Analysis of a gained nonlinear directional coupler pulse switch

We have investigated the switching performance of a gained (nonlinear directional coupler) NLDC switch in the presence of both 2nd and 4th order gain nonlinearities. In this system, we have achieved a nearly complete pulse switching at half beat length of the coupler which implies about 40% reduction in the switching length as compared to the switching length reported in Trillo et al. (1988). We have shown that at the half beat length the output energy of each branch is equal to that of the input energy and hence the gained NLDC switches have ability to be cascaded. Our initial investigations reveal that this gained NLDC switch has remarkable performance and potential to be used in ultra-fast optical communication systems.     

闭路光伏灰孤子诱导的波导

理论分析了闭路光伏晶体中灰孤子诱导的波导.研究发现,闭路光伏灰孤子诱导的波导在不同孤子灰度值,电流密度和光强比率下均为单模,文中光强比率指孤子峰值强度与暗辐射之比.研究结果解释了闭路光伏灰孤子限制在中心的能量随着电流密度的增加而增加,随着孤子灰度值和光强比率的增加而减小.文章还提供了光伏晶体的相关例子.     

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.     

A new soliton communication band for optical networking redundancy using a Gaussian soliton generation

We present a novel communication band of the tunable multi-Gaussian soliton system, whereas the large bandwidth signals of the spatial soliton pulses can be generated after propagating within the nonlinear ring resonator system. A Gaussian pulse input with 20 ns pulse width, 2 W peak power, the center wavelength at 1300 nm is propagated into the nonlinear ring resonator system. Using the appropriate parameters relating to the practical device such as micro-ring radii, coupling coefficients, linear and nonlinear refractive index, we found that the multi-soliton pulse obtained have shown the potential of application for a new dense wavelength division multiplexing (DWDM) band. The soliton pulse width and free spectrum range of 400 and 7 fm are obtained, respectively, which can be used to increase the channel capacity in soliton communication. Furthermore, the soliton power obtained is available for system and link redundancy, where the output soliton power of 12 W is achieved.     

An investigation of dark soliton behaviors within the nonlinear micro and nano ring resonators

We firstly propose the interesting results of a dark soliton pulse propagating within the nonlinear micro and nano waveguides. The system consists of nonlinear micro and nano ring resonators, whereas the dark soliton is input into the system and traveling within the waveguide. A continuous dark soliton pulse is chopped to be the smaller pulses by the nonlinear effects known as chaos. The nonlinear behaviors such as chaos, bistability and bifurcation are analyzed and discussed. The power amplification is the property that can be used to perform the long distance link, where the security is the dominant reason.     

THz light pulse generated and storage by using a Gaussian pulse within a waveguide system

We propose the interesting results of high frequency generation method, which is required to use in the THz regime. A generated system consists of two micro and a nano rings that can be integrated into a signal system which can be employed to generate the large bandwidth by a Gaussian pulse propagating within the ring resonator system. The selected signals can be stored and filtered by using the optical storage unit and an add/drop filter, respectively. By controlling the ring parameters, the appropriate output power can be obtained, which can be modified to be suitable in either imaging or communication applications. Moreover, the very wide band of wavelength can be generated and controlled for various applications.     

Multi-channel 80-GHz RZ pulse train generation based on parametric process in highly-nonlinear fiber

It is experimentally shown that six-channel C + L-band 80-GHz short pulse trains are generated based on parametric process in highly-nonlinear fiber (HNLF). By launching a pulsed pump and three-channel continuous wave (CW) lights into 1-km HNLF, three-channel signals are amplified and three-channel idlers are generated. The waveforms of the generated 80-GHz short pulses are measured by an auto-correlator. The bit-error-rate (BER) of each channel is analyzed numerically. In the back-to-back case, the power penalties of the generated channels are less than 1.5-dB.     

Spectrum reshaping of amplified pulse in silicon nanowaveguide

A device consisting of a cascaded semiconductor optical amplifier (SOA) and silicon on insulator (SOI) optical waveguide is presented to amplify and reshape the frequency spectrum of optical pulses in the picoseconds time duration. Numerical simulations show that the output spectrum of the amplified pulse by SOA can be effectively reshaped by utilizing the SOI waveguide. The length of the SOI waveguide may be judiciously adjusted to significantly reduce the frequency chirp of the output pulse from the SOA resulting in reshaping of the output spectrum. We find that the property of pulse spectrum is sensitive to the input pulse power and its temporal width.     

一种用单模光纤制作亚微米周期光栅的方法

本文报道一种用单模光纤制作亚微米周期光栅的全息方法,并详细分析和讨论了影响光栅质量的各种因素。实践证明这一方法完全适于制作面积不小于10×10mm~2适于集成光学元件需要的高质量光栅。     

非线性对称平板光波导TE模色散特性的近似计算

本文利用微扰法,导出了克尔型非线性对称平板光波导TE模传播常数的近似计算公式。结果表明,本文公式得到的结果与精确结果吻合得很好。     

Optical properties of an off-center hydrogenic impurity in a spherical quantum dot with Gaussian potential

Optical absorption coefficients and refractive index changes associated with intersubband transition of an off-center hydrogenic impurity in a spherical quantum dot (QD) with Gaussian confinement potential are theoretically investigated. Our results show that the optical absorption coefficients in a spherical QD are 2–3 orders of magnitude higher than those in quantum wells and are 2–3 orders smaller than those in a disk-like QD. It is found that the optical absorptions and the optical refractive index are strongly affected not only by the confinement barrier height, dot radius but also by the position of the impurity.     

高斯光束计算平板波导自由传输区远场分布及其修正

对近轴近似条件下求解亥姆霍兹方程得到的高斯光束显式传播公式做了分析，同时，基于基尔霍夫衍射理论，在菲涅耳近似的条件下给出了相应的高斯光束在远场的传播公式，在此基础上，对近轴近似条件做出了定量分析，给出了这个近似条件引入的误差，提出了一种计算高斯光束远场分布的修正方法，并采用有限差分-光束传播方法(FD-BPM)来检验各种方法的准确性。把这种修正方法应用到平面光集成波导器件，如阵列波导光栅(AWG)、蚀刻衍射光栅(EDG)等器件的设计和模拟中，可以大大降低工作的复杂性，同时可以得到精确的结果。     

非线性光定向耦合器解的简化表达式

本文将非线性定向耦合器在任意输入情况的解进行了简化.在本文解的基础上,非线性光定向耦合器的工作点,即其开关、调制和放大应用(几乎所有应用)的输入条件能很容易地由解析式确定,并在理论上提出了非线性光定向耦合器一个新的应用:一束强光的相位可以由一束弱光的功率加以控制.     

Femtosecond pulse switching in a fiber coupler with third order dispersion and self-steepening effects

A numerical study of femtosecond pulse propagation and switching in a dual-core nonlinear directional coupler with the consideration of third order dispersion and self-steepening effects is reported. The Split Step Fourier Method (SSFM) is used to investigate the switching characteristics of nonlinear directional couplers. It is observed that the energy transfer from core to core is not affected by changing the input pulse shapes except super-Gaussian. While the normalized coupling co-efficient and the input peak power dominate the coupling characteristics, the effects of third order dispersion (TOD) and self-steepening (SS) are also reported.     

SOI及GeSi/Si脊形光波导的模式与波导几何结构

用有效折射率方法对SOI（绝缘体上硅）及GeSi/Si脊形光波导的单模条件进行了模拟,与Soref的单模条件进行了比较,将两者与实验结果进行了比较,得到了与实验结果符合得非常好的单模条件。同时对多模波导进行了模拟,得到了波导承载一阶和二阶模的条件。     

一种温度不敏感型阵列波导光栅的研究

研究了的一种新型温度不敏感型阵列波导光栅(AWG)。该新型温度不敏感型阵列波导光栅的波导采用混合材料的波导结构，该混合材料波导通过在石英波导芯层上旋涂聚合物材料的上包层，达到改变波导温度特性的目的，使得阵列波导光栅的温度敏感性降低。通过理论分析和有限差分方法研究了其中两种结构：三层混合材料波导构成的阵列波导光栅和四层混合材料波导构成的阵列波导光栅，计算了该新型温度不敏感型阵列波导光栅的温度特性。结果表明，在一定的设计下，温度变化0～50℃时，这两种温度不敏感型阵列波导光栅的最大波长漂移量小于0．03nm，不到无温度控制时常规阵列波导光栅最大波长漂移量的4％。     

波导短程透镜的实验研究

波导透镜是集成光路〔IO〕中的最基本元件,它在IO中的作用类似体光学光路中的透镜.IO光信号处理系统如集成光学声光频谱分析器、导波声光卷积器、相关器、调频脉冲压缩器和矩阵乘法器等.系统中都需要用波导透镜.波导短程透镜较其它形式的波导透镜具有孔径大、旋转对称、无色差和插入损耗小的特点,所以特别引人注意.     

Soliton switching study using new normalized nonlinear Schrödinger equations

Soliton switching in a nonlinear directional coupler (NLDC) is studied by using new normalized nonlinear Schrödinger equations (NLSE). The resulted equations have one parameter κL_D only, this feature greatly simplifies the numerical study of soliton coupling in a NLDC, and it enables us to derive the soliton switching conditions based on numerical analysis. Numerical results show that most of the input soliton energy remains in the launched waveguide when input soliton normalized peak power is bigger than 2.5. It is contrary to the existing theoretical expectations which were derived using variational approach. The fundamental soliton switching conditions is also expressed in terms of input soliton pulse width. In addition, it is found that frequency chirp degrades soliton switching performance in a NLDC.     

Priority-based parameter optimization strategy for reducing the effects of four-wave mixing on WDM system

In order to meet the ultra high speed and ultra long-haul transmission distance in wavelength division multiplexing (WDM) systems, the nonlinear impairment affecting the overall spectral efficiency and system performance should be minimized. This paper proposes a strategy to mitigate the four-wave mixing (FWM) effect in WDM system. The strategy determines the effect of both single and combined effects of second, third, and fourth optimization priority parameters such as fiber length, input power, dispersion, channel spacing, and effective area on FWM power. A comparison study was made under different types of optical fiber such as single-mode fiber (SMF), dispersion shifted fiber, non-zero dispersion fiber, and non-zero dispersion shifted fiber. In addition, the system performance in term of bit-error-rate was calculated in the case of single priority (impact of effective area) and combined priority (impact of effective area, input power, fiber length and channel spacing). The results show that the FWM effect was reduced based on the transmission parameters order of optimization, i.e., priority selection proposed. Moreover, the results indicated that increasing sequentially the effective area, fiber length; channel spacing and decreasing the input power provide the most significant sequence in suppressing the effects of FWM. This priority sequence brought the suppression ratio to approximately 26.3% in SMF, which suppressed the FWM effects up to −50 dBm. In term of BER; the combined priority introduces improvement in BER of 2.31 × 10⁻²⁵ in comparison with single priority that has value of BER 4 × 10⁻¹⁴. Finally, this work suggests that the proposed priority-based parameter optimization strategy is an ideal solution for optimum performance of WDM system.     

Self-trapped dynamics of a hollow Gaussian beam in metamaterials

We present a systematic investigation on the dynamics of a hollow Gaussian beam (HGB) in metamaterials. We predict self-trapped propagation of HGBs and evolution of the beam is highly influenced by dimensionless dispersion coefficient (κ), which determines the strength of dispersion over diffraction. The evolutions of HGBs such as disappearance of single ringed intensity pattern and appearance of patterns with a central bright spot are achievable with less propagation distance in metamaterials with higher values of κ. On the other hand, metamaterials with low values of κ can preserve single ring intensity distribution over a long propagation distance without focusing. When the strength of dispersion over diffraction increases, it significantly influences the evolution of the beam and may lead to the formation of tightly focussed beam with high peak intensity at the center. The phenomenon of tight focussing is found to have some applications in trapping of nanosized particles.