铌酸锂薄膜微腔激光器研究进展（特邀）

绝缘体上铌酸锂薄膜凭借铌酸锂晶体优异的光学性能和薄膜器件的易加工和可集成特性,被视为理想的集成光学平台。除了波导、调制器等传输、控制器件方面的研究之外,最近铌酸锂薄膜激光器的研究也取得了显著的进展。文中将对最近迅速发展的铌酸锂薄膜微腔激光器的研究现状进行综述。首先,介绍铌酸锂晶体和铌酸锂薄膜稀土离子掺杂的主要技术方案,以及近期有关于稀土离子掺杂铌酸锂薄膜微纳光学器件制备方面的探索;其次,总结近年来掺铒铌酸锂薄膜微盘腔、微环腔激光器方面的研究进展;然后,阐述微腔激光器体系几种常见的实现单模激光器方法的工作机理,介绍研究者们利用“游标效应”调制模式损耗等方式实现掺铒铌酸锂薄膜单模激光器的研究进展;最后,基于目前报导的铌酸锂薄膜激光器研究成果,对目前研究存在的局限性以及未来的研究方向进行了探讨。     

基于电感耦合等离子体刻蚀的LNOI脊形微结构制备

铌酸锂(LiNbO₃,LN)是一种广泛使用的介电材料,由于其电光系数大,透明范围大,本征带宽宽,因而在集成和非线性光学器件中极为重要。但绝缘体上铌酸锂薄膜(LNOI)的化学稳定性好,刻蚀速率慢,其微结构参数难以控制。针对以上问题,该文开展了基于电感耦合等离子体刻蚀(ICP-RIE)的LNOI脊形微结构的制备工艺研究,分析了腔室压强、气体总流量及刻蚀功率等参数对刻蚀速率、刻蚀倾角和表面粗糙度(RMS)的影响。研究表明,在优化的工艺条件下,LNOI薄膜的刻蚀速率达到24.9 nm/min,制备出刻蚀深度249 nm、刻蚀倾角76°、表面粗糙度(RMS)0.716 nm的LNOI脊形微结构。该文通过对刻蚀工艺与微观结构参数的研究,建立了基于ICP的LNOI微结构刻蚀方法,为控制LNOI脊形光波导和提升性能提供了工艺支撑。     

集成铌酸锂光子器件技术的研究进展

铌酸锂单晶薄膜(LNOI)具有透光光谱宽,折射率高,二阶非线性高及压电响应大等优点,是一种重要的集成光子学基础材料。LNOI材料具有亚波长尺度的光约束和光电器件的高密度集成能力,能够实现具有更高性能、更低成本的全新器件及应用,给光通信和微波光子学带来革命性的变革。该文重点综述了LNOI的制备技术、LNOI电光调制器、LNOI声光调制器和LNOI电光频率梳的最新研究进展,简要讨论了铌酸锂光子器件在制作工艺和系统实现中面临的挑战。     

1064nm低电压薄膜铌酸锂电光调制器

低半波电压电光调制器是实现大规模光电集成的关键。文章提出了一种半波电压低于1.5 V的薄膜铌酸锂马赫-曾德尔(Mach-Zehnder, MZ)电光调制器，选用绝缘体上单晶薄膜铌酸锂材料作为设计基础，分析了直波导、多模干涉耦合器、弯曲波导和调制臂等结构对电光调制器的影响。结果表明，当调制臂长为3 mm时，该薄膜铌酸锂电光调制器具有1.05 V的低半波电压、0.319 dB的低损耗和27 dB的高消光比。同时，该调制器半波电压长度积为0.315 V·cm,调制效率高，具有与CMOS技术兼容的半波电压，有利于大规模光电集成。     

全封装的薄膜铌酸锂电光调制器（特邀）

高速电光调制器是宽带光通信网络和微波光子系统中的关键元器件之一。相对于体材料铌酸锂而言,薄膜铌酸锂材料由于其较强的光场限制能力,在构建小尺寸、宽带、低半波电压的高性能电光调制芯片上有独特的优势。文章基于薄膜铌酸锂材料研制了一种3 dB带宽不低于50 GHz的电光调制芯片,并采用光纤与波导水平端面耦合的光学封装方案和基于1.85 mm同轴接头的射频封装方案,实现了全封装的薄膜铌酸锂电光调制器。测量结果表明,封装后器件的光学插入损耗小于等于5 dB,3 dB带宽大于等于40 GHz,射频半波电压小于等于3 V@1 GHz。     

高性能硅和铌酸锂异质集成薄膜电光调制器 （特邀）

硅基光子集成平台因其高集成度、CMOS工艺兼容性等特点在光通信领域受到了广泛的关注，而电光调制器作为光通信系统中最为重要的器件之一，承担着将电信号加载至光信号上的关键作用，为打破硅基调制器的性能限制，可利用硅和铌酸锂的大面积键合技术以及铌酸锂低损耗波导刻蚀技术实现高性能硅和铌酸锂异质集成薄膜电光调制器，目前该类调制器的性能可达半波电压3 V，3 dB电光带宽超过70 GHz，插入损耗小于1.8 dB, 消光比大于40 dB。文中对比了硅和铌酸锂异质集成调制器的研究现状并介绍了该异质集成薄膜调制器的结构设计与工艺实现方法。     

铌酸锂低半波电压电光调制器研究

对降低铌酸锂(LN)电光调制器的半波电压进行了研究,探索了利用反射结构实现低半波电压的原理.通过退火质子交换工艺在x切LN晶片上制作了反射结构的LN电光调制器.测试表明,这种反射结构的LN电光调制器在保持器件长度不变的条件下可以降低半波电压.     

Preface to the Special Issue on Semiconductor Optoelectronic Integrated Circuits

The family of perovskite materials derived from the crystal structure of the mineral CaTiO3,which was first reported in 1839[1].Then a series of materials with perovskite structure were discovered.Most perovskite materials have the ABX3 stoichiometry,in which A is monovalent or divalent cation,B is divalent or tetravalent cation,and X is monovalent or divalent anion.Perovskite materials play important roles in various functional devices due to their unique optical,electronic and optoelectronic properties.Inorganic perovskites such as BaTiO3 and PbTiO3 have been widely used in ferroelectric and piezoelectric devices,actuators,capacitors,and nonlinear optical devices[2].The emergence of organic–inorganic hybrid perovskites such as CH3NH3PbI3 triggers a new wave of research about perovskite-based devices,such as solar cells,light-emitting diodes(LEDs),photodetectors,lasers,and field-effect transistors[3,4].Motivated by the outstanding performance of perovskite materials,a variety of perovskite derivatives were developed,such as two-dimensional perovskites,double perovskites,and vacancy-ordered perovskites[5,6].     

交叉耦合效应对M-Z调制器谐波抑制比的影响

针对微波光子链路低噪声高线性度的应用需求,研究了Mach-Zehnder (M-Z)型电光调制器波导交叉耦合效应对谐波抑制比的影响。首先通过OptiBPM和MATLAB联合仿真发现波导间交叉耦合效应会导致调制器射频电极与偏置电极工作点的偏移,进而降低谐波抑制比;其次利用特制的窄波导间距铌酸锂调制器实测验证了该现象,最后提出了一种能快速检测M-Z型电光调制器交叉耦合效应的方法。文章不仅探索了波导结构对谐波抑制比的影响,还为用于微波光子技术的脊波导及光子晶体薄膜铌酸锂调制器的研制提供了一定参考。     

压电MEMS兰姆波器件技术的最新进展与展望

兰姆波谐振器(LWR)作为一种新兴的压电微机电系统(MEMS)声学器件,同时具有高工作频率、高机电耦合系数、高品质因数值及低功耗等特点,其制造工艺与集成电路工艺兼容,可在单片晶圆上实现多频率器件。基于LWR的声学滤波器是实现高性能射频前端组件的有效解决方案之一,能够满足未来通信设备多频率及集成化的发展要求,其相关研究已成为微声器件领域的热点。该文简要介绍了兰姆波的基本原理,综述了近年来基于氮化铝(AlN)薄膜和铌酸锂薄膜(LNOI)的压电MEMS兰姆波器件研究取得的最新成果,并讨论了压电MEMS兰姆波器件的发展趋势。     

电光晶体用于快速变焦的设计

在利用晶体的电光效应实现快速变焦时,需要合理地设计电光晶体及电极结构。基于晶体电光效应的基本原理,提出了其设计的基本原则和思路,并通过对一次电光晶体(铌酸锂晶体)和二次电光晶体(钽铌酸钾晶体)内部非均匀电场及其总附加光程的模拟和比较,获得了优化的电光晶体及电极设计结果。在此基础上,开展了电光晶体用于快速变焦设计的性能分析,并讨论了电光晶体长度、外加电压等参数对总附加光程的影响。结果表明:电光晶体的附加光程调制的曲率半径随控制电压增大而减小,在加载电压不变的情况下随晶体厚度的增大而增大。因此,在实际应用中,需要对晶体厚度和加载电压综合进行考虑,以获得最佳的变焦效果。     

Recent progress in integrated electro-optic frequency comb generation

Optical frequency combs have emerged as an important tool enabling diverse applications from test-and-measurement,including spectroscopy,metrology,precision distance measurement,sensing,as well as optical and microwave waveform synthesis,signal processing,and communications.Several techniques exist to generate optical frequency combs,such as mode-locked lasers,Kerr micro-resonators,and electro-optic modulation.Important characteristics of optical frequency combs include the number of comb lines,their spacing,spectral shape and/or flatness,and intensity noise.While mode-locked lasers and Kerr micro-resonators can be used to obtain a large number of comb lines compared to electro-optic modulation,the latter provides increased flexibility in tuning the comb spacing.For some applications in optical communications and microwave photonics,a high degree of integration may be more desirable over a very large number of comb lines.In this paper,we review recent progress on integrated electro-optic frequency comb generators,including those based on indium phosphide,lithium niobate,and silicon photonics.     

Lithium niobate electro-optic tunable filter with high sidelobe suppression

The first demonstration of a high sidelobe suppression, tunable, electro-optic filter fabricated in lithium niobate for 1.55 mu m is reported. Weighting of the mode convertor structure using a Taylor distribution resulted in a -3 dB passband width of 1.6 nm and nearest sidelobes of -25 dB. A continuous, linear electro-optic tuning rate of +or-30 V/nm is also reported.<>     

基于铌酸锂晶体电光效应的差频转换效率调制

为了在差频过程中得到较高的转换效率,利用铌酸锂晶体的电光效应来改变晶体的折射率,进而在非线性过程中调整位相失配量来实现差频转换效率的调制,模拟了外加电场对差频转换效率的影响。结果表明,利用铌酸锂晶体的电光效应,可以在任意给定抽运光强的情况下,获得较高的差频转换效率。这一结果对于获得新的中红外光源是非常有益的。     

Longitudinal quadratic electro-optical effect in KTN

The occurrence of the longitudinal quadratic electro-optic effect in potassium tantalo niobate (KTN) is reported. It is shown that this effect will occur for particular orientations in all crystals with the point group m3m. Measurements of the halfwave voltage in thin slices of KTN are in good agreement with theory.     

Temperature-independent low-voltage wide-bandwidth optical modulators

Temperature-independent electro-optic modulators have been constructed using lithium niobate. A frequency response extending to 2 GHz has been achieved with a relatively low drive power. The modulators have been used with a 0.63 ?m laser and are easily aligned on a standard optical bench.     

倾斜耦合的光栅耦合器研究进展

近年来,片上光子集成技术备受关注并飞速发展,但在光纤与芯片、芯片与芯片上实现高效、高可靠性的光耦合仍是难题。光栅因其制作简单,位置灵活,对准容差大及可实现片上测试等一系列优点而备受研究者的关注。目前在绝缘体上硅(SOI)平台和绝缘体上铌酸锂(LNOI)平台上已开发出大量的光栅耦合器件,并获得较高的耦合效率和大带宽。该文主要介绍光栅耦合器的工作原理和主要性能指标,阐述了均匀光栅、倾斜光栅、闪耀光栅和切趾光栅耦合的特点及现阶段进展,并对具有代表性的一维光栅性能指标进行了比较。结果表明,分布式布喇格反射镜和金属反射镜可有效地提升光栅耦合效率。此外,该文还介绍了基于 LNOI平台的几种光栅耦合器, 其可帮助研究者们梳理光栅耦合器的发展历程、研究现状及各耦合器的特点,为未来研究提供一定的参考。     

Low-loss CaxBa1−xNb2O6 ridge waveguide for electro-optic devices

Optical ridge waveguide using calcium barium niobate (CBN) on silicon substrate for the first time is designed, fabricated and characterized for future integrated electro-optic devices. To obtain single-mode propagation, the CBN thin strip is designed to be surrounded by thick silicon dioxide layer forming a ridge waveguide. Deposition of CBN film on profiled silicon dioxide introduces spatial separation which solves the CBN etching problem. Fabrication, edge polishing and near-field mode profile measurement of the waveguide are carried out. The measurement is in good agreement with the simulation and an exact loss as low as 2.15 dB/cm was obtained for the fabricated waveguide.     

Optical arbitrary waveform generation based on an array of tunable apodized waveguide Bragg gratings

A structure of optical arbitrary waveform generation (OAWG) based on an array of tunable apodized waveguide Bragg gratings (WBGs) is proposed. The WBGs array on lithium niobate (LN) consists of several apodized gratings, waveguides and electrodes deposited on both sides of gratings and waveguides. The properties of OAWG are analyzed using transfer matrix method. Due to the electro-optic effect of LN, the amplitude and phase of incident light source are controlled via adjusting the voltages on electrodes. Consequently, the optical pulses with different waveforms are obtained and the amplitude is linearly tuned. In addition, voltages compensating amplitude and phase distortion are demonstrated.