共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
We present the numerical results of the photorefractive two-wave mixing in the presence of an incoherent beam by considering
the influence of the ratios of the intensities and the light-excitation cross sections of the incoherent beam to the coherent
beams on the space-charge field and the effective coupling coefficient. The results show that the incoherent beam can control
the intensity of the coherent beams effectively. The experimental results agree with the theory well. One application is demonstrated
to obtain the positive and negative coherent replicas of an incoherent image. The coherent images have a resolution of 80.6 line
pairs/mm.
Received: 2 March 1999 / Revised version: 26 July 1999 / Published online: 20 October 1999 相似文献
3.
V.V. Shepelevich Y. Hu A. Firsov E. Shamonina K.H. Ringhofer 《Applied physics. B, Lasers and optics》1999,68(5):923-929
Simple analytical expressions for the dependence of the maximum gain on the polarization angle of the interacting light waves
and the crystal thickness are obtained for two-wave mixing in a cubic optically active piezoelectric crystal. By applying
the theory to Bi12SiO20 and Bi12TiO20 crystals, the optimum gain is found also with respect to the grating orientation. The r?le of the (inverse) piezoelectric
effect is investigated.
Received: 23 November 1998 / Revised version: 8 January 1999 / Published online: 7 April 1999 相似文献
4.
Photorefractive properties and self-pumped phase conjugation in a series of BaTiO3 crystals 总被引:2,自引:0,他引:2
X. Xu Z. Wang X. Yang J. Liu X. Mu Z. Shao H. Xu H. Luo 《Applied physics. B, Lasers and optics》2001,73(3):223-226
This paper presents the experimental results of two-wave mixing and self-pumped phase conjugation (SPPC) in barium titanate
(BaTiO3) crystals doped with Rh or Ce. It has been shown that the main parameters of SPPC depend very strongly on the concentrations
of dopants, the incident angles and the crystal cut used. High gain in two-wave mixing corresponds to low phase-conjugate
reflectivity in all samples. It is impossible to maintain the highest reflectivity and gain simultaneously, because the gain
will definitely be limited when we try to get the highest reflectivity, and vice versa. Some qualitative explanation of the
experimental results is also given.
Received: 5 January 2001 / Final version: 25 May 2001 / Published online: 19 September 2001 相似文献
5.
Abe S Fujishima T Tsubone T Fujimura R Ono H Matoba O Oda K Shimura T Kuroda K 《Optics letters》2003,28(6):420-422
The photorefractive effect in a nominally undoped 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 single crystal is measured. We report what is, to our knowledge, the first observation of the photorefractive effect in Pb-based relaxor ferroelectric crystals. The crystal is grown by the flux solution method. Then it is cut into a 2 mm x 4 mm x 8 mm piece and electrically poled along the [111] direction. The coupling constant of the two-wave mixing is 17 cm(-1), and the normalized time constant under 1-W/cm(2) illumination is 12 s at a wave-length of 476 nm. The effective trap density is calculated as 5 x 10(16) cm(-3) from the Debye screening length under the assumption of Kukhtarev's band-transport model. The dominant carrier is identified to be holes from the direction of two-wave mixing energy transfer. 相似文献
6.
7.
Y. H. Ja 《Optical and Quantum Electronics》1983,15(6):529-538
Using the shooting method, one of the numerical methods to solve two-point boundary-value problems, numerical solutions of the nonlinear coupled-wave equations in degenerate two-wave and four-wave mixing can be obtained. In this first part of the paper the general shooting method is described, and then applied to two-wave mixing in a reflection geometry. Computed results are presented in graphical form. Comparison between the shooting method and the direct numerical method [1] is made also. In the second part of the paper, numerical solutions for four-wave mixing in a reflection geometry will be given. 相似文献
8.
Y. Ding H. J. Eichler B. Smandek 《Applied Physics A: Materials Science & Processing》1992,55(1):21-24
We report a method to increase the photorefractive two-wave mixing gain coefficient in semiconductors by using additional incident laser radiation. Two auxiliary beams are used to optimize the spatial distribution of an applied electrical field via modulation of the photoconductivity of the sample. By applying a voltage of 3.5 kV on a 4.3 mm thick InP:Fe crystal we obtain a two-wave mixing gain of 9 cm–1. This is about 50% larger than that obtained without auxiliary beams. 相似文献
9.
S. A. Podoshvedov 《JETP Letters》2002,75(10):503-506
Evolution of the vacuum fluctuations in the two-wave mixing of the optical fields propagating in a birefringent fiber is studied. The two-wave mixing in the birefringent fiber was suggested as a possible scheme for the entangled-state generation. Our treatment in studying the entangled-state generation uses depleted pump approximation and enables one to trace the influence of the input conditions of classical optical fields on the evolution of vacuum squeezing. We report the periodical modulation of the vacuum squeezing when the input relative phase of coherent waves varies. The measure of nonclassical correlations imposed on the generated light is calculated. 相似文献
10.
S. Balasubramanian I. Lahiri Y. Ding M.R. Melloch D.D. Nolte 《Applied physics. B, Lasers and optics》1999,68(5):863-869
The photorefractive response to an applied electric field is measured in a photorefractive quantum well, providing evidence
in favor of the nonlinear transport in the device due to the hot electrons. The reduced mobility of the hot electrons limits
the drift length, and thereby limits fringe overshoot. Thus the nonlinear transport prevents the slowing down of the grating
writing rate for increasing fields which is common in bulk photorefractives. The photorefractive phase shift in transverse-field
photorefractive quantum wells is measured as a function of the frequency offset between two laser writing beams that generate
moving gratings. The two-wave mixing passes through a maximum at an optimum frequency which depends on the magnitude and the
sign of the applied dc electric field. The phase shift associated with the moving grating adds or subtracts from the static
phase shift induced by hot-electron transport in the semiconductor quantum wells, depending on the sign of the field and the
sign of the dominant photocarriers. We observe a linear relationship between the roll-off frequency and the power of the writing
beams.
Received: 26 November 1998 / Revised version: 22 January 1999 / Published online: 12 April 1999 相似文献
11.
Y.H. Ja 《Optics Communications》1985,53(3):153-158
The effect of multiple internal reflections on the stationary energy transfer in degenerate two-wave mixing, in a reflection geometry, with photorefractive crystals is studied. Numerical results obtained by using the shooting method are presented graphically. Generally it is found that the presence of multiple internal reflections reduces the amount of energy transferred between the two interacting beams. However, under some special conditions the energy transfer can be enhanced. 相似文献
12.
We present a technique to convert a multimode-transverse beam obtained from a multimode large core fiber amplifier into a
single-mode beam by means of two-wave mixing in an infrared-sensitive Rh:BaTiO3 crystal.
Received: 26 March 2001 / Revised version: 27 March 2001 / Published online: 27 April 2001 相似文献
13.
对LiNbO3: Fe晶体中二波耦合过程进行了动态观测.进一步探讨了LiNbO 3:Fe晶 体中弱光放大的物理机理.发现LiNbO3 : Fe晶体中二波耦合过程的弱光放大 对c轴指 向有明显的依赖关系,虽然光生伏打效应对光生载流子的迁移有主要贡献,但扩散机理的贡 献仍不可忽略.弱光最终得到放大是瞬态能量转移与扩散机理引起的能量转移的共同贡献.弱 光放大达到准稳态之后的下降过程为瞬态能量转移的时间指数衰减过程与光散射引起的能量 耗散的共同贡献.
关键词:
光折变效应
光放大
掺杂铌酸锂 相似文献
14.
A method of tomographic imaging is proposed in which two-wave mixing in a photorefractive crystal is used with wavelength scanning of a laser diode and phase modulation of the pump beam. This method provides full optical processing and is effective for weak light from objects because of the use of two-wave mixing. The depth resolution of the method was ~1 cm when the wavelength-scanning width was ~0.02 nm . 相似文献
15.
理论分析和实验观测了非相干背景光辐照下掺杂LiNbO3晶体中的二波耦合,发现非相干背景光能够在很大范围内灵活有效地控制信号光增益,抑制扇形效应,提高信噪比,缩短光栅的建立时间.入射光光强比一定时,适当地增大背景光光强可以使光栅响应时间减小一个数量级.尤其对于抽运光光强远大于信号光光强的情况下,上述作用更为明显.
关键词:
光折变
二波耦合
非相干背景光 相似文献
16.
Ce:Fe:LiNbO3晶体的全息存储和相位共轭特性的研究 总被引:6,自引:1,他引:5
本文用提拉法从熔体中生长了Ce:Fe:LiNbO_3晶体,并采用二波混合和简并四波混合方法研究和测试了晶体的全息衍射效率和相位共轭反射率.以Ce:Fe:LiNbO_3晶体作为存储元件和相位共轭镜,实现了光学实时全息关联存储. 相似文献
17.
S. A. Podoshvedov 《JETP Letters》1998,67(11):927-933
It is shown that generation of quadrature-squeezed states of a vector electromagnetic field in which quantum fluctuations in one of the quadrature components are smaller than in the coherent state can occur in cubically nonlinear media (birefringent fibers) with efficient energy transfer between the polarization modes of the field. It is shown that for certain distributions of the initial total power between modes, light with suppressed quantum fluctuations in both polarization modes of the vector field is formed at the fiber exit. The optimal conditions for obtaining quadrature-squeezed light are determined. New analytical expressions are obtained for the degree of squeezing in the two polarization modes in the case when there is no energy transfer between the polarization components of the field propagating in the fiber (eigenmodes of two-wave mixing). 相似文献
18.
Y. H. Ja 《Applied physics. B, Lasers and optics》1984,33(1):51-56
A theoretical study is presented of a special case of stationary energy transfer in degenerate two-wave mixing in a reflection geometry. The two interacting beams consist of a beam and its first-order internal reflection component created at the boundary of a nonlinear medium. Numerical results obtained from the computer calculations are presented as graphs. It is found that, under suitable conditions, this phenomenon can be used to eliminate the multiple internal reflections. 相似文献
19.
G. Mandula M. A. Ellabban R. A. Rupp M. Fally E. Hartmann L. Kovács 《辐射效应与固体损伤》2013,168(1-6):173-179
The activation energy of thermal fixing of photorefractive gratings is determined in congruent and nearly stoichiometric lithium niobate crystals, both doped with iron or manganese. The novel technique called holographic scattering method is compared with the standard two-wave mixing method. A measurement of the angular distribution of the self scattered intensity and its possible analytical function is presented. The mathematical problems of the holographic scattering method are discussed applying the angular distribution functions. 相似文献
20.
Hao Tian Zhongxiang Zhou Dewei Gong Haifeng Wang Yongyuan Jiang Chunfeng Hou 《Optics Communications》2008,281(6):1720-1724
We report the successful growth of paraelectric potassium lithium tantalate niobate (KLTN) single crystal doped with iron. Detailed investigations have been made on the photorefractive properties of the as-grown crystal. The key parameters such as space-charge field, grating response time, photorefractive sensitivity and sign of the dominant charge carrier were obtained by two-wave mixing technique. 1.7 mm thick sample exhibits a high diffraction efficiency of 78% at the external field of 3.3 kV/cm and a sensitivity of 1.49 × 10−10E0 cm2/J. The two-wave mixing gain coefficient increases linearly with external field, and reaches a large value of 19.4 cm−1 at 4 kV/cm. Based on experimental results, iron is an effective dopant to KLTN which shows high diffraction efficiency and two-wave mixing gain coefficient. 相似文献