Wide Bandgap Phase Change Material Tuned Visible Photonics

Light strongly interacts with structures that are of a similar scale to its wavelength, typically nanoscale features for light in the visible spectrum. However, the optical response of these nanostructures is usually fixed during the fabrication. Phase change materials offer a way to tune the properties of these structures in nanoseconds. Until now, phase change active photonics has used materials that strongly absorb visible light, which limits their application in the visible spectrum. In contrast, Sb₂S₃ is an underexplored phase change material with a bandgap that can be tuned in the visible spectrum from 2.0 to 1.7 eV. This tuneable bandgap is deliberately coupled to an optical resonator such that it responds dramatically in the visible spectrum to Sb₂S₃ reversible structural phase transitions. It is shown that this optical response can be triggered both optically and electrically. High‐speed reprogrammable Sb₂S₃ based photonic devices, such as those reported here, are likely to have wide applications in future intelligent photonic systems, holographic displays, and microspectrometers.     

硅光子学

硅光子学有六个主要研究领域,包括产生光、在硅中选择地引导和传输光、编码光、探测光、包装器件和智能地控制这一切光子功能。综述了以上各领域的研究进展。     

面向中红外应用的硅基光电子学最近研究进展

随着信息传递、处理以及存储能力要求的不断提升,传统的近红外通信波段已呈“容量紧缩”之势。而工艺与CMOS兼容、结构简单、成本低廉的硅基光电子技术在中红外信号传输和处理方面已经显示出独特优势,有望在中红外波段实现大规模集成,在非线性光学等领域实现新的飞跃。首先介绍了硅基光电子技术在中红外应用中的优势以及目前研究过程中所遇到的困难和挑战;其次结合材料属性和结构特性对一些基本元件（如波导、分束/合束器、二极管）等在中红外领域的最新研究成果进行了介绍;最后对近5年来在中红外波段所实现传感应用的非线性光学硅基器件（基于FWM的非线性光学器件、频率梳）和面向中红外通信应用的激光器、调制器、光电探测器进行了成果介绍,并对研究进展进行了总结。     

Non-Volatile Optical Switch Element Enabled by Low-Loss Phase Change Material

Mach–Zehnder interferometers (MZIs) integrated with phase-change materials have attracted great interest due to their low power consumption and ultra-compact size, which are favored for reconfigurable photonic processors. However, they suffer from a low optical extinction ratio and limited switching cycles due to high material loss and poor reversible repeatability caused by material degradation. Here a non-volatile electrically reconfigurable 2 × 2 MZI integrated with a low-loss phase-change material Sb₂Se₃ encapsulated in Al₂O₃ layers is demonstrated. The phase change is electrically actuated by a forward-biased silicon p-i-n diode. The switch extinction ratio is more than 20 dB due to the low-loss Sb₂Se₃-based phase shifter. By dividing the Sb₂Se₃ patch into small sub-cells to restrict the material reflow, more than 10 000 reversible phase-change cycles and 6-bit multilevel switching states are achieved by programming the electrical pulses. Its non-volatility, high endurance, and fine-tuning capability makes the device promising in large-scale low-power reconfigurable photonic processors.     

硅光子中波分复用技术研究

介绍了硅光子互连中4种波分复用器及相关单片集成发射接收芯片,其中硅纳米线阵列波导光栅及刻蚀衍射光栅波分复用器单个芯片就可以成倍扩展通道数,非常适合大通道数密集波分复用,马赫-曾德尔结构及微环谐振型波分复用器芯片通道数增大时需要多个单元级联,波长准确性及间隔不易控制,比较适合通道数少的芯片应用。同时,给出了自主设计和制备的硅纳米线阵列波导光栅和刻蚀衍射光栅,通过采用阵列波导展宽方法,有效抑制了阵列波导的串扰,实现串扰小于-15 d B;通过在刻蚀衍射光栅反射面引入二维光子晶体反射镜,降低了刻蚀衍射光栅的反射损耗,损耗比普通刻蚀衍射光栅减小了3 d B。     

太赫兹与硅光子技术融合应用展望

本文讨论了硅光子技术的发展现状,尤其对于其中进行光电,电光转换的主要模块的性能指标进行了介绍, 详细 阐述了全芯片集成的硅光子技术的优缺点, 对其在光控相控阵雷达领域的潜在应用进行了探讨。提出了将硅光子技术应 用于太赫兹雷达系统的初步设想。     

Orientation‐Controlled Selective‐Area Epitaxy of III–V Nanowires on (001) Silicon for Silicon Photonics

Monolithic integration of III–V nanowires on silicon platforms has been regarded as a promising building block for many on‐chip optoelectronic, nanophotonic, and electronic applications. Although great advances have been made from fundamental material engineering to realizing functional devices, one of the remaining challenges for on‐chip applications is that the growth direction of nanowires on Si(001) substrates is difficult to control. Here, catalyst‐free selective‐area epitaxy of nanowires on (001)‐oriented silicon‐on‐insulator (SOI) substrates with the nanowires aligned to desired directions is proposed and demonstrated. This is enabled by exposing {111} planes on (001) substrates using wet chemical etching, followed by growing nanowires on the exposed planes. The formation of nanowire array‐based bottom‐up photonic crystal cavities on SOI(001) and their coupling to silicon waveguides and grating couplers, which support the feasibility for on‐chip photonic applications are demonstrated. The proposed method of integrating position‐ and orientation‐controllable nanowires on Si(001) provides a new degree of freedom in combining functional and ultracompact III–V devices with mature silicon platforms.     

旋转载体用硅微机械陀螺的相位研究

介绍了利用旋转载体自身旋转作为驱动力的硅微机械陀螺的相位提取技术。当陀螺的敏感轴平行于载体偏转平面时，硅摆所受的哥氏力最大，输出为正弦信号的峰值；当它的敏感轴和偏转平面垂直时，输出为正弦信号的零值。因此，以载体的自转信号为基准，通过比较输出信号波峰在输入基准坐标中相位的变化可知敏感轴的方向，进而能够确定旋转平面及载体在空间中的偏转方向。     

旋转载体用硅微机械陀螺的相位研究

介绍了利用旋转载体自身旋转作为驱动力的硅微机械陀螺的相位提取技术。当陀螺的敏感轴平行于载体偏转平面时,硅摆所受的哥氏力最大,输出为正弦信号的峰值;当它的敏感轴和偏转平面垂直时,输出为正弦信号的零值。因此,以载体的自转信号为基准,通过比较输出信号波峰在输入基准坐标中相位的变化可知敏感轴的方向,进而能够确定旋转平面及载体在空间中的偏转方向。     

硅基波导用楔形模斑变换器的研究进展

楔形模斑变换器在利用硅基光子集成技术实现芯片间光互连中有着广泛的应用.文章概述了国内外楔形模斑变换器的最新研究进展.介绍了几种新型模斑变换器的结构及制作的工艺流程,并对其性能及影响楔形模斑变换器耦合效率的几个因素进行了分析比较,进而讨论了这几种模斑变换器存在的问题及进一步提高耦合效率的可能性.     

硅基微波光子波束形成器研究进展

微波波束形成器是相控阵雷达、5G通信基站等射频发射系统中的核心器件。近年来硅基微波光子波束形成器以其带宽大、尺寸紧凑、重量轻、损耗低、抗电磁干扰等优势成为微波光子学中的研究热点之一。文章从微波光子波束形成的基本原理和性能指标出发,总结了近年来应用于微波光子波束形成器的多种集成可调光学真延迟线结构和波束形成网络架构,并介绍了微波光子波束形成系统集成芯片和自动化控制的最新进展,最后对硅基微波光子波束形成器的未来发展进行了展望。     

多孔硅可见光发射研究

用常规电化学方法制备了发射高效可见光的多孔硅样品。对样品进行了光谱研究。用非化学方法从样品表面得到了粉末状荧光物质(非多孔硅膜研磨产物),光谱测定证实它的光致发光光谱与原多孔硅样品光致发光光谱相同,粉末进一步研磨后仍能发出同样的可见光。多孔硅样品还可以实现阴极射线激发发出同样的高效可见光,但易因电子束的轰击而发光强度较快减弱。用扫描电镜(SEM)对多孔硅样品的形貌、结构、荧光粉末的形状、尺寸、多孔硅样品阴极荧光发射区域进行了系统的研究。实验结果表明多孔硅样品一般可分为三层结构:表面层、多孔层和单晶硅衬底,样品荧光是来源于其表面层的。对样品表层组分的x射线光电子谱(XPS)分析表明,此时的多孔硅表层有大量非硅元素存在,如:C、O、F(没考虑H),硅元素的原子个数比只占30％～50％。用同样的电化学方法在单晶硅未抛光面上和多晶硅未抛光面上制得了均匀发射可见光样品。上述实验结果说明,多孔硅的高效可见光发射是来源于样品制备过程中在其表面层中形成的粉末状荧光物质。     

制备可见光致发光硅量子阱的激光晶化技术

我们利用Ａｒ＋激光辐照ａ－Ｓｉ：Ｈ／ａ－ＳｉＮｘ：Ｈ多量子阱结构材料，使ａ－Ｓｉ：Ｈ阱层晶化。在该样品中成功地观察到室温可见光致发光现象，研究了阱层厚度和激光辐照功率对光致发光峰峰位及半高宽的影响。     

Recent advances of heterogeneously integrated III–V laser on Si

Due to the indirect bandgap nature, the widely used silicon CMOS is very inefficient at light emitting. The integration of silicon lasers is deemed as the ‘Mount Everest’ for the full take-up of Si photonics. The major challenge has been the materials dissimilarity caused impaired device performance. We present a brief overview of the recent advances of integrated III–V laser on Si. We will then focus on the heterogeneous direct/adhesive bonding enabling methods and associated light coupling structures. A selected review of recent representative novel heterogeneously integrated Si lasers for emerging applications like spectroscopy, sensing, metrology and microwave photonics will be presented, including DFB laser array, ultra-dense comb lasers and nanolasers. Finally, the challenges and opportunities of heterogeneous integration approach are discussed.     

Perspective:optically-pumped Ⅲ–Ⅴ quantum dot microcavity lasers via CMOS compatible patterned Si (001) substrates

Direct epitaxial growthⅢ–Ⅴquantum dot(QD)structures on CMOS-compatible silicon substrates is considered as one of the most promising approaches to achieve low-cost and high-yield Si-based lasers for silicon photonic integration.However,epitaxial growth ofⅢ–Ⅴmaterials on Si encounters the following three major challenges:high density of threading dislocations,antiphase boundaries and thermal cracks,which significantly degrade the crystal quality and potential device performance.In this review,we will focus on some recent results related to InAs/GaAs quantum dot lasers on Si(001)substrates byⅢ–Ⅴ/Ⅳhybrid epitaxial growth via(111)-faceted Si hollow structures.Moreover,by using the step-graded epitaxial growth process the emission wavelength of InAs QDs can be extended from O-band to C/L-band.High-performance InAs/GaAs QD microdisk lasers with sub-milliwatts threshold on Si(001)substrates are fabricated and characterized.The above results pave a promising path towards the on-chip lasers for optical interconnect applications.     

Perspective: optically-pumped III–V quantum dot microcavity lasers via CMOS compatible patterned Si (001) substrates

Direct epitaxial growth III–V quantum dot (QD) structures on CMOS-compatible silicon substrates is considered as one of the most promising approaches to achieve low-cost and high-yield Si-based lasers for silicon photonic integration. However, epitaxial growth of III–V materials on Si encounters the following three major challenges: high density of threading dislocations, antiphase boundaries and thermal cracks, which significantly degrade the crystal quality and potential device performance. In this review, we will focus on some recent results related to InAs/GaAs quantum dot lasers on Si (001) substrates by III–V/IV hybrid epitaxial growth via (111)-faceted Si hollow structures. Moreover, by using the step-graded epitaxial growth process the emission wavelength of InAs QDs can be extended from O-band to C/L-band. High-performance InAs/GaAs QD micro-disk lasers with sub-milliwatts threshold on Si (001) substrates are fabricated and characterized. The above results pave a promising path towards the on-chip lasers for optical interconnect applications.     

硅基单片集成单边带调制器

基于CMOS兼容的硅基光子集成工艺,设计并实现了一种具有高边带抑制比的硅基单片集成单边带调制器。单边带调制器采用正交混合耦合器实现上下两臂等幅度、90°相位差的射频信号加载,基于硅基双驱动马赫曾德尔调制器的热移相器调控上下两臂光相位差为90°,实现了效果显著的单边带抑制。基于CUMEC公司CSiP180 Al工艺和工艺设计包(PDK)完成芯片制备,采用金丝引线实现了正交混合耦合器的空气桥结构。测试结果显示该硅基单片集成单边带调制器在18~32 GHz频率内边带抑制比均高于12 dB,在21 GHz工作频率时边带抑制比达到了32 dB。该单边带调制器有望应用在光通信和微波光子系统中。     

低电压驱动的硅基Ka波段级联式MEMS移相器

通过在共平面波导上周期性地分布微机械电容,外加电压驱动改变电容值,可实现级联式MEMS移相器.本文讨论了优化相移特性对共平面波导特性阻抗及下拉电压的要求,通过工艺参数优化制备了高阻硅基上的Ka波段级联式MEMS移相器,测试结果表明制备器件具有较低的驱动电压,8V时即产生明显的相移量,在36GHz处15V驱动电压时相移量为118°,25V时为286°.对微结构弹性膜的机械振动寿命测试表明,13级级联的MEMS移相器所有弹性膜同步振动的寿命为3×10⁶次.为器件的实用化提供了重要保障.     

A New Family of Ultralow Loss Reversible Phase‐Change Materials for Photonic Integrated Circuits: Sb2S3 and Sb2Se3

Phase‐change materials (PCMs) are seeing tremendous interest for their use in reconfigurable photonic devices; however, the most common PCMs exhibit a large absorption loss in one or both states. Here, Sb₂S₃ and Sb₂Se₃ are demonstrated as a class of low loss, reversible alternatives to the standard commercially available chalcogenide PCMs. A contrast of refractive index of Δn = 0.60 for Sb₂S₃ and Δn = 0.77 for Sb₂Se₃ is reported, while maintaining very low losses (k < 10^?5) in the telecommunications C‐band at 1550 nm. With a stronger absorption in the visible spectrum, Sb₂Se₃ allows for reversible optical switching using conventional visible wavelength lasers. Here, a stable switching endurance of better than 4000 cycles is demonstrated. To deal with the essentially zero intrinsic absorption losses, a new figure of merit (FOM) is introduced taking into account the measured waveguide losses when integrating these materials onto a standard silicon photonics platform. The FOM of 29 rad phase shift per dB of loss for Sb₂Se₃ outperforms Ge₂Sb₂Te₅ by two orders of magnitude and paves the way for on‐chip programmable phase control. These truly low‐loss switchable materials open up new directions in programmable integrated photonic circuits, switchable metasurfaces, and nanophotonic devices.