Kebin Xu

Optical perfect shuffle using Wollaston prisms.

The 2-D optical perfect shuffle is demonstrated in an imaging system which uses Wollaston prisms for replicating the input image. Full parallelism and high light efficiency are achieved using this perfect shuffle system.

Self-pumped phase conjugation of 18°-cut Ce-doped KNSBNcrystal at 632.8 nm

We report the self-pumped phase conjugation of an 18°-cut Ce-doped (KyNa1−y)2m(SrxBa1−x)1−m Nb2O6 crystal at a 632.8-nm He–Ne laser wavelength. A maximum phase-conjugation reflectivity of 84.3% has been measured. In addition, its incident angular response and time response are measured.

Enhancement of the exponential gain coefficient as a result of the light-fanning effect in thin doped LiNbO 3 crystals

The enhancement of the exponential gain coefficient of two-beam coupling in several thin samples of doped LiNbO3 crystals is reported. The mechanism is analyzed by light crawling that originates from the light-fanning effect. Some experimental results to support the explanation are presented.

Performance of real time associative memory using a photorefractive crystal and liquid crystal electrooptic switches.

We present a real time holographic associative memory implemented with photorefractive KNSBN:Co crystal as the memory element and a liquid crystal electrooptic switch array as the reflective thresholding device. Our experiment stores and recalls two images and shows that the system has real time multiple-image storage and recall functions. An associative memory with a dynamic threshold level to decide the closest match of an incomplete input is proposed.

Superior real-time holographic storage properties in doped potassium sodium strontium barium niobate crystal.

We demonstrate superior holographic storage performance in a cobalt doped potassium sodium strontium barium niobate (Co:KNSBN) crystal that possesses a fast response time of 1.4 ms, a large photorefractive sensitivity of 13 x 10(-3) cm(3) J(-1) under a total writing intensity of 1 W/cm(2) , and high spatial resolution of 45 line pairs/mm. Reconstructed images with high fidelity have been obtained in real-time holographic storage. The dynamic properties of the index grating, the dependence of response time on writing intensity, and the dark decay of diffraction signal with increased writing intensity indicate that two species and shallow traps exist in Co:KNSBN crystal.

Real-time edge-enhancement using self-pumped phase conjugation in BaTiO3

Abstract A new method using self-pumped phase conjugation to realize the edge-enhancement is presented. A theoretical explanation about this phenomenon is given.

Enhanced self-pumped phase conjugation from 16°-cut KNSBN:Cu

With the maximum coupling coefficient and high internal reflection conditions, the self-pumped phase-conjugation reflectivity of copper-doped potassium sodium strontium barium niobate (KNSBN:Cu) is increased with 16 degrees -cut samples. The response time is also shortened. The resolution property of 16 degrees -cut KNSBN:Cu is determined and a distorted image is corrected by using the 16 degrees -cut sample.

Kinetics of the higher-order response of photorefractive materials

The analytic expressions for the first three higher-order harmonics of the space-charge field versus time are obtained by use of the hopping model of Feinberg [J. Appl. Phys.51, 1297 (1980)]. The results are valid for arbitrary strengths of characteristic fields in the photorefractive materials with arbitrary values of the modulation depths. The dependence of the fundamental space-charge field on the higher-order fields is strong as the modulation depth increases. There is an apparent peak that originates from the contributions of the higher-order harmonics during the evolution of the fundamental harmonic of the space-charge field. We also determine the next-order correction to the fundamental space-charge field, which indicates that the ratio of the next-order correction term to the fundamental term is strongly dependent on the modulation depths m.

PERTURBATIVE ANALYTICAL SOLUTION OF TWO-WAVE COUPLING IN PHOTOREFRACTIVE MATERIALS AT LARGE MODULATION DEPTH

We apply directly a perturbative expansion to the hopping model of Feinberg. The first three harmonics of the space‐charge field are presented, considering the contributions from the higher‐order terms at large modulation depth. The dependence of the harmonics on spatial frequency, modulation depth and applied field strength are discussed. An analytical solution of the two‐wave coupling equations is given in this case. The mixing gain γ is also discussed.

Photorefractive two-wave mixing of rapidly phase modulated signals

Abstract We analytically solve the steady-state coupling equations of photorefractive two-wave mixing with a rapidly phase modulated signal for an arbitrary complex coupling constant without the undepleted pump assumption. It shows that the imaginary part of the coupling constant also contributes to the energy transfer in photorefractive two-wave mixing though the time average output intensity is only determined by the real part of the coupling constant. The energy transfer may exist even when the real part of the coupling constant is zero. The photorefractive two-wave-mixing with high-speed sinusoidal phase modulation is discussed in detail.