利用单模光纤中SBS效应进行被动调Q的掺铒光纤激光器研究

分析了利用光纤中的受激布里渊散射(SBS)相位共轭效应进行激光腔内调Q,产生ns量级脉冲激光的原理,并对利用该效应产生的激光脉冲波形和脉冲形成过程进行了数值模拟,得到的脉冲波形与SBS相位共轭反射率随时间变化曲线基本一致,表明利用光纤中的SBS相位共轭作用调Q具有可行性。据此,对采用单模光纤(SMF)作为SBS池的掺Er3＋调Q光纤激光器进行实验研究,当单模光纤长度为1.5 m时,在45 mW的抽运光功率下得到脉宽约2.6 ns,脉冲周期58.23 ns,平均功率7.35 mW的激光脉冲。进一步的研究表明：激光器中相位共轭镜的形成与SBS介质长度有关,SBS介质过长,斯托克斯线之间无固定的相位关系,不能形成相干叠加,SBS相位共轭腔不能形成; SBS介质过短,腔内正交偏振模光子寿命的改变使脉冲出现双峰现象。脉冲形成后其属性只与SBS动态属性有关。     

基于光纤中SBS相位共轭的自调Q光纤激光器

分析了利用光纤中的受激布里渊散射(stimulated Brillouin scattering,SBS)相位共轭效应进行激光腔内调Q,产生ns量级脉冲激光的原理,并对利用该效应产生的激光脉冲波形和脉冲形成过程进行了数值模拟,得到的脉冲波形与SBS相位共轭反射率随时间变化曲线基本一致,表明利用光纤中的SBS相位共轭作用调Q具有可行性.据此,对采用单模光纤(single-mode fiber,SMF)作为SBS池的Er³⁺掺杂调Q光纤激光器进行实验研究.当单模光纤长度为1.5 m时,在45 mW的光抽运功率下得到脉宽约2.6ns,脉冲周期58.23ns,平均功率7.35mW的激光脉冲.进一步的研究表明:激光器中相位共轭镜的形成与SBS介质长度有关,SBS介质过长,斯托克斯线之间无固定的相位关系,不能形成相干叠加,SBS相位共轭腔不能形成;SBS介质过短,腔内正交偏振模光子寿命的改变使脉冲出现双峰现象.脉冲形成后其属性只与SBS动态属性有关.     

Beam Combination using Stimulated Brillouin Scattering for the Ultimate High Power-Energy Laser System Operating at High Repetition Rate over 10 Hz for Laser Fusion Driver

After the laser was invented in 1960, a phase conjugation mirror has been respected to be the most fantastic one for the laser resonator composition because it can compensate any distortions of the laser beams occurred by the many inhomogenuities of the laser media and optical components. Among the many phase conjugation configurations, the stimulated Brillouin scattering phase conjugation mirror is the most simple one and many researchers have tried to utilize it to develop high power/energy laser systems. For realizing a high energy/power laser system the thermal problem is the most difficult to solve, and some researchers suggested a beam combination technique to reduce the thermal load of the big laser media to many small sized ones. To accomplish the beam combination using stimulated Brillouin scattering phase conjugation mirrors (SBS-PCMs), it is necessary to lock/control the phases of the SBS-PCMs. And some researchers have developed several ways for it, but they can lock the phases of a limited number of beams overlapped at the foci less than 5, or lock the phases by back-seeding technique but it loses the phase conjugation characteristics. For realization of the laser fusion driver, it is necessary to combine more than 10 or 100 beams. And the authors have developed recently a new phase controlling/locking technique which is isolated and independent totally from other beams and it can be applied to an unlimited number of beams in principle.     

Optical phase conjugation by resonant degenerate four-wave mixing in liquid phase medium

In this paper, frequency-doubled Nd:YAG laser's phase conjugation has been investigated experimentally using resonant degenerate four-wave mixing (DFWM). The iodine solution was used as resonant medium. In this way, the energy of the DFWM phase conjugation beam arrived at 43μJ/pulse while the total pump beam's energy reached 8mJ/pulse. The relation between the pulse energy of the DFWM phase conjugation beam and that of the pump beam was investigated. We also measured the optical field distributions of pump beam and DFWM phase conjugation beam, from which it can be noticed that the DFWM phase conjugation can improve the laser beam quality. At the same time, we observed the influence of the pump beam's disturbance on the DFWM signal.     

调Q激光光折变自适应光外差探测技术研究

基于光折变晶体中自泵浦与互泵浦相位共轭共存效应,利用新型光折变自适应光外差探测系统进行了调Q脉冲激光的光折变自适应光外差探测技术研究.结果表明,该系统可以用来实现单纵模调Q脉冲激光的自适应光外差探测,并可以通过提高本振光强度有效地提高外差探测灵敏度.进一步的实验和理论分析表明,对于一般的调Q脉冲激光,由于其各个纵模频谱分量之间不相关,难于实现光外差探测.     

偏振相移与相位共轭结合的散射光聚焦技术研究

散射介质对光的随机散射作用是制约其光学聚焦和成像的重要因素，光学相位共轭技术能够通过对散射光场共轭还原实现透过散射介质的光学聚焦和成像，其中散射光场相位的获取是共轭还原的核心。阐述了偏振相移的基本原理，将偏振相移与相位共轭技术相结合，设计了新的基于偏振相移的数字光学相位共轭系统。采用633 nm的HeNe激光器作为系统光源，毛玻璃作为散射介质开展散射光聚焦实验研究。实验结果表明:该装置能够成功实现透过散射介质的光学聚焦，其中聚焦点与背景光强的比值可达约400倍。     

飞秒脉冲放大器中色散的计算和评价方法

用光线追迹法论证了光栅球面镜系统与普通的光栅对系统是一对相位共轭元件,并提出了光栅球面镜系统色散的解析计算公式,以及对一个典型的放大系统做了模拟.模拟结果表明,对于一个放大系统,存在一个最佳的材料色散,用它可以获得最大的无色散带宽. 关键词： 飞秒激光放大器 展宽器 压缩器 色散补偿     

Wave phase conjugation of the stokes component of Brillouin scattering of ultrasound

Wave phase conjugation of a low-frequency ultrasonic wave due to Brillouin scattering of high-frequency parametrically phase conjugate waves in liquid was theoretically and experimentally studied. It was shown that the envelope of the low-frequency conjugate wave is proportional to the product of envelopes of high-frequency waves. The conjugation efficiency corresponds to the angular diagram of the resonant interaction of ultrasonic beams. Compensation for the phase shift of the plane low-frequency wave due to its wave phase conjugation was demonstrated.     

激光二极管列阵泵浦的位相共轭板条YAG激光放大系统

采用新型的微通道冷却半导体激光二极管列阵泵浦ＹＡＧ激光振荡器及板条ＹＡＧ放大器，文中用ＣＣｌ４受激布里渊散射作位相共轭镜，使激光在板条放大器中作多通放大，获得了高重复率下小于１．５倍衍射极限的高质量１．０６μｍ的激光输出，其脉冲宽度为１５ｎｓ，平均功率为１８０Ｗ。     

环形自泵浦相位共轭振荡器

本文报道由环形自泵浦相位共轭振荡器(采用 KNSBN:Ce 晶体)所产生的相位共轭波和47%的自泵浦反射率以及在这一装置中还观测到利用晶体缺陷对光的散射作用使变弱的共轭波增强,衍射光环增亮.     

积分球腔内BaTiO3：Ce晶体的自泵浦相位共轭增强现象的观测

报道了聚四氟乙烯积分球腔内光折变晶体ＢａＴｉＯ３：Ｃｅ在Ｈｅ－Ｎｅ激光作用下产生自泵浦相位共轭的增强现象，并对实验结果进行了分析。     

晶体几何结构及入射角度对自抽运相位共轭特性影响的研究

基于两块不同尺寸的Cu∶KNSBN晶体自抽运相位共轭实验,研究了光折变晶体的几何结构及入射角度对自抽运相位共轭特性的影响,得到在入射位置不变化的情况下,随着入射角度的变化相位共轭光输出有最大值,几何结构不同对应的最大值不同。并从理论上分析了晶体结构及入射角度在双作用区自抽运相位共轭机理中的作用,指出几何结构、入射角度与自抽运光通道、耦合系数的关系,及在自抽运相位共轭效应中存在一个最佳入射角度,这时相位共轭光输出最大。最后,对理论上的相位共轭反射率公式进行了修正。对自抽运相位共轭实际应用中,选择最佳入射角度提供了理论和实验依据。     

Ce：KNSBN晶体中产生的双泵浦相位共轭

首次报道在Ｃｅ：ＫＮＳＢＮ晶体中产生的“双”泵浦相位共轭现象，同时还观察到由同一“双”泵浦相位共轭光路所产生的自泵浦相位共轭和四波混频现象。     

Beam couplings and phase conjugate effects in reflection and transmission in BaTiO3

The details of experiments showing the effects of self-pumped phase conjugation on reflection and on transmission in barium titanate crystal are given. The specular reflection and the second-surface reflection of an extraordinary polarized beam, incident on the face of the crystal parallel to itsc-axis, get reduced in intensity as the phase conjugation develops. It has been found that parts of the self-pumped phase conjugate beam emerge out of the crystal as additional transmission beams. They grow in intensity as the phase conjugation develops. Other measurements which combine coherent or incoherent coupling beams are presented and used to explain the observations.     

Photorefractive Multi-Beam Induced Phase Conjugation

We demonstrate the simultaneous phase conjugation of multiple beams incident on the a face of a photorefractive barium titanate crystal. The input beam power, angle and position were set so that no phase conjugation occurs unless a switchable incoherent inducing beam is present on the — c face of the crystal. The use of the inducing technique with two mutually pumped phase conjugations for four input beams, or one self-pumped and one mutually pumped phase conjugation for three input beams can be performed in a crystal. Unlike the setup of conventional phase conjugation, which requires more precise arrangements, the novel setup of the multi-beam induced phase conjugation is relatively relaxed. The mechanism responsible for our discovery is qualitatively explained, and possible applications are mentioned.     

带受激布里渊散射相位共轭镜的Nd:YAG激光器

应用液体中受激布里渊散射相位共轭镜,与普通反射镜一起构成位相共轭谐振腔,得到了能量在10OmJ以上,脉宽在15ns以下的激光脉冲输出。实验测量了各种腔结构参数对输出能量的影响,并用相位板对该腔干扰,测量了其补偿特性。     

Four-wave mixing in semiconductor laser amplifiers: Applications for optical communication systems

Four-wave mixing in semiconductor laser amplifiers enables various applications in photonic switching including wavelength conversion, space and time switching, optical phase conjugation, and demultiplexing. Switching times faster than 1 ps are possible.     

Parametric phase conjugation for the second harmonic of a nonlinear ultrasonic beam

The effect of phase conjugation for the second harmonic of a focused ultrasonic beam was investigated experimentally and by numerical simulation. An ultrasonic pulse with the carrier frequency f=3 MHz was emitted into water and focused at a point between the source and the phase conjugating system. The phase conjugation for the second harmonic of the incident wave (2f=6 MHz) was performed in a magnetostrictive ceramic as a result of the parametric interaction of the incident wave with the pumping magnetic field (the pumping frequency was f_p=4f=12 MHz). The axial and focal distributions of sound pressure in the incident and conjugated beams were measured using a broadband PVDF membrane hydrophone. The corresponding calculations were performed by solving numerically the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation allowing for the nonlinearity, diffraction, and thermoviscous absorption. The results of measurements agreed well with the calculations and showed that the field of a conjugate wave adequately reproduces the field of the second harmonic of the incident wave. A certain advantage of focusing with the phase conjugation for the second harmonic was demonstrated in comparison with the operation at the doubled frequency of the incident wave. The results of this study can serve as a basis for the utilization of the phase conjugation of harmonics in ultrasonic tomography and nondestructive testing.     

Cu:KNSBN晶体自泵浦与互泵浦相位共轭共存特性的实验研究

利用Cu:KNSBN晶体,研究了在两束泵浦光对称入射的条件下,自泵浦与互泵浦相位共轭共存时相互竞争和相互影响的特性,以及共存时的相位共轭特性与两束泵浦光的入射位置、入射夹角和泵浦比之间的关系,并对自泵浦相位共轭反射率和两束泵浦光共同存在条件下的自泵浦相位共轭反射率进行了比较.     

Stimulated Brillouin scattering phase conjugating properties of long multimode optical fibers

This paper describes and characterizes a detailed experiment that proves the phase conjugating properties of stimulated Brillouin scattering in multimode fibers (km of length), a problem still in debate in the literature, by studying the random aberrations correction abilities of this nonlinear interaction. Detailed qualitative and quantitative evaluation of aberration correction, by using the M² beam propagation ratio as a criterion to assess beam quality of the beams, proves the phase conjugation via SBS in long MM fibers. A new parameter to characterize the efficiency of the SBS phase conjugation process is proposed and conditions to obtain a complete healing of distortions (complete phase conjugation) are discussed.