Multi-functional real-time optical processor with self-pumped phase conjugator of Cu:KNSBN

A multi-functional real-time optical processor with a self-pumped phase conjugator of Cu:KNSBN crystal is presented. The key device, self-pumped phase conjugator, has functions of both a mirror and a real-time recording medium in the processor.     

应用诱导互泵浦位相共轭镜的实时图像处理

利用自泵浦诱导的互泵浦位相共轭镜，在１６°切掺铜钾钠铌酸锶钡晶体中，分别对信号图像的完整输出和边缘增强输出实现了两幅图像的实时相加和相减处理。位相共轭输出的成像分辨率高达５０ｐｌ／ｍｍ。     

利用猫式自泵浦位相共轭镜的光学联想存储器

报道了以快速响应（１５０ｍｓ），成像质量高（分辨率＞５０ｐｌ／ｍｍ）的１６°切掺铜钾钠铌酸锶钡（Ｃｕ：ＫＮＳＢＮ）晶体猫式自泵浦位相共轭境作为取阈反馈器件，以低吸收薄晶体Ｃｅ：Ｆｅ：ＬｉＮｂＯ３作为存储介质的光学全息联想存储器，利用２５％原信息寻址，可得出完整的联想输出．     

Mutually pumped phase conjugator using a BaTiO3 crystal having two inclined faces

A pentagon-shaped undoped BaTiO₃ crystal was used to construct a high-quality mutually pumped phase conjugator. It yields two very stable phase-conjugate outputs (ǃ.7% fluctuation in intensity) with high reflectivity (the highest ᅝ%) when the two incident beams are of equal intensities. The response time of the conjugator is rather fast (ƻ s) and the tolerance of the acceptance angle is large too (걄°). Fine structures (35 7m) in an image, after passing through a phase aberrator, can be recovered by the conjugate waves yielded by this conjugator.     

KNSBN晶体猫式互抽动相位共轭光特性

在KNSBN：Ce晶体中，利用二波耦合作用，在单一光束无法获得相位共轭光的条件下，实现了“猫”式互抽运相位共轭光输出，获得较高的共轭光发射率，实验结果表明，晶体的二波耦合作用可以使晶体的自抽运相位共轭光的阈值光强降低。入射光的入射角范围增大，响应时间缩短。     

利用光感应自泵浦方法实现图象的色彩转换

首次报道一种利用光折变晶体的光感应自泵浦实现图象色彩转换的方法。用此方法可得到具有相位共轭的正转换图象,其分辩率可达到281p/mm,同样的方法可用于将非相干图象转换成相干图象。     

利用自泵浦相位共轭器对通过热晕池的扰动激光束的实验研究

利用光折变晶体的自泵浦相位共轭器，在稳态和动态条件下对通过扰动的热晕池的激光束质量进行观测，在动态实验研究中，采用了所谓的预置光栅的方法。     

Study of the Frog-legs Phase Conjugator in BaTiO_3

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Properties of cat mutually pumped phase conjugation and two-wave mixing gain in doped KNSBN

Cat mutually pumped phase conjugation configuration is discovered and investigated by using two-wave mixing in (KyNa1-y)2z(SrxBa1-x)1-zNb2O6 (KNSBN) crystal. When only one signal or pumped beam does not give birth to phase conjugation, the maximum reflectivity of signal and pumped beam attain 140% and 30% due to two-wave mixing, respectively. The experimental results show that the two-wave mixing can reduce the threshold of incident beams power, extend the incident angle range, and shorten response rate in the process of self-pumped phase conjugator (SPPC) in KNSBN crystal.     

Ce：BaTiO3晶体自泵浦相位共轭特性和机理研究

在Ｃｅ：ＢａＴｉＯ３晶体中，实现了受激折变散射自泵浦相位共轭，给出了其自泵浦相位共轭形成的特点以及相位共轭波输出特性。比较了不同波长的入射光对自泵浦的形成特点和共轭波输出特性的影响。     

实时图像反转与实时图像高低通滤波

报道了以Ｃｅ，Ｆｅ：ＬｉＮｂＯ３薄晶体作记录介质，利用Ｔｉ，Ｃｕ：ＫＮＳＢＮ晶体猫式自泵浦位相共轭镜供反向读出光新型实时光学处理器，该处理器可以实现图像反转，图像高，低通滤滤等操作。文中还给出了基于全息记录与擦除、自衍射与尺寸效应等的机理解释。     

非相干光作用下的Ce：BaTiO3自泵浦相位共轭镜特性

地Ｃｅ：ＢａＴｉＯ３晶体的自泵浦相位共竟然非相干光作用下自泵浦相位共轭反射率增强的特性进行了研究。实验是在Ｈｅ－Ｎｅ激光产生稳态自泵浦相位共轭输出后，用非相干光平行ｃ轴照射来获得这一增强特性的，当水平移动非相干光入射位置，发现有两个区域非相干光作用能使相位共轭反射率增加，本文对此进行了相应的分析和讨论。     

双光折变晶体半线性相位共轭器的自脉动

在由两块光折变BaTiO3晶体(其中一块晶体为全内反射式自抽运相位共轭镜工作方式,起外反射镜作用)构成的半线性自抽运相位共轭器中观察到了相位共轭光的自脉动现象。自脉动的平均频率f与入射光功率I0的关系为f∝I01.43;相位共轭光的平均维持时间ΔT与入射光功率I0近似成反比。观察到光折变BaTiO3晶体中扇形散射光具有动态的空间结构,扇形散射光的这种特性是引起上述半线性自抽运相位共轭器中相位共轭光脉动的原因     

Optical restoration of photorefractive holograms

We consider the possibility of restoration and/or enhancement of decaying holograms in photorefractive media by using a simple optical readout in conjunction with a phase conjugator. The results indicate that extremely weak holograms can be enhanced provided that the two-beam coupling is sufficiently strong. Steady-state photorefractive holograms can be maintained continuously without decay by using a self-enhanced readout scheme. The results also provide an explanation for the formation of mutually pumped phase conjugation in terms of the amplification of an initial noise grating. The results are presented and discussed.     

+c–face incident pentagon mutually pumped phase conjugator

The mutually pumped phase conjugator with +c-face incident geometry is first demonstrated in a photorefractive pentagon-shaped 0°-cut BaTiO₃ crystal. Designed by choosing the appropriate geometry such as the orientation between two mutual incoherent beams and the special cut crystals c-axis, a novel configuration can be formed in the crystal when the mutually pumped phase conjugation is established. This configuration provides more efficient interaction, which provides fast response and high stability as well as large angular acceptance and high image resolution. PACS 42.65.HW; 42.70.Nq     

Mutually Pumped Phase Conjugation of Three Incoherent Beams with a Novel Photorefractive Crystal

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Incident-angle dependence of the phase conjugate reflectivity by nonlinear piezoelectric interaction in PZT ceramics.

The reflectivity of an acoustic phase conjugator by nonlinear piezoelectric interaction in PZT ceramics was measured as a function of the incident angle. The phase conjugator was designed as a solid block with a flat surface for the acoustic incidence from water. The phase conjugate reflectivity showed incident angle dependence, which is mainly determined by the transmissivity of the acoustic waves, together with some effects of anisotropy. The field-reconstructing ability of this phase conjugator was simulated for focused incident beams.     

Dispersion compensation for a femtosecond self-pumped phase conjugator

Dispersion compensation for a photorefractive self-pumped phase conjugator with femtosecond pulses is analyzed. The self-pumped phase conjugator consists of a pair of dynamic gratings coupled by total internal reflections at the crystal surfaces (cat conjugator). The negative angular dispersions of refraction at the air-crystal interface and the gratings inside the crystal compensate for the positive dispersion of the finite crystal path. The experimental results show that with partial dispersion compensation the width of the self-pumped phase conjugation at 450 nm of femtosecond pulses is narrower than that of the transmitted pulses.     

Comments on Shakir's “zero-area optical pulse processing by degenerate four-wave mixing”

We disagree with one of the contentions of Shakir's paper, namely that a zero-area pulse can be generated by an unstable phase conjugator. We find, on the contrary, that any unstable conjugator would, if the pumps were not depleted, generate a conjugate wave of infinite area. We show by counterexample that the response generated by Shakir's technique is noncausal if the conjugator is unstable.     

Wavelength-stable, narrow-spectral-width oscillation of an AlGaInP diode laser coupled to a BaTiO3:Co stimulated photorefractive backscattering phase conjugator

3 ) stimulated photorefractive backscattering (SPBS) phase conjugator. The SPBS process was successfully achieved by the combination of the short-wavelength diode laser and the highly doped photorefractive BaTiO₃:Co crystal. The spectral width of the diode laser is reduced to 7.2 pm because of the narrow spectral bandwidth of the gratings [with wave number of K=2k(2k gratings)] formed in the SPBS phase conjugator, compared with the transmission grating formed in the conventional cat conjugator, which was used previously. The SPBS phase conjugator was successfully used to suppress self-frequency scanning, and wavelength-stable oscillation of the SPBS phase-conjugator-coupled diode laser was achieved. Received: 4 November 1996/Revised version: 12 February 1997