An advanced Ⅲ-Ⅴ-on-silicon photonic integration platform

In many application scenarios,silicon(Si)photonics favors the integration of Ⅲ-Ⅴ gain material onto Si substrate to real-ize the on-chip light source.In addition to the current popular integration approaches of Ⅲ-Ⅴ-on-Si wafer bonding or dir-ect heteroepitaxial growth,a newly emerged promising solution of epitaxial regrowth on bonded substrate has attracted a lot of interests.High-quality Ⅲ-Ⅴ material realization and successful laser demonstrations show its great potential to be a promising integration platform for low-cost,high-integration density and highly scalable active-passive photonic integra-tion on Si.This paper reviews recent research work on this regrowth on bonded template platform including template de-velopments,regrown material characterizations and laser demonstrations.The potential advantages,opportunities and challenges of this approach are discussed.

Photonic integrated technology for multi-wavelength laser emission

We summarized the design, fabrication challenges and important technologies for multi-wavelength laser transmitting photonic integration. Technologies discussed include multi-wavelength laser arrays, monolithic integration and modularizing coupling and packaging. Fabrication technique requirements have significantly declined with the rise of reconstruction-equivalent-chirp and second nanoimprint mask technologies. The monolithic integration problem between active and passive waveguides can be overcome with Butt-joint and InP array waveguide grating technologies. The dynamic characteristics of multi-factors will be simultaneously measured with multi-port analyzing modules. The performance of photonic integration chips is significantly improved with the autoecious factors compensation packaging technique.

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 integratedⅢ-Ⅴlaser 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.

Dynamics of InAs/GaAs quantum dot lasers epitaxially grown on Ge or Si substrate

Growing semiconductor laser sources on silicon is a crucial but challenging technology for developing photonic integrated circuits(PICs).InAs/GaAs quantum dot(Qdot)lasers have successfully circumvented the mismatch problem betweenⅢ–Ⅴmaterials and Ge or Si,and have demonstrated efficient laser emission.In this paper,we review dynamical characteristics of Qdot lasers epitaxially grown on Ge or Si,in comparison with those of Qdot lasers on native GaAs substrate.We discuss properties of linewidth broadening factor,laser noise and its sensitivity to optical feedback,intensity modulation,as well as mode locking operation.The investigation of these dynamical characteristics is beneficial for guiding the design of PICs in optical communications and optical computations.

Ⅲ–Ⅴ compound materials and lasers on silicon

Silicon-based photonic integration has attracted the interest of semiconductor scientists because it has high luminous efficiency and electron mobility.Breakthroughs have been made in silicon-based integrated lasers over the past few decades.Here we review three main methods of integration ofⅢ–Ⅴ materials on Si,namely direct growth,bonding,and selectivearea hetero-epitaxy.TheⅢ–Ⅴmaterials we introduced mainly include materials such as GaAs and InP.The lasers are mainly lasers of related communication bands.We also introduced the advantages and challenges of the three methods.

Highly integrated photonic crystal bandedge lasers monolithically grown on Si substrates

Monolithic integration of Ⅲ-Ⅴ lasers with small footprint, good coherence, and low power consumption based on a CMOS-compatible Si substrate have been known as an efficient route towards high-density optical interconnects in the photonic integrated circuits. However, the material dissimilarities between Si and Ⅲ-Ⅴ materials limit the performance of monolithic microlasers. Here, under the pumping condition of a continuous-wave 632.8 nm He–Ne gas laser at room temperature, we achieved an InAs/GaAs quantum dot photonic crystal bandedge laser, which is directly grown on an on-axis Si(001) substrate, which provides a feasible route towards a low-cost and large-scale integration method for light sources on the Si platform.

Photonic circuits written by femtosecond laser in glass:improved fabrication and recent progress in photonic devices

Integrated photonics is attracting considerable attention and has found many applications in both classical and quantum optics,fulfilling the requirements for the ever-growing complexity in modern optical experiments and big data communication.Femtosecond(fs)laser direct writing(FLDW)is an acknowledged technique for producing waveguides(WGs)in transparent glass that have been used to construct complex integrated photonic devices.FLDW possesses unique features,such as three-dimensional fabrication geometry,rapid prototyping,and single step fabrication,which are important for integrated communication devices and quantum photonic and astrophotonic technologies.To fully take advantage of FLDW,considerable efforts have been made to produce WGs over a large depth with low propagation loss,coupling loss,bend loss,and highly symmetrical mode field.We summarize the improved techniques as well as the mechanisms for writing high-performance WGs with controllable morphology of cross-section,highly symmetrical mode field,low loss,and high processing uniformity and efficiency,and discuss the recent progress of WGs in photonic integrated devices for communication,topological physics,quantum information processing,and astrophotonics.Prospective challenges and future research directions in this field are also pointed out.

Thermally reconfigurable quantum photonic circuits at telecom wavelength by femtosecond laser micromachining

The importance of integrated quantum photonics in the telecom band is based on the possibility of interfacing with the optical network infrastructure that was developed for classical communications.In this framework,femtosecond laser-written integrated photonic circuits,which have already been assessed for use in quantum information experiments in the 800-nm wavelength range,have great potential.In fact,these circuits,being written in glass,can be perfectly mode-matched at telecom wavelength to the in/out coupling fibers,which is a key requirement for a low-loss processing node in future quantum optical networks.In addition,for several applications,quantum photonic devices must be dynamically reconfigurable.Here,we experimentally demonstrate the high performance of femtosecond laser-written photonic circuits for use in quantum experiments in the telecom band,and we demonstrate the use of thermal shifters,which were also fabricated using the same femtosecond laser,to accurately tune such circuits.State-of-the-art manipulation of single-and two-photon states is demonstrated,with fringe visibilities greater than 95%.The results of this work open the way to the realization of reconfigurable quantum photonic circuits based on this technological platform.

集成互注入半导体激光器的微波光子学应用

光源是微波光子(microwave photonic,MWP)系统的“发动机”,从根本上决定了系统性能的上限。光注入半导体激光器集聚诸多优势,但离散器件引发的系统集成度低、结构复杂、体积大、稳定性差等弊端明显,大大限制了MWP系统的工程化应用。集成化是解决目前MWP技术实用化等瓶颈问题的关键,轻量级、高性能、多功能的激光器光源是集成MWP系统的关键。基于此,本文综述了近年来集成互注入半导体激光器在高效电光转换、微波信号产生、MWP变频、弱信号探测以及光学频率梳源等MWP应用方面的创新研究,期望为集成MWP系统提供可行的高性能集成光源,推动集成MWP技术的工程化应用尽快实现。

单光子激光通信测距一体化系统设计

超导单光子探测技术能够实现光子量级极微弱光接收,是深空探测的关键技术之一,然而光子概率分布产生的脉冲抖动效应造成通信、测距性能恶化。对此,设计了基于脉冲位置调制(pulse position modulation,PPM)调制的单光子激光通信测距一体化系统。根据光子分布特性,提出了脉冲宽度压缩的PPM新波形,降低了脉冲抖动效应对通信可靠性、测距精度的影响。同时,研制了星载端与地面端原理样机,搭建了双向通信与同步转发测距试验验证平台。试验验证结果表明,同等接收功率(-53.2 dBm)条件下,采用1/4脉宽压缩比时,通信接收误码率从4.7×10^(-4)降至5×10^(-10),测距精度从23.61 cm提高至0.91 cm,实现了高可靠通信传输与高精度距离测量。

Advances of semiconductor mode-locked laser for optical frequency comb generation

Semiconductor mode-locked lasers(MLLs)can provide coherent optical frequency combs(OFCs)with high repetition rates and output power,which have been recognized as potential multi-wavelength sources used in optical communication field due to their compactness,high-efficiency,and low-cost properties.In this article,we have reviewed recent development of semiconductor MLL-based frequency comb generation.Different approaches of semiconductor MLLs for OFC generation are synoptically summarized based on various material platforms.The representative progress of III-V semiconductor MLLs on III-V platform and especially on Si substrates is both discussed for the applications in integrated silicon photonics.

Compact packaging for multi-wavelength DML TOSA

A compact multi-wavelength hybrid-integrated directly-modulated distributed-feedback laser(DML)transmitter optical sub-assembly(TOSA)has been achieved in our laboratory.The 8-channel distributed feedback(DFB)lasers are monolithically integrated based on the reconstruction-equivalent-chirp(REC)technology.With the high-density and high-speed packaging technique,the laser array and a multi-mode interference(MMI)multiplexer are assembled in the TOSA.The channel spacing of the TOSA is 200 GHz between adjacent lasers.It meets the 8 9 12.5 Gb/s operation demand and gives rather low channel crosstalk of less than-25 dB.This compact TOSA is of effective cost and shows good stability for mass production,which is expected to improve the performance of devices in access networks,data centers and supercomputing.

Heterogeneous 2D/3D photonic integrated microsystems

The continuing trend of exponential growth in data communications and processing are driving the need for large-scale heterogeneous integration.Similar to the trend we have observed in electronic integrated circuit development,we are witnessing a growing trend in 3D photonic integrated circuits(PICs)development in addition to that in 2D PICs.There are two main methods for fabricating 3D PICs.The first method,which utilizes ultrafast laser inscription(ULI),offers freeform shaping of waveguides in arbitrary contours and formations.The second method,which utilizes multilayer stacking and coupling of planar PICs,exploits relatively mature 2D PIC fabrication processes applied to each layer sequentially.Both the fabrication methods for 3D PICs have advantages and disadvantages such that certain applications may favor one method over the other.However,a joining of 2D PICs with 3D PICs can help develop integrated microsystems with new functionalities such as non-mechanical beam steering,spacedivision multiplexing(SDM),programmable arbitrary beam shaping,and photonic signal processing.We discuss examples of 3D PICs and 2D/3D integrated PICs in two applications:SDM via orbital-angular-momentum(OAM)multiplexing/demultiplexing and optical beam steering using optical phased arrays.Although a 2D PIC by itself can function as an OAM multiplexer or demultiplexer,it has limitations in supporting both polarizations.Alternatively,a 3D PIC fabricated by ULI can easily support both polarizations with low propagation loss.A combination of a 3D PIC and a 2D PIC designed and fabricated for OAM applications has successfully multiplexed and demultiplexed 15 OAM states to demonstrate polarization-diversified SDM coherent optical communications using multiple OAM states.Coherent excitation of multi-ring OAM states can allow highly scalable SDM utilizing Laguerre–Gaussian modes or linearly polarized(LP)modes.The preliminary fabrication of multi-ring OAM multiplexers and demultiplexers using the multilayer 3D PIC method and the ULI 3D PIC method has also been pursued.Large-scale(for example,16×16 optical phased array)3D PICs fabricated with the ULI technique have been demonstrated.Through these examples,we show that heterogeneous 2D/3D photonic integration retains the advantages of 2D PICs and 3D waveguides,which can potentially benefit many other applications.

基于光注入半导体激光器的雷达通信一体化研究

雷达通信一体化是近年来研究的热点之一,它能够在单一系统中同时实现目标探测和数据传输两种功能.本文提出了一种结构简单紧凑的基于光注入半导体激光器的雷达通信一体化方案.利用注入相位调制光信号的N阶调制光边带锁定从激光器,以提高主从激光器之间的相干性;通过改变从激光器单周期振荡频率和注入光信号,可以实现工作频段和倍频因子均可调谐的幅度键控线性调频(Amplitude Shift-Keying Linearly Frequency-Modulated,ASK-LFM)信号的生成,并通过实验和仿真验证了基于该信号的一体化系统的雷达与通信功能.实验结果表明,对于带宽为1 GHz的ASK-LFM信号,目标距离测量误差优于3.2 cm,3个探测目标成像结果可分辨且能够同时实现通信数据的正确传输.

硅基量子点激光器研究进展

随着全球数据流量的不断增长,硅基光子集成电路已经成为高性能芯片内/芯片间光通信领域中一个极具发展潜力的研究方向。然而,由于本征硅的发光效率极低,硅基片上光源成为光子集成电路中最具挑战性的元器件。为了解决缺乏原生光源的问题,硅基集成的Ⅲ-Ⅴ族半导体激光器已经得到了广泛研究,该激光器提供了优越的光学和电学性能。值得注意的是,在Ⅲ-Ⅴ族半导体激光器中使用量子点作为增益介质已经引起了诸多关注,因为它具有多种优点,如对晶体缺陷的容忍度高、温度敏感度低、阈值电流密度低和反射灵敏度低等。使用量子点的激光增益区在光子集成方面相比量子阱有许多改进。增益带宽可以根据需要进行设计优化,并在整个近红外光范围内实现激射。量子态与周围材料的大能级分离使其获得了优异的高温性能和亚皮秒时间尺度的增益恢复。本文从量子点材料及量子点激光器、基于晶圆键合技术、基于倒装键合技术、基于直接外延生长技术等多个角度,综述了硅基Ⅲ-Ⅴ族半导体量子点激光器的最新研究进展,并对其未来前景和挑战进行了探讨。

硅基Ⅲ-Ⅴ族量子点激光器的发展现状和前景

本文简要综述了硅基Ⅲ-Ⅴ族量子点激光器的研究进展.在介绍了量子点激光器的优势和发展后,重点介绍了近年来硅基、锗基Ⅲ-Ⅴ族量子点材料生长上的突破性进展及所带来的器件性能的大幅提高,如实现了锗基和硅基1.3μm InAs/GaAs量子点激光器的室温激射,锗基量子点激光器的阈值电流低至55.2 A/cm^2并可达60℃以上的连续激射,通过锗硅虚拟衬底,在硅基上实现了30℃下以16.6 mW的输出功率达到4600 h的激光寿命,这些突破性的进展为硅基光电子集成打开了新的大门.

异质集成微波光子器件发展现状

微波光子学利用光子技术实现微波信号的产生、传输、处理及控制,可突破传统微波技术在带宽、传输损耗和抗电磁干扰等方面的瓶颈,提升雷达、电子战等信息系统的综合性能。激光器、电光调制器和光电探测器是微波光子技术中的三种核心光电子器件,其性能对微波光子链路的噪声和动态等指标具有决定性的影响,但基于分立器件的微波光子系统体积、重量较大,难以满足雷达、电子战等系统的阵列化需求,硅基异质集成技术以及高密度低损耗片上光传输互连技术是解决有源器件集成和无源器件集成的关键技术。文章介绍了用于微波光子的硅基激光器、电光调制器、光电探测器和波导的异质集成技术的发展现状,并探讨了集成微波光子技术的发展趋势。

微波光子与多学科交叉融合的前景展望(特邀)

微波光子学可借助光电子器件实现微波信号的产生、处理、接收和分配等功能,具有宽带、低传输损耗、轻重量、快速可重构及抗电磁干扰等优势。随着微波光子学的理论方法和技术应用的不断发展,微波光子与多学科交叉融合成为其核心发展方向。文中对微波光子与部分学科交叉融合的现状进行了总结,并对微波光子与激光技术、集成光电子学、量子技术和人工智能等前沿学科的交叉融合进行了展望。

Latest advances in high-performance light sources and optical amplifiers on silicon

Efficient light generation and amplification has long been missing on the silicon platform due to its well-known indirect bandgap nature.Driven by the size,weight,power and cost(SWaP-C)requirements,the desire to fully realize integrated silicon electronic and photonic integrated circuits has greatly pushed the effort of realizing high performance on-chip lasers and amplifiers moving forward.Several approaches have been proposed and demonstrated to address this issue.In this paper,a brief overview of recent progress of the high-performance lasers and amplifiers on Si based on different technology is presented.Representative device demonstrations,including ultra-narrow linewidthⅢ-Ⅴ/Si lasers,fully integratedⅢ-Ⅴ/Si/Si3N4 lasers,high-channel count mode locked quantum dot(QD)lasers,and high gain QD amplifiers will be covered.

Highlighting photonics: looking into the next decade

Let there be light-to change the world we want to be!Over the past several decades,and ever since the birth of the first laser,mankind has witnessed the development of the science of light,as light-based technologies have revolutionarily changed our lives.Needless to say,photonics has now penetrated into many aspects of science and technology,turning into an important and dynamically changing field of increasing interdisciplinary interest.In this inaugural issue of eLight,we highlight a few emerging trends in photonics that we think are likely to have major impact at least in the upcoming decade,spanning from integrated quantum photonics and quantum computing,through topological/non-Hermitian photonics and topological insulator lasers,to AI-empowered nanophotonics and photonic machine learning.This Perspective is by no means an attempt to summarize all the latest advances in photonics,yet we wish our subjective vision could fuel inspiration and foster excitement in scientific research especially for young researchers who love the science of light.