在LiNbO3∶Fe晶体中写入与存储圆形和环形波导

在光生伏打、自散焦光折变介质LiNbO₃∶Fe晶体中写入并存储了圆形与环形波导，并观察到了环形波导之间的相互作用.这种写入波导的方法和技术具有良好的应用前景. 关键词：     

在LiNbO_3∶Fe晶体中写入与存储圆形和环形波导

在光生伏打、自散焦光折变介质ＬｉＮｂＯ３∶Ｆｅ晶体中写入并存储了圆形与环形波导，并观察到了环形波导之间的相互作用．这种写入波导的方法和技术具有良好的应用前景．     

LiNbO3∶Fe晶体中光写入阵列平面光波导的实验实现

采用两束相干平行光形成的干涉光场辐照LiNbO3∶ Fe晶体,通过光折变效应在晶体中写入了阵列平面光波导.分别采用马赫-曾德干涉仪光路和光栅衍射法测量了阵列平面光波导的横向折射率分布和周期,并对所写入的阵列平面光波导进行了初步的导光测试.实验结果表明,用这种方法写入阵列平面光波导简便可行.     

LiNbO3:Fe晶体中光写入阵列平面光波导的实验实现

采用两束相干平行光形成的干涉光场辐照LiNbO₃: Fe晶体,通过光折变效应在晶体中写入了阵列平面光波导.分别采用马赫-曾德干涉仪光路和光栅衍射法测量了阵列平面光波导的横向折射率分布和周期,并对所写入的阵列平面光波导进行了初步的导光测试.实验结果表明,用这种方法写入阵列平面光波导简便可行.     

光生伏打LiNbO3:Fe晶体从自散焦到等效“自聚焦”的动态转换

实验研究了在一定条件下LiNbO₃:Fe晶体中从自散焦到等效“自聚焦”转换的动态行为,提出了出现自聚焦的物理机理为双相位共轭的法布里珀罗干涉腔中的多光束干涉与光折变效应的共同结果.该效应有希望在光折变自散焦介质中形成亮空间孤子 关键词： 自散焦 自聚焦 光折变     

部分空间非相干暗光伏孤子诱导一维波导研究

在光折变晶体LiNbO3∶Fe中观察到部分空间非相干光形成的一维暗光伏孤子,并由此暗光伏孤子在该晶体中诱导出一维波导.暗光伏孤子是由光折变晶体的强光伏效应产生,是晶体自散焦效应和衍射效应相平衡的结果；此外,光伏孤子的形成还依赖于光束的传播方向和晶体光轴与强度梯度的相对方向.在一维情况下,非相干光孤子诱导出单一的平面波导,能够对弱光敏的强光进行导光.实验证明了用低能量非相干光束控制转换高能量相干光束的可能性.     

光生伏打LiNbO_3:Fe晶体从自散焦到等效“自聚焦”的动态转换

实验研究了在一定条件下LiNbO3:Fe晶体中从自散焦到等效“自聚焦”转换的动态行为 ,提出了出现自聚焦的物理机理为双相位共轭的法布里 珀罗干涉腔中的多光束干涉与光折变效应的共同结果 .该效应有希望在光折变自散焦介质中形成亮空间孤子     

波导光折变功能光栅的研究

提出一种新的波导光折变功能光栅制作技术,利用导波光与空间光干涉,在Ｔｉ：ＬｉＮｂＯ３条形波导中通过光折变效应形成波导功能光栅,该方法也适用制作浮雕型波导光栅,用该方法,可制备周期小于二分之一光波长的光栅,并可灵活地调节波导功能光栅的形成与工作波长。     

非相干耦合热电光伏光折变空间孤子对(英文)

基于无偏压光伏光折变晶体,理论研究了热电效应和光伏效应共同作用下的稳态空间孤子对.从非相干耦合波方程出发,推导了热电光伏孤子对的数值解;采用有限差分方法,数值模拟了各类孤子对的强度包络.结果表明:在自散焦光伏光折变晶体中,当正的热电场远大于光伏场时,亮-亮孤子对可以存在;当暗-暗或者灰-灰孤子对存在时,负的热电场可以增强自散焦效应,进而减小孤子的半峰全宽.各类孤子对的半峰全宽可以通过改变热电场的大小而加以操控.此外,非相干耦合热电光伏孤子对可以在一定条件下分别退化成热电孤子对或者光伏孤子对.借助晶体的热电效应,可以使光折变晶体LiNbO3从自散焦转变成自聚焦,从而灵活控制晶体中孤子对的特性.     

光生伏打-光折变介质中光学涡旋孤子

简化了描述光生伏打光折变效应的模型方程.给出了光生伏打空间电荷场的形式解.讨论了单光束在光生伏打、自散焦光折变介质(LiNbO3∶Fe晶体)中的三维传播行为.指出在适当近似条件下,光生伏打光折变非线性可以维持圆对称的涡旋孤子. 关键词：     

Beaming effect in multimode photonic crystal by using coupled waveguides

Beaming effect of a multimode photonic crystal (PC) covered by a waveguide array on the exit plane is investigated theoretically. The simulation results show that the multimode PC can make the incident light split into two beams, which can be regarded as secondary sources radiating light into the waveguide array. As a result, many light beams can be generated in the array by the coupling among the waveguides, and the interference of these light beams after passing the system leads to directional emission. Additionally, the directional emission is greatly affected by the beam distribution on the exit plane of the system. Once the main light beams are formed on the exit plane of the system by modulating the system size, steady beaming effect can be obtained in the horizontal direction.     

Experimental realization of highly efficient broadband coupling of single quantum dots to a photonic crystal waveguide

We present time-resolved spontaneous emission measurements of single quantum dots embedded in photonic crystal waveguides. Quantum dots that couple to a photonic crystal waveguide are found to decay up to 27 times faster than uncoupled quantum dots. From these measurements beta-factors of up to 0.89 are derived, and an unprecedented large bandwidth of 20 nm is demonstrated. This shows the promising potential of photonic crystal waveguides for efficient single-photon sources. The scaled frequency range over which the enhancement is observed is in excellent agreement with recent theoretical proposals taking into account that the light-matter coupling is strongly enhanced due to the significant slow-down of light in the photonic crystal waveguides.     

基于二维光子晶体点缺陷可调谐光功率分配器

在二维矩形阵列结构硅光子晶体中去除中间一排硅柱形成线波导,在线波导右侧引入点缺陷。利用时域有限差分法(FDTD)模拟仿真以及数值分析研究线波导中光耦合特性,计算出两个通道的分光比,发现改变光子晶体的温度可以明显改变这两个通道的光功率比。基于此结构,提出了一种新的光功率分配器,可以获得大范围的光功率比值,从1∶1～90∶1都可以通过改变光子晶体的温度来实现,并且当温度从0℃～200℃就可以实现这一功能,最后设计了一款三通道可调谐光功率分配器,通过调节两个点缺陷区域内温度来实现光功率的分配。     

2D FDTD simulation of low loss small angle bend and Y branch configurations in a photonic crystal waveguide layout with a Mach–Zehnder device design configuration

A technique to produce low loss small angle bends in photonic crystal waveguides is presented. The technique consists of bridging parallel input and output waveguide segments with an inclined waveguide region of the same basic design that has a lateral dielectric shift. Results are presented for waveguides produced by enlarging the silicon gap along the central line, separating air holes in a square array photonic crystal for the TE polarization and an operating wavelength of λ_o = 1.55 μm. This low loss waveguide bending technique is applied to the design of Y branch and Mach–Zehnder photonic crystal structures. Simulation of the performance of the dielectric structures is achieved using 2-D FDTD, similar results are anticipated when applied to 3-D waveguide configurations and for other photonic crystal layouts.     

Self-focusing and defocusing in waveguide arrays

We show that two regimes of diffraction exist in arrays of waveguides, depending upon the input conditions. At higher powers, normal diffraction leads to self-focusing and to the formation of bright solitons through the nonlinear Kerr effect. By slightly changing the input conditions, light experiences anomalous diffraction and is nonlinearly defocused. For the first time, self-focusing and self-defocusing have been achieved for the same medium, structure, and wavelength.     

New version of seven wavelengths demultiplexer based on the microcavities in a two-dimensional photonic crystal

A new two dimensional photonic crystal demultiplexer of wavelength (WDM) is designed by exploiting two Fabry–Pérot reflectors at the end of the bus waveguides. The results show that the light with different wavelengths can be successfully filtered to different ports by setting different radius of the center defect rods in the drop waveguides and high drop efficiency can be achieved by means of reflection feedbacks. The proposed filter has a cross section equal to 9.7 μm × 5.8 μm. In the designed filter, an improvement of the number of channels has been achieved. The normalized transmission spectra of this component have been studied using finite difference time domain (FDTD) method. The important parameters consider for this studies are radius of rods used in Fabry–Pérot reflectors, and radius of center defect rods in the drop waveguides. The demultiplexer we designed can easily separate the light with seven different wavelengths simultaneously. The scope of this paper lies on demultiplexer for communication systems around 1.55-μm wavelength.     

Observation of modulational instability in discrete media with self-defocusing nonlinearity

We report what we believe is the first observation of modulation instability in the anomalous-diffraction regions of a photonic lattice. The experiments were carried out in a 1D waveguide array fabricated in a lithium niobate crystal displaying the photovoltaic self-defocusing nonlinearity, and our results are confirmed numerically by simulating the nonlinear beam propagation.