetric two-beam coupling
of 11.2% was achieved for the grating with a grating spacing of 1.9 μm, and a net gain coefficient of larger than 62 cm−1 was obtained. 相似文献
6.
O. Prakash H.-H. Lim B.-J. Kim K. Pandiyan M. Cha B. K. Rhee 《Applied physics. B, Lasers and optics》2008,92(4):535-541
Collinear broadband optical parametric generation (OPG) using periodically poled lithium niobate (PPLN) crystals were designed
and experimentally demonstrated with the quasi-phase matching (QPM) periods of 21.5, 24.0, and 27.0 μm. The broad gain bandwidth was accomplished by choosing a specific set of the period and the pump wavelength that allows
the group velocities of the signal and the idler to match close to the degeneracy point. OPG gain bandwidth and also the spectral
region could be controlled by proper design of QPM period and pump wavelength. The total OPG gain bandwidth of 600, 900, and
1200 nm was observed for the PPLN devices with QPM periods of 21.5, 24.0, and 27.0 μm, respectively. We have also observed multiple color visible generation whenever the OPG spectrum was significantly broad.
From the visible peaks of the three PPLN samples, it is found that broad gain bandwidth is crucial in the temperature-insensitive
collinear simultaneous RGB generation from a single crystal. 相似文献
7.
We report on the formation of spatial optical solitons in photorefractive media using picosecond laser pulses. Solitons are
generated with laser pulses in the visible and infrared wavelength region using photorefractive strontium barium niobate.
The dynamics of the soliton formation and the region of existence is studied in detail. 相似文献
8.
Exceptionally high values of photorefractive gain coefficient of up to 100 cm-1 have been observed in Fe-doped and Fe/Tb-doped crystals of photorefractive lithium niobate. It is believed that these are
the highest observed coefficients of any crystalline photorefractive medium. Accurate measurements of gain coefficient have
been possible for the first time by using a specially cut triangular crystal which allows the use of short interaction lengths
and the complete elimination of surface reflections by having the beams incident at Brewster’s angle. Experimental results
are consistent with a simple model of photorefractive beam coupling up until the onset of noise which is observed to deplete
the pump for interaction lengths longer than 1 mm.
Received: 28 September 1998 / Revised version: 8 January 1999 / Published online: 31 March 1999 相似文献
9.
A. Ruso M. Aillerie N. Fressengeas M. Ferriol 《Applied physics. B, Lasers and optics》2009,95(3):573-578
This paper reports the engraving of an optical waveguide inside a LiNbO3 crystal fiber via the photorefractive effect and an optical vortex. Afterwards this waveguide was successfully tested and
its properties evidenced. 相似文献
10.
H. J. Ravindra K. Chandrashekaran W. T. A. Harrison S. M. Dharmaprakash 《Applied physics. B, Lasers and optics》2009,94(3):503-511
Single crystals of a chalcone co-crystal (C18H19NO4/C17H16NO3Br; 0.972/0.028) have been grown by slow evaporation from solution. The powder second harmonic generation (SHG) efficiency
of this chalcone co-crystal is 7 times that of urea. The dependence of second harmonic (SH) intensity on particle size revealed
the existence of phase matching direction in this crystal. The large SHG efficiency observed is mainly due to the unidirectional
alignment of molecular dipoles, in which the dipole moment of each molecule adds to establish a net polarization. The weak
N–H⋅⋅⋅O hydrogen-bond interactions help to stabilize the noncentrosymmetric crystal packing and also contribute partly to the SHG.
The better thermal stability, transparency and high laser damage resistance (>1.5 GW cm−2 at 532 nm, 8 ns) of this chalcone co-crystal indicate that it is a promising material for frequency doubling of diode lasers
down to 470 nm. This molecule also shows a third-order NLO response and good optical limiting property of 8 ns laser pulses
at 532 nm. The mechanism for optical limiting in this chalcone was attributed to two-photon induced excited state absorption
that leads to reverse saturable absorption. The structure–property relationship in this chalcone and related compounds is
discussed based on the experimental results and semiempherical hyperpolarizability calculations. 相似文献
11.
P. Zhang S. Liu C. Lou Y. Gao J. Zhao J. Xu Z. Chen 《Applied physics. B, Lasers and optics》2009,95(3):559-563
We theoretically and experimentally demonstrate that a nonconventionally biased photorefractive crystal can support hybrid
nonlinearity, i.e., coexistence of self-focusing and self-defocusing nonlinearities under an identical bias condition. It
is revealed that the nonlinearity experienced by a one-dimensional (stripe) beam can be switched between self-focusing and
self-defocusing solely by changing the beam orientation. For a two-dimensional beam, the hybrid nonlinearity leads to unusual
nonlinear beam dynamics with enhanced anisotropy and nonlocality. 相似文献
12.
R. Montenegro A. Shumelyuk R. Kumamoto J. F. Carvalho R. C. Santana J. Frejlich 《Applied physics. B, Lasers and optics》2009,95(3):475-482
Holographic recording in a vanadium-doped B12TiO20 (BTO) photorefractive crystal puts into evidence a large hole–electron competition showing a fast and a slow hologram components.
From the fast component evolution, some material parameters for the electron-donor photoactive centers are computed. The wavelength-resolved
photoconductivity is shown to be strongly modified by V-doping compared to undoped and doped BTO with other elements. The
increase of photoconductivity by green light preexposure is almost negligible here if compared with undoped BTO. Activation
energy for dark conductivity measured for BTO:V is similar to that for undoped BTO, as measured close to room temperature,
but sensibly lower than the value reported in the literature for a much higher temperature range. Optical absorption and EPR
spectra do confirm already published results and suggestions about the possible role of vanadium in the sillenite structure. 相似文献
13.
S. Vatnik M. C. Pujol J. J. Carvajal X. Mateos M. Aguiló F. Díaz V. Petrov 《Applied physics. B, Lasers and optics》2009,95(4):653-656
The three thermo-optic coefficients of the biaxial laser host KLu(WO4)2 are measured at 633 nm by a deflection method. Their values at 300 K amount to ∂
n
g
/∂
T=−7.4×10−6 K−1; ∂
n
m
/∂
T=−1.6×10−6 K−1 and ∂
n
p
/∂
T=−10.8×10−6 K−1. Nearly athermal propagation directions are found for polarizations along the N
m
and N
p
dielectric axes. 相似文献
14.
T. P. J. Han E. Cantelar G. Lifante F. Cusso F. Jaque 《Applied physics. B, Lasers and optics》2009,94(2):209-214
This paper reports on the spectroscopy properties, absorption and luminescence, of Cr3+ ions in singly doped, ZnO-codoped, and Zn in-diffused LiNbO3:Cr crystals. In addition to the broad absorption, inter-ionic transitions ascribed to Cr3+ ions located in Li+ and Nb5+ sites; [Cr]Li and [Cr]Nb centres two absorption bands at higher energy are reported and ascribed to the charge transfer transitions of the Cr3+ ions of the two defect centres.
The charge transfer transitions are used as optical probe to study the role of the Zn ions in the Zn in-diffused LiNbO3:Cr samples. It has been observed that the Zn-in-diffused processes created [Cr]Nb centres in the diffusion zone. The location of the diffused Zn2+ ions is considered to be in Li+ site, displacing the Cr3+ ions from the Li+ sites, [Cr]Li, to the Nb5+ positions, [Cr]Nb. 相似文献
15.
Y. Tan F. Chen P. P. Beli?ev M. Stepi? A. Maluckov C. E. Rüter D. Kip 《Applied physics. B, Lasers and optics》2009,95(3):531-535
Photovoltaic photorefractive binary waveguide arrays are fabricated by proton implantation and selective light illumination
on top of an iron-doped near stoichiometric lithium niobate crystal. Linear discrete diffraction and nonlinear formation of
gap solitons were investigated by single-channel excitation using Gaussian light beams coupled into either wide or narrow
waveguide channels. The results show that, at low power, linear light propagation leads to discrete diffraction, whilst for
higher input power the focusing mechanism dominates, finally leading to the formation of gap solitons in the binary waveguide
arrays. Our simulation of light propagation based on a nonlinear beam propagation method confirms the experimental findings. 相似文献
16.
D. Nau A. Christ H. Giessen A. Wagner A. Euteneuer M. Salvador E. Mecher K. Meerholz 《Applied physics. B, Lasers and optics》2009,95(1):31-35
Photorefractive polymers allow to reversibly record holograms over a broad spectral range. This capability offers the possibility
to store the information contained in ultrafast optical pulses (i.e., time domain) in the frequency domain. We demonstrate
a storage bandwidth of >80 nm around 800 nm (i.e., >36 THz), giving a temporal resolution for Gaussian pulses of 13 fs at
room temperature. Time reversal of a pulse train of 130 fs pulses confirms these capabilities. 相似文献
17.
I. V. Kedyk P. Mathey G. Gadret A. A. Grabar K. V. Fedyo I. M. Stoika I. P. Prits Y. M. Vysochanskii 《Applied physics. B, Lasers and optics》2008,92(4):549-554
In this work we report results on electro-physical, optical and photorefractive investigations for Sb-doped Sn2P2S6 crystals. The crystals are obtained by two methods: the vapour-transport technique and the Bridgman technique using stoichiometric
Sn2P2S6 composition with different amounts of antimony in the initial compound. The good optical quality of the crystals obtained
with the Bridgman technique is underlined. The dependences of the photorefractive two-beam coupling coefficient and the grating
build-up time are investigated at the wavelength of 633 nm. It is found that the sample doped with 1.5% of Sb is characterized
by an optimal combination of the main photorefractive parameters exhibiting a fairly high two-beam coupling coefficient (up
to 20 cm−1) and a short response time (1.3 ms) that is the shortest among all the previously studied Sn2P2S6 crystals in the red spectral region. 相似文献
18.
J. Lamela D. Jaque A. Rodenas F. Jaque G. A. Torchia J. R. Vazquez C. Mendez L. Roso 《Applied Physics A: Materials Science & Processing》2008,93(1):177-181
Near-field-optical-microscopy has been used to study the micro-modifications caused by femtosecond laser pulses focused at
the surface and in the volume of lithium niobate crystals. We have found experimental evidence of the existence, close to
femtosecond ablation craters, of periodic modifications in the surface reflectivity. In addition, the potential application
of near-field-optical microscopy for the spatial location of permanent modifications caused by femtosecond pulses focused
inside lithium niobate crystals has been also demonstrated. 相似文献
19.
A. Harhira L. Guilbert P. Bourson H. Rinnert 《Applied physics. B, Lasers and optics》2008,92(4):555-561
Photoluminescence related to the bound polaron NbLi4+ is investigated as a function of temperature and incident light intensity in iron-doped lithium niobate crystals with various
iron concentrations. Experiments are done under constant-wave (CW) and pulsed illumination. Its found that the decay time
is always monoexponential. The radiative lifetime, the activation energy of the nonradiative lifetime and the quenching temperature
are only weakly sensitive to iron concentration. On the other hand, the magnitude of the photoluminescence signal seems strongly
correlated to the Fe2+ concentration, and the superlinear regime evidenced at low CW illumination definitely confirms that polaron excitation in
lithium niobate is a two-step process. 相似文献
20.
Two-photon induced photorefraction in undoped lithium tantalate crystals with different compositions
I. S. Steinberg I. E. Kalabin P. E. Tverdokhleb 《Applied physics. B, Lasers and optics》2009,95(3):407-411
Two-photon interband photorefraction in undoped lithium tantalate crystals with composition ranging from 47.95 to 49.6 mol%
of lithium oxide was demonstrated at the wavelength of 532 nm. The photorefractive properties were examined with holographic
method. Two-photon holograms were recorded with high holographic sensitivity, large refractive index change, and fast hologram
writing time. Permanent changes of the refractive index have been obtained. These holograms can be read nondestructively at
the wavelength of 660 nm using heterodyne method. Holographic characteristics strongly depend on composition. 相似文献