超快速光子晶体全光开关研究

光子晶体作为一种新型的人造光子学材料,具有独特的光子带隙特性,能有效地控制光子的传输状态,因而是实现全光开关等集成光子器件的重要基础。介绍了基于光子晶体的全光开关的各种实现方法,并详细论述了超快速光子晶体全光开关的实验研究状况。     

表面等离激元的操控:原理与研究进展

近年来表面等离激元在物理学、生物学等领域的应用有非常显著的进展. 本文针对表面等离激元在集成光路发展中的应用,重点介绍其传输、增益及传输损耗补偿、开关与调制等操控原理与特性等方面的研究进展.     

Large-scale synthesis of a silicon photonic crystal with a complete three-dimensional bandgap near 1.5 micrometres

Photonic technology, using light instead of electrons as the information carrier, is increasingly replacing electronics in communication and information management systems. Microscopic light manipulation, for this purpose, is achievable through photonic bandgap materials, a special class of photonic crystals in which three-dimensional, periodic dielectric constant variations controllably prohibit electromagnetic propagation throughout a specified frequency band. This can result in the localization of photons, thus providing a mechanism for controlling and inhibiting spontaneous light emission that can be exploited for photonic device fabrication. In fact, carefully engineered line defects could act as waveguides connecting photonic devices in all-optical microchips, and infiltration of the photonic material with suitable liquid crystals might produce photonic bandgap structures (and hence light-flow patterns) fully tunable by an externally applied voltage. However, the realization of this technology requires a strategy for the efficient synthesis of high-quality, large-scale photonic crystals with photonic bandgaps at micrometre and sub-micrometre wavelengths, and with rationally designed line and point defects for optical circuitry. Here we describe single crystals of silicon inverse opal with a complete three-dimensional photonic bandgap centred on 1.46 microm, produced by growing silicon inside the voids of an opal template of dose-packed silica spheres that are connected by small 'necks' formed during sintering, followed by removal of the silica template. The synthesis method is simple and inexpensive, yielding photonic crystals of pure silicon that are easily integrated with existing silicon-based microelectronics.     

Active control of slow light on a chip with photonic crystal waveguides

It is known that light can be slowed down in dispersive materials near resonances. Dramatic reduction of the light group velocity-and even bringing light pulses to a complete halt-has been demonstrated recently in various atomic and solid state systems, where the material absorption is cancelled via quantum optical coherent effects. Exploitation of slow light phenomena has potential for applications ranging from all-optical storage to all-optical switching. Existing schemes, however, are restricted to the narrow frequency range of the material resonance, which limits the operation frequency, maximum data rate and storage capacity. Moreover, the implementation of external lasers, low pressures and/or low temperatures prevents miniaturization and hinders practical applications. Here we experimentally demonstrate an over 300-fold reduction of the group velocity on a silicon chip via an ultra-compact photonic integrated circuit using low-loss silicon photonic crystal waveguides that can support an optical mode with a submicrometre cross-section. In addition, we show fast (approximately 100 ns) and efficient (2 mW electric power) active control of the group velocity by localized heating of the photonic crystal waveguide with an integrated micro-heater.     

一维非线性光子晶体全光开关

为得到响应时间较短的全光开关,在光子晶体的所有高折射率层掺入Kerr介质,基于Kerr非线性效应导致的禁带整体移动原理,设计了两种一维光子晶体全光开关结构。应用时域有限差分(FD-TD：Finite Difference-Time Domain)法,编制Matlab计算程序,对全光开关进行数值特性分析。讨论频率混合效应对全光开关的影响。观察光子局域效应增强光子晶体非线性的现象,验证光子局域效应与光子晶体完整周期结构的层数有关,层数太少光子局域效应不明显。     

Broad-band optical parametric gain on a silicon photonic chip

Developing an optical amplifier on silicon is essential for the success of silicon-on-insulator (SOI) photonic integrated circuits. Recently, optical gain with a 1-nm bandwidth was demonstrated using the Raman effect, which led to the demonstration of a Raman oscillator, lossless optical modulation and optically tunable slow light. A key strength of optical communications is the parallelism of information transfer and processing onto multiple wavelength channels. However, the relatively narrow Raman gain bandwidth only allows for amplification or generation of a single wavelength channel. If broad gain bandwidths were to be demonstrated on silicon, then an array of wavelength channels could be generated and processed, representing a critical advance for densely integrated photonic circuits. Here we demonstrate net on/off gain over a wavelength range of 28 nm through the optical process of phase-matched four-wave mixing in suitably designed SOI channel waveguides. We also demonstrate wavelength conversion in the range 1,511-1,591 nm with peak conversion efficiencies of +5.2 dB, which represents more than 20 times improvement on previous four-wave-mixing efficiencies in SOI waveguides. These advances allow for the implementation of dense wavelength division multiplexing in an all-silicon photonic integrated circuit. Additionally, all-optical delays, all-optical switches, optical signal regenerators and optical sources for quantum information technology, all demonstrated using four-wave mixing in silica fibres, can now be transferred to the SOI platform.     

金涂覆光子晶体光纤偏振滤波器的特性分析

设计了一种基于表面等离子体共振的光子晶体光纤偏振滤波器.在空气孔中选择性金涂覆使表面等离子体模式与纤芯模式共振.利用有限元法分析了改变结构参数对滤波器性能的影响.数值模拟结果表明金薄膜厚度和空气孔直径能够优化表面等离子体模式及纤芯模式的共振峰位置和强度，在波长1.31μm 处x偏振方向的损耗到达740.5dB/cm，y偏振方向的损耗很低且x，y方向的损耗峰明显地被分开.利用这些特性设计出一种新型的工作在通信波段的光子晶体光纤偏振滤波器.     

Trapping and emission of photons by a single defect in a photonic bandgap structure

By introducing artificial defects and/or light-emitters into photonic bandgap structures, it should be possible to manipulate photons. For example, it has been predicted that strong localization (or trapping) of photons should occur in structures with single defects, and that the propagation of photons should be controllable using arrays of defects. But there has been little experimental progress in this regard, with the exception of a laser based on a single-defect photonic crystal. Here we demonstrate photon trapping by a single defect that has been created artificially inside a two-dimensional photonic bandgap structure. Photons propagating through a linear waveguide are trapped by the defect, which then emits them to free space. We envisage that this phenomenon may be used in ultra-small optical devices whose function is to selectively drop (or add) photons with various energies from (or to) optical communication traffic. More generally, our work should facilitate the development of all-optical circuits incorporating photonic bandgap waveguides and resonators.     

表面等离子体共振型光子晶体光纤偏振滤波器性能优化设计方法

以一种常见的光子晶体光纤为载体,利用金属填充物和纤芯周围折射率环境结构的不对称性,提出了一种基于表面等离子体共振效应的光子晶体光纤偏振滤波器性能优化设计方法.研究发现,通过对光子晶体光纤纤芯和金属填充物周围结构的特殊设计,可有效调控周围材料的有效折射率,以实现金属等离子体模式的双折射效应和光纤纤芯模式的双折射特性.因此,当纤芯模式和金属的表面等离子体模式满足相位匹配条件时,即可达到偏振滤波的效果,并获得很好的消光比,而不需要对光子晶体光纤的结构进行复杂设计,降低了器件制备难度,避免了所设计的光纤结构无法实现实际制备的问题.     

On-chip natural assembly of silicon photonic bandgap crystals.

Photonic bandgap crystals can reflect light for any direction of propagation in specific wavelength ranges. This property, which can be used to confine, manipulate and guide photons, should allow the creation of all-optical integrated circuits. To achieve this goal, conventional semiconductor nanofabrication techniques have been adapted to make photonic crystals. A potentially simpler and cheaper approach for creating three-dimensional periodic structures is the natural assembly of colloidal microspheres. However, this approach yields irregular, polycrystalline photonic crystals that are difficult to incorporate into a device. More importantly, it leads to many structural defects that can destroy the photonic bandgap. Here we show that by assembling a thin layer of colloidal spheres on a silicon substrate, we can obtain planar, single-crystalline silicon photonic crystals that have defect densities sufficiently low that the bandgap survives. As expected from theory, we observe unity reflectance in two crystalline directions of our photonic crystals around a wavelength of 1.3 micrometres. We also show that additional fabrication steps, intentional doping and patterning, can be performed, so demonstrating the potential for specific device applications.     

2022年太赫兹人工表面等离激元科技热点回眸

随着第六代通信技术（6G）、空间态势感知等系统对高通量、高带宽要求的进一步提高,太赫兹技术成为国际学术界和工业界的研究热点。2022年,太赫兹人工表面等离激元研究在国际上受到很大的关注,盘点了该领域的关键热点与新进展,包括基于太赫兹人工表面等离激元的无源器件、有源器件、传感器、通信系统以及生物医药应用等。人工表面等离激元对传输的电磁波具有亚波长的电场束缚能力和非线性色散特性,为太赫兹功能器件和系统应用的实现带来了新机遇。     

基于光子晶体光纤非线性环路镜光开关的研究

采用光子晶体光纤构成非线性光学环路镜,利用非线性环路镜中信号光与控制光之间交叉相位调制效应实现全光开关. 讨论了光子晶体光纤结构参数对其非线性的影响,建立了基于光子晶体光纤非线性环路镜光开关的理论模型,研究了光开关的透过特性及影响光开关性能的因素. 研究结果表明,基于光子晶体光纤非线性环路镜的光开关,可以在较短的环长和较低的开关功率下实现高速光开关操作,其开关特性可由控制光功率灵活调控. 光子晶体光纤非线性环路镜光开关为实现用于高速光通信系统中的光开关技术提供了一种重要思路.     

不同材料逆古斯汉欣位移机理的对比研究

通过计算分界面附近的能流矢量曲线,对贵金属、超材料和负折射光子晶体表面的逆古斯汉欣位移的物理机制进行了研究.结果表明,虽然一定频率的入射光波在这3类材料表面反射时都能产生逆古斯汉欣位移,但逆古斯汉欣位移发生的物理机制完全不同.金属表面产生的逆古斯汉欣位移是因为TM偏振入射光诱导金属表面自由电子振荡,从而激发表面等离子体波;超材料表面产生的逆古斯汉欣位移是因为反射光束相对入射光束发生了相位突变;负折射光子晶体表面产生的逆古斯汉欣位移是光子晶体的等效负折射效应和周期性表面的综合作用,即全反射时激发了后向表面波.     

有源光电子器件技术及其发展

全光通信是光纤通信发展的必然方向，有源光电子器件是构建全光通信网络的重要基础。介绍了目前常用的几种有源光电子器件的现状及发展情况，并对其技术的未来发展趋势进行了分析和总结。     

多光楔板制作大面积光折变光子微结构

提出了一种制作大面积光子微结构的简便方法,利用多光楔板产生大面积的多光束干涉,在光折变晶体中制作出了大面积的周期性光子微结构和准周期性的光子准晶微结构。该方法简便易行,系统稳定性好,无须复杂的调节装置,制作效率高。使用导波强度图像、远场衍射图样、布里渊区光谱成像等方法对制作的大面积光子微结构进行了验证和分析。设计不同的多光楔板,可以制作出多种更复杂的大面积光子微结构。通过适当的处理,制作的大面积光子微结构可以长久地固定在光折变晶体中,也可以擦除后用于制作新的结构,这在集成光学和微纳光子器件领域具有良好的应用前景。     

All-optical signal processing for linearity enhancement of Mach–Zehnder modulators

This paper presents the fundamental principles and recent advances in the field of linearity enhancement of Mach–Zehnder modulators in microwave photonic systems using all-optical signal processing.A review of the fundamentals and applications that implement the linearity improvement is also provided.     

基于矩形谐振腔MIM波导结构的表面等离子体带阻滤波器

采用二维时域有限差分法(FDTD)设计并验证了一种新型的基于金属-介质-金属(metal-insulator-metal,MIM)多矩形谐振腔结构的表面等离子体带阻滤波器.该结构由一波导通道和一列平行排列于波导上方的矩形谐振腔组成.当矩形腔的长度对某一波长满足法布里-珀罗(F-P)谐振条件时,该波长的表面等离子体(Surface Plasmon Polaritons,SPPs)将进入腔内并发生耦合共振而被限制在其内,起到滤波的效果.通过调整谐振腔的长度和数量,可以方便地滤掉一个或多个不同波长的光波.与其他结构SPPs滤波器相比,此结构更具有简洁、滤过的波长更窄、更小的能量损耗等优点,该种滤波器可以应用于高集成电路等光学设备.     

集成光子器件封装形式对器件性能的影响

集成光子器件封装过程中,波导芯片与阵列光纤对准耦合完成之后,需用紫外光固化胶进行固接,从而实现光路的互连。针对1×4通道平面波导芯片与阵列光纤的固接,以粘接区域为研究对象,通过-40~80℃的温度循环,采用有限元法分析各种固接形式的应力集中点、应力双折射、耦合损耗的变化规律及其因素;最后通过比较各种固接形式的仿真结果,得出结论,从而指导实验。结果表明:在-40~80℃范围内,温度对粘接面的应力双折射和耦合损耗的影响很小;双盖板固接形式对器件性能的影响最小,斜8°固接形式的效果最差。     

光分组交换网络技术展望

综述了当前光网络向高速大容量、智能化和向分组交换转变的发展趋势。介绍了在光域上直接实现数据包的传送、路由、波长变换、存贮和转发的光分组交换技术的优点和目前能够实现光分组交换的几种解决方案 ,包括光突发交换、光标记交换和全光时分复用交换等。光分组交换的核心是光信号处理技术。由于当前缺乏光子存储器和光子集成芯片 ,该技术还处于探索阶段 ,有待光子学新概念和新器件的突破。因此 ,不失时机地开展对光分组交换技术的研究是实现创新与跨越发展的机遇和挑战     

Bose-Einstein condensation on a microelectronic chip

Although Bose-Einstein condensates of ultracold atoms have been experimentally realizable for several years, their formation and manipulation still impose considerable technical challenges. An all-optical technique that enables faster production of Bose-Einstein condensates was recently reported. Here we demonstrate that the formation of a condensate can be greatly simplified using a microscopic magnetic trap on a chip. We achieve Bose-Einstein condensation inside the single vapour cell of a magneto-optical trap in as little as 700 ms-more than a factor of ten faster than typical experiments, and a factor of three faster than the all-optical technique. A coherent matter wave is emitted normal to the chip surface when the trapped atoms are released into free fall; alternatively, we couple the condensate into an 'atomic conveyor belt', which is used to transport the condensed cloud non-destructively over a macroscopic distance parallel to the chip surface. The possibility of manipulating laser-like coherent matter waves with such an integrated atom-optical system holds promise for applications in interferometry, holography, microscopy, atom lithography and quantum information processing.