非线性环形光学腔中分岔混沌的新行为

利用数值模拟方法研究了非线性环形光学腔中的Ikeda方程,发现:长延时下,分岔图的拓扑结构、分岔方式、收敛速率以及周期窗口的结构都随参数B,φ₀的取值不同而异。短延时下,通过适当近似,将Ikeda方程化为带有一定记亿效应的迭代映象,所得到的近似系统显示出非倍周期分岔行为,并伴有一些奇特的周期窗口,混沌区中的无限嵌套的自相似结构变得模糊,不易分辨。 关键词：     

Optical soliton with group delay in microring coupled-resonator optical waveguides

This paper derives the dispersion relation of microring coupled-resonator optical waveguides (CROWs) without any approximation by using the transfer matrix method. Based on the established dispersion relation of CROWs it obtains the slow group velocity and dispersion coefficient. It finds that the effect of dispersion on optical pulses can be adjusted to balance the effect of nonlinearity by changing coupling coefficient or loss, so optical soliton with group delay can be obtained in microring CROWs. The optical soliton with group delay is of great significance for applications of microring CROWs in delay lines and optical buffers of future all-optical communication systems.     

Pulse delay at diffractive structures under resonance conditions

An optical pulse incident upon a diffractive structure under resonance conditions may undergo a temporal delay. The effect is demonstrated with a pulse of Gaussian profile at two geometries: a waveguide grating and a single-mode waveguide. It is shown that the order of magnitude of the delay can be controlled by the parameters of the structures.     

Impact of chromatic dispersion and group delay ripple on self-phase modulation based optical regenerators

We demonstrate that chromatic dispersion and group delay ripple limit the performance of all-optical regeneration based on self-phase modulation. The level of degradation depends in detail on the type of phase distortions introduced. The regenerator performance is measured using the optical signal to noise ratio (OSNR) margin provided to the system for a given bit error ratio. The addition of chromatic dispersion and group delay ripple induces a significant reduction in this OSNR margin.     

Compact photonic delay line constructed by holographic optical elements

To fully support phased-array antenna and other applications, a 3-range (long time, moderate time, and short time) delay line structures with holographic optical elements is proposed. Flexibility, light-weight, on-axis coupling, easy alignment, easy fabrication, and compactness are their advantages. When use holographic optical elements to build the photonic delay line system, all of the delay and non-delay paths in these three photonic delay lines are setting in a compact structure. They do not need any extra components, such as mirrors and optical paths in free space, and can bear stronger vibration. Therefore, the holographic optical elements are more suitable to design the photonic delay lines. In these three structures, their losses and crosstalk s are balanced. All of delay and non-delay cases in these three delay line structures, their crosstalk, signal-to-noise ratio, and loss are 1/81,000, 59.1 dB, and 3.2 dB, respectively. Finally, to support complete applications, a polarization independent photonic delay line system with holographic optical elements is proposed, too.     

Integrated optical delay lines:a review and perspective[Invited]

Optical delay lines(ODLs) are one of the key enabling components in photonic integrated circuits and systems.They are widely used in time-division multiplexing, optical signal synchronization and buffering, microwave signal processing, beam forming and steering, etc. The development of integrated photonics pushes forward the miniaturization of ODLs, offering improved performances in terms of stability, tuning speed, and power consumption. The integrated ODLs can be implemented using various structures, such as single or coupled resonators, gratings, photonic crystals, multi-path switchable structures, and recirculating loop structures.The delay tuning in ODLs is enabled by either changing the group refractive index of the waveguide or changing the length of the optical path. This paper reviews the recent development of integrated ODLs with a focus on their abundant applications and flexible implementations. The challenges and potentials of each type of ODLs are pointed out.     

Spatial uniformity of group delay in the IR diode radiation attained by short segment of optical fibre application

A simple method for obtaining high uniformity of group delay in the IR diode radiation by means of a short segment of optical fibre attachment is decribed and the results are presented.The experiments were done with edge emitting IR diode structures of over 3 ns ascertained group delay spatial inhomogeneity which, after application of the optical fibre decreased to below the 0.1 ns level.     

Full-range tunable optical delay line based on coupled and side-coupled resonators

An optical delay line based on a new kind of structure comprising coupled resonators and side-coupled resonators has been proposed and demonstrated. The structure has unique advantages in realizing tunable optical delay lines. The tuning range has covered almost the full range of the optical delay line, from minimum delay at which only one ring of the light pulse structure requires transmission, to maximum delay at which all rings are required. In addition, the input signal delivered from the input to output port travels the structure twice, thereby providing buffer delay that is twice longer than general coupled resonators.     

可实现偏振无关单向传输的二维硅基环形孔光子晶体

基于光子晶体来构筑偏振无关光二极管在光电集成领域具有重大的应用价值.首先提出了一种环形孔光子晶体,能带结构显示其对横电及横磁模式同时展现出显著的方向带隙.以此构建了三角形状的环形孔光子晶体,利用时域有限差分法计算其透过谱及场分布图,发现该结构能实现偏振无关单向传输特性,然而正向透过率太低(约20%).进一步引入尺寸较小的三角形状的环形孔光子晶体构成光子晶体异质结结构,有效地提高了偏振无关单向传输性能,正向透过率增大了一倍.通过界面结构的调整,正向透过率进一步增大,优化后的环形孔光子晶体异质结结构能同时对类横电及类横磁模式入射光实现单向传输,且正向透过率达到了44%.     

Focusing surface plasmon polariton wave packets in space and time

The spatiotemporal focusing of surface plasmon polariton (SPP) wave packets (WPs) by planar plasmonic‐lens coupling structures is described using combined femtosecond interferometric time‐resolved photoemission electron microscopy (ITR‐PEEM) imaging and model simulations. The focusing properties of lens structures inscribed lithographically into Ag films depend on the angle of incidence of the excitation field. Severe aberrations are introduced by the phase delay in the interaction of obliquely incident plane waves with the commonly employed circular arc‐shaped lens structures. It is shown that the aberration can be corrected by accounting for propagation delays caused by the incidence angle‐dependent retardation of the optical field‐lens structure interaction. The focusing of SPP‐WPs in both space and time is demonstrated with aberration corrected lens structures.     

Conformal and projective structures in general relativity

It is proposed that compatible conformal and projective structures be taken as the basic space-time structures in general relativity, with the symmetry group restricted to unimodular diffeomorphisms. Models of classical massless fields, such as the Maxwell field, interact directly with the conformal structure; while classical bodies composed of massive particles, such as solids and fluids, interact directly with the projective structure. It is suggested that this difference is the classical limit of the respective quantum-gravitational interactions, which should reflect the differing approaches to the quantization of fields and particles when gravity is neglected. Models of general relativity based on compatible conformal and projective structures should be the basis for the exploration of ideal measurement procedures, both classical and quantum.     

啁啾双光纤光栅群时延特性

研究了变迹线性啁啾双光纤光栅的群时延特性及其在高次色散补偿中的应用.分析表明,群时延特性与周期差ΔΛ和不同的啁啾参量C有很大的关系.研究结果表明啁啾双光纤光栅在高次色散补偿和光纤CDMA中有应用价值.     

Sensitivity-bandwidth product for electro-optic modulators

For lumped-element electro-optic modulators, the sensitivity ( partial differentialphi/ partial differentialV) of the phase, phi , in response to an applied voltage V is related to the optical group delay, T(g) , and the bandwidth, Domega . This relationship imposes a fundamental trade-off between the sensitivity and the bandwidth of electro-optic modulators: ( partial differentialphi/ partial differentialV)Domega= (dn/dV)(omega /n) , where n is the optical index. A similar relationship for traveling-wave modulators sets an upper limit on ( partial differentialphi/ partial differentialV) that is proportional to T(g) .     

Dynamics of fractional-ordered Chen system with delay

In the present paper the effect of delay on chaos in fractional-order Chen system is investigated. It is observed that inclusion of delay changes chaotic behaviour to limit cycles or stable systems.     

Control of slow light in a ring-out-ring structure

This paper proposes a ring-out-ring structure of coupled optical resonators to yield coupled-resonator-induced transparency (CRIT). Considering the insertion loss of the coupler,it theoretically deduces the transmission and the effective phase shift. The influences of the insertion loss of the coupler on the transmittance,the effective phase shift,the group index and the CRIT linewidth are fully studied. We find that the increase in multiple m can effectively enhance the normal dispersion and the group index of the proposed structure. Moreover,the specific expression of the group index at resonance is theoretically deduced and discussed for the proposed structure with two rings. The result shows that the multiple m between the lengths of ring 1 and ring 2 can enhance the group index to m times that of the structure with two equal-sized rings at resonance. The control of slow light in the proposed structure is important for applications of highly sensitivity gyroscopes,optical delay lines and optical buffers,etc.     

基于磁光开关的高精度光实时延时线

 给出了基于高速磁光开关的光实时延时技术的方案。研究了拓扑结构和磁光开关对光延时性能的影响。研制了5 bit,32位的光实时延时系统,并建立了光延时的测试平台,经测试,延时线延时精度优于3 ps。对光延时单元插损进行测试,结果显示:32态单元插损为0.12~0.88 dB,各态变化呈随机性。     

衍射散射式颗粒粒度测量法的研究新进展

介绍了衍射散射式颗粒粒度测量法的基本光路结构和理论模型,讨论了决定其性能优劣的重要指标--测量下限,对影响测量下限向小粒径范围延伸的参数进行了分析.继而介绍了近年来国内外主要粒度仪品牌在光学结构和散射理论模型方面所做的改进,阐述了它们的工作原理和性能特点.最后对衍射散射式颗粒粒度测量法的发展前景做出了展望,从修正理论模...     

Signal velocity, causality, and quantum noise in superluminal light pulse propagation

We consider pulse propagation in a linear anomalously dispersive medium where the group velocity exceeds the speed of light in vacuum ( c) or even becomes negative. A signal velocity is defined operationally based on the optical signal-to-noise ratio, and is computed for cases appropriate to the recent experiment where such a negative group velocity was observed. It is found that quantum fluctuations limit the signal velocity to values less than c.     

Spontaneous motion of localized structures and localized patterns induced by delayed feedback

We study the properties of 2D dissipative structures in a coherently driven optical resonator subjected to a delayed feedback. It has been predicted that delayed feedback can lead to the spontaneous motion of bright localized structures [M. Tlidi et al., Phys. Rev. Lett. 103, 103904 (2009)]. We study here the phenomenon in detail. In particular, we show that the delayed feedback induces a spontaneous motion of periodic patterns and dark localized structures. We focus our analysis on nascent optical bistability regime where the space time dynamics is described by a variational Swift-Hohenberg equation. In the absence of delayed feedback, dark localized structures and patterns do not move. This behavior occurs when the product of the delay time and the feedback strength exceeds some critical value.     

Dispersion and loss limitations on the performance of optical delay lines based on coupled resonant structures

The relative importance of group-velocity dispersion and loss-induced distortion in limiting the performance of optical delay lines based on coupled resonator structures is investigated. It is shown that for the current state of the quality of fabrication both factors play roughly comparable roles for bit rates of 2.5-40 Gbits/s and that as the storage capacity grows, the relative weight of loss-imposed limitation increases.