共查询到20条相似文献,搜索用时 15 毫秒
1.
The dependence of the maximal diffraction efficiency of a volume reflection hologram recorded in a cubic optically active
photorefractive piezocrystal on the crystal thickness is investigated. The theoretical analysis is fulfilled on the basis
of the coupled wave equations in a static grating approximation taking into account the linear electro-optic, inverse piezoelectric,
and photoelastic effects. The optimal cuts of the crystals with various thickness for which the maximal diffraction efficiency
of the reflection hologram can be attained are determined. It is shown that the optical activity of the crystal is responsible
for a variety of the optimal cuts corresponding to different crystal thicknesses. Effect of the crystal on the dependence
of the maximal diffraction efficiency of the reflection hologram on a crystal cut is discussed. 相似文献
2.
J. V. Alvarez-Bravo N. Bolognini L. Arizmendi 《Applied physics. B, Lasers and optics》1996,62(2):159-164
Changes in the angular Bragg selectivity of volume holograms stored in photorefractive LiNbO3 are analysed for different experimental conditions in the transmission geometry. The effects of the refractive-index-change amplitude, the grating period, the modulation depth, and the wave-front modulation of the signal beam are considered. A very good agreement of the results with the off-Bragg diffraction theory is observed. 相似文献
3.
Volume phase-hologram formation by the photorefractive effect in KNbO3 is accompanied by a stationary energy transfer between writing beams. The change in energy transfer by applying an electric
field on the reduced crystals is shown to be due to an efficient increase in migration length which can reach values comparable
or larger than the fringe spacing. It is demonstrated that photovoltaic contribution to the diffraction efficiency and energy
transfer is rather small in reduced KNbO3 and that diffusion of photogenerated free holes is the dominant charge transport for the photorefractive effect in unbiased
crystals. The experimental results for diffraction efficiency and energy transfer as a function of grating spacing, electric
field, light intensity and temperature is well described by a recent theory of Kukhtarev and Vinetskii. 相似文献
4.
A comprehensive technique has been used to detect diffraction from the second and the third nonlinear spatial harmonic components, along with the fundamental harmonic of volume photorefractive gratings recorded in a channel waveguide in a LiNbO3 substrate. For the first time to our knowledge, efficient diffraction from the higher spatial harmonic components of a photorefractive grating has been detected in reflection geometry. The dependence of a Bragg wavelength shift on the order of nonlinearity is also reported. 相似文献
5.
6.
The multi-layers coupled-wave theory is extended to systematically investigate the pulse shaping and diffraction properties
of a system of multi-layers reflection volume holographic gratings (MRVHG) under ultrashort laser pulse (ULP) readout. The
combined effects that the grating parameters such as the number and thickness of layers and gaps between them and the pulse
duration of the input ULP have on the pulse shaping properties are considered. The pulse profiles of the diffracted and transmitted
beams, the diffraction bandwidth, and the total diffraction efficiency are presented. The calculated results we have derived
permit an optimal choice of grating parameters for the pulse shaping and process applications. 相似文献
7.
Salvatore Di Girolamo Roman V. Romashko Alexei A. Kamshilin 《Optics Communications》2010,283(1):128-317
We present a novel configuration of an interferometer which is implemented by using vectorial wave mixing in the orthogonal geometry of wave interaction in a cubic photorefractive crystal, for the detection of small phase transients. The orthogonal geometry of wave interaction allows the linear regime of the phase-to-intensity transformation even when phase transients are encrypted in a depolarized wave without using any polarizing element. The use of a depolarized beam without a polarizing element strongly diminishes the noise level, thus increasing the sensitivity to phase transients. 相似文献
8.
N.C. Deliolanis A.G. Apostolidis E.D. Vanidhis D.G. Papazoglou 《Applied physics. B, Lasers and optics》2002,75(1):67-73
We study the influence of the application of an external electric field on the grating formed in (1-10) and (111)-cut photorefractive
sillenite crystals. Optimum conditions for application of the bias field are examined, taking into account the shift of the
grating orientation for maximum diffraction efficiency along the crystal depth. The contribution of the piezoelectric effect
is considered both in the electro-optic tensor and space charge field calculations. An analysis on the diffractive properties
under these optimum conditions shows an increase of 30% in maximum diffraction efficiency in Bi12GeO20, and experimental verification for this is provided.
Received: 5 November 2001 / Revised version: 18 April 2002 / Published online: 8 August 2002 相似文献
9.
The main conditions and parameters for obtaining surface relief total internal reflection diffraction gratings in conical mounting are presented. Calculated and experimental investigations reveal that there are ranges of grating periods, incidence angles, diffraction angles and gratings depths for which such gratings could be obtained, both for TE and TM polarizations. With optimized grating parameters the diffraction efficiency of the total internal reflection diffraction gratings can be greater than 90%. 相似文献
10.
A. Thompson N. Nazhestkina A. Siahmakoun G. Duree N. Roesler 《Applied physics. B, Lasers and optics》2003,76(5):547-554
We present experimental investigations of electrical fixing techniques in Ce:SBN:60. The effect of crystal fatigue on the
diffraction efficiency of electrically fixed photorefractive gratings is studied. We observed that applying an ac field to
the crystal eliminated crystal fatigue and improved diffraction efficiency. A controllable diffraction efficiency of a photorefractive
grating is presented. A reproducible diffraction efficiency of up to 75% is obtained using a write-reveal grating technique
with high-voltage pulses of opposite polarity. We also show that the diffraction efficiency can be controlled by varying the
intensity of the writing beams incident to the crystal during the recording process. A method of determining the hysteresis
loop using the domain-fixing technique is proposed. The dependence of the diffraction efficiency on the direction of the applied
electric field while writing the hologram is studied. Our experiments show that, during writing, when the electric field is
applied opposite to the c axis the grating can be successfully revealed with both positive and negative dc voltages. However,
when the grating is written with a field parallel to the c axis, the grating can be revealed only with a field applied in
the opposite direction.
Received: 28 October 2002 / Revised version: 28 February 2003 / Published online: 14 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-812/872-6167, E-mail: azad.siahmakoun@rose-hulman.edu 相似文献
11.
We report the measurement of the diffusion length, the Debye screening length and the quantum efficiency of photoelectron
generation in strongly light absorbing photorefractive Bi12TiO20 crystals, using fringe-locked running hologram experiments. The effective applied electric field inside the sample is also
computed and self-diffraction is considered. The novelty here, as compared to formerly reported experiments, is that the diffraction
efficiency is now measured simultaneously with the hologram speed v. From these data the above referred to photorefractive
and experimental parameters are obtained without the need for additional experiments. The method is used to analyze two photorefractive
Bi12TiO20 crystal samples, in different experimental conditions, using the 514.5 nm wavelength. The computed parameters are in good
agreement with the available information about these samples.
Received: 23 November 2000 / Published online: 21 March 2001 相似文献
12.
The photochromic bacteriorhodopsin (BR) film can be used as a rewritable holographic recording medium. Due to the saturation absorption and the scattering and reflecting lights from the BR film, the grating contrast-ratio of the hologram is diminished during the hologram recording. When the intensity of the recording light is low, the influence of the saturation absorption and the scatter and reflection of BR film on the grating contrast-ratio is weak. But for the case of intense recording light, this influence is more serious. It is found that the influence of the auxiliary violet light on the holographic kinetics of diffraction efficiency is distinct under different recording intensities. At the low recording light intensity, the steady diffraction efficiency is increased and the peak diffraction efficiency is suppressed by the auxiliary violet light. But for intense recording light, the steady diffraction efficiency and the peak diffraction efficiency are both increased by the auxiliary violet light. Based on the two-state model of BR photochromism, we give a good theoretical explanation to the above phenomena. 相似文献
13.
The photorefractive planar lens for converting a vertical incident plane wave to a lateral-spread spherical wave and vice versa, is suggested. Using the two-beam coupled-wave theory, the coupled wave equations are derived and their half-analytical solutions are also given in terms of an infinite series. The diffraction properties (beam profiles, diffraction efficiency) of the local volume grating in the lens are presented. And the focusing property of the lens is discussed and compared with that of an ideal convergent spherical wave. It is demonstrated that the suggested photorefractive planar lens shows a good focusing effect. 相似文献
14.
Y. H. Ja 《Applied physics. B, Lasers and optics》1984,35(3):141-144
A detailed analysis is given of the properties of the algebraic equations obtained when solving directly the nonlinear coupled-wave equations for degenerate two-wave mixing in a reflection geometry. An efficient method is developed for computing the appropriate root only amongst the multiple roots of these algebraic equations. 相似文献
15.
The anisotropic Bragg diffraction of the volume holographic gratings in photorefractive crystals are investigated based on the model of anisotropic coupled-wave theory. The effect of the initial intensity ratio and the recording angles of the two recording waves on the anisotropic Bragg diffraction properties is discussed. It is shown that both the ratio of the initial intensity and the incident angles of the recording waves are selective action for the anisotropic Bragg diffraction efficiency of the volume holographic gratings, while these two recording conditions are not selective action for the isotropic Bragg diffraction. Furthermore, the Bragg phase matching condition of anisotropic diffraction is analyzed when the recording angles change. 相似文献
16.
M. Carrascosa F. Agulló-Rueda F. Agulló-López 《Applied Physics A: Materials Science & Processing》1992,55(1):25-29
A theoretical model based on the Dember mechanism is proposed to describe the steady state photorefractive gratings generated in semiconductor multiple quantum wells (MQW). It has been applied to an GaAs/AlGaAs MQW in parallel configuration (external electric field applied parallel to the MQW layers) for which recent experimental data are available. The model predicts a dependence of the first-order diffraction efficiency on the applied field in qualitative accordance with experiments, including the occurrence of saturation at high field values. Absolute values of the efficiencies are in good agreement with the experimental ones. Finally, high second-order diffraction efficiencies, associated with the development of a perpendicular space charge field, are also predicted by the model. 相似文献
17.
K. C. Johnson 《Applied Physics A: Materials Science & Processing》1981,25(3):357-360
The phenomenon of image reconstruction from an absorptionless volume hologram is analyzed using coupled-wave diffraction theory.
Reconstruction efficiency formulas are derived, which apply when the hologram intermodulation component is negligible and
when no extraneous diffracted orders of significant amplitude are generated. Both transmission and reflection holograms are
considered, and the analysis is developed for diffraction geometries in which polarization effects are appreciable. 相似文献
18.
利用一维耦合波理论研究了入射方向相互垂直的一束平面波与一束柱面波干涉形成光折变局域体全息光栅的波前转换情况。给出了透射波和衍射波振幅的解析表达式。讨论了该局域体全息光栅的几何尺寸以及全息透镜的焦距对光栅衍射效率的影响。结果表明,随着光栅横向尺寸的增加,光栅的衍射效率也逐渐增加。然而,光栅的衍射效率却随着光栅纵向尺寸的增加而减小。全息透镜的焦距越长,光栅的衍射效率也越大。此外,分析了光栅的布拉格选择特性,该光栅具有非常好的角度选择特性。在平面波与柱面波干涉形成全息透镜的设计中,为了获得最优的衍射效率,应当根据要求合理地选择记录所用柱面波和设计光栅的几何尺寸。 相似文献
19.
A. Marrakchi J. P. Huignard P. Günter 《Applied Physics A: Materials Science & Processing》1981,24(2):131-138
The diffraction efficiency and energy transfer are investigated in photorefractive Bi12SiO20 crystals (BSO). Dependence on fringe spacing, electric fields, light intensity and rise-time constants are reported. The
optimum crystallographic orientation for each effect is determined for vertical polarization of the recording beams. It is
shown that beam coupling is a very sensitive phenomenon in BSO crystals where charge transport lengths are equivalent to usual
fringe spacings. Experimental results are interpreted on the basis of the nonlinear theory of self-diffraction developed by
Kukhtarev et al. [10]. 相似文献
20.
A series of bromine-vapour bleached, planar, volume holograms were formed in silver halide emulsion. The holograms were characterised by measuring the variation in intensity of the transmitted replaying beam with angles at several wavelengths. The results were investigated using coupled-wave theory, allowing for the existence of grating harmonics and higher diffraction orders. The effects of first, second and third grating harmonics were found in the experimental results. Modulation profiles synthesised using the results suggested the presence of a small fourth harmonic in the higher exposure holograms. 相似文献