Formation and control of Turing patterns and phase fronts in photonics and chemistry

We review the main mechanisms for the formation of regular spatial structures (Turing patterns) and phase fronts in photonics and chemistry driven by either diffraction or diffusion. We first demonstrate that the so-called ‘off-resonance’ mechanism leading to regular patterns in photonics is a Turing instability. We then show that negative feedback techniques for the control of photonic patterns based on Fourier transforms can be extended and applied to chemical experiments. The dynamics of phase fronts leading to locked lines and spots are also presented to outline analogies and differences in the study of complex systems in these two scientific disciplines.     

AlGaN-based high-performance metal–semiconductor–metal photodetectors

Design, structure growth, fabrication, and characterization of high performance AlGaN-based metal–semiconductor–metal (MSM) photodetectors (PD) are reported. By incorporating AlN nucleation and buffer layers, the leakage current density of GaN MSM PD was reduced to 1.96 × 10⁻¹⁰ A/cm² at a 50 V bias, which is four orders of magnitude lower compared to control devices. A 229 nm cut-off wavelength, a peak responsivity of 0.53 A/W at 222 nm, and seven orders of magnitude visible rejection was obtained from Al_0.75Ga_0.25N MSM PD. Two-color monolithic AlGaN MSM PD with excellent dark current characteristics were demonstrated, where both detectors reject the other detector spectral band with more than three orders of magnitude. High-speed measurements of Al_0.38Ga_0.62N MSM PD resulted in fast responses with greater than gigahertz bandwidths, where the fastest devices had a 3-dB bandwidth of 5.4 GHz.     

Controlled optical manipulation and sorting of nanomaterials enabled by photonic and plasmonic nanodevices

Precise manipulation and sorting of nanomaterials cannot rely on techniques used for micro- and macro-scale objects because of their nanoscale size, which is smaller than the diffraction limit, and their fast Brownian diffusion. To overcome the limitations of standard optical tweezers, new techniques have recently emerged that make use of optical forces acting on nanomaterials in the vicinity of photonic and plasmonic nanostructures. This review focuses on the techniques that have been recently developed to either optically transport, sort, trap, rotate, assemble, or deposit nanomaterials using photonic or plasmonic devices. The first part is dedicated to the optical transport and sorting of nanomaterials using photonic waveguides. The second part provides an overview of the recent work on optical trapping and manipulation of nanomaterials using photonic and plasmonic nanoresonators. The third part provides a short summary of recent work on optical trapping and manipulation using metalenses and metasurfaces. This review aims to highlight some specific functionalities enabled by photonic and plasmonic devices that make it possible to tailor the optical forces acting on nanomaterials.     

面向可见光通信的硅基InGaN/GaN多量子阱多口分路器光子集成芯片

为研究面向可见光通信的多功能光子集成芯片,实现可见光信号发射、探测、传输和功率分配的一体化的复合功能,该文提出一种基于硅基InGaN/GaN多量子阱材料的微型发光二极管(LED)多口分路器结构的光子集成芯片,对集成芯片进行了形貌、光电特性和可见光通信测试等多方面表征,实现了对可见光信号的有效传输和不同比例的多口功率分路,并对分路器不同端口的出射光强进行量化处理,最后,利用信号发生器在微型LED光源发射端加载300 kHz的矩形波电信号,收集分路器末端发射的调制可见光信号,输入/接收信号的波形变化趋势一致,说明该光子集成芯片可实现有效的可见光通信。该研究的主要目的是尝试性将可见光波段的光源和光电探测器集成在氮化物晶圆上,为可见光通信的全光网络的可见光信号片上集成式处理提供新的研究思路和方案,为发展面向可见光通信网络需求的复合功能光子集成芯片终端提供了更多可能性。     

基于光子学的微波移频方法研究

微波移频技术(MFS)广泛应用于电子对抗、卫星通信、频控阵雷达等系统。基于光子学的微波移频方法具有带宽大、频谱纯净等优点。为了探索基于光子学的微波移频性能,该文对比研究了基于声光移频(AOFS)、锯齿波相位调制(SPM)和I/Q调制3种微波光子移频方法,阐释了3种方法的原理,搭建了对应的原理验证系统,对不同的移频方法进行了实验与分析。结果表明,3种移频方法都可以实现精准的微波信号移频,实现大于30 dB的杂散抑制比。但3种移频方法也存在各自的局限性：AOFS的工作频率、带宽和移频方向较为固定,可调谐性低;SPM移频与I/Q调制对输入驱动信号要求严格,系统稳定性较差。     

Engineered Light Scattering in Colloidal Photonic Heterocrystals

Photonic heterocrystals are prepared by sandwiching films of self‐assembled opal and force‐assembled Langmuir–Blodgett colloidal crystals. Anomalously strong light scattering in conjunction with low reflectivity is observed with increasing angle of incidence in the spectral range of photonic bandgaps. The occurrence of light scattering at the interface has been assigned to the optical mode mismatch between the two types of photonic crystals. Photonic bandgap‐related mechanisms of trapping the decaying photonic crystal modes at the interface are suggested.     

Extrusion-based Integrative Chemistry: Generation and applications of inorganic fibers

In this review we depict how fibers can be obtained by combining sol-gel and polymer chemistry with extrusion processes acting as an external shaping mode. Thanks to this Integrative Chemistry-based synthetic path, it was possible to organize nano-building blocks such as V₂O₅ ribbons and ZnO nanorods on a greater length scale yielding highly anisotropic fibers. It has been demonstrated that when aligning a whole population of nano-building block objects along a single main axis, collective properties were obtained, thereby enhancing their sensing, mechanical or photonic properties. This method can be extended toward fiber morphogenesis by using isotropic nanoparticles such as TiO₂, and can be scaled-up toward the one-step generation of several hundred meter long fibers with both high surface to volume ratio and high surface roughness. Specifically, when addressing photocatalytic-based VOC pollutant degradation, these TiO₂ fibers appear to be outstanding candidates regarding both pollutant degradation and associated mineralization (production of water and carbon dioxide).     

Frequency-conversion properties of Eu doped chlorophosphate glass ceramics containing CaCl2 nanocrystals

Eu³⁺ ion doped chlorophosphate glass ceramics containing nanocrystals were successfully prepared, and their spectroscopic characterizations were done using absorption, excitation and emission spectra. For the crystallized samples, X-ray diffraction (XRD) and transmission electron microscopy (TEM) experiments evidenced the formation of CaCl₂ nanocrystals. The absorption and emission spectra investigations indicate that a considerable amount of Eu³⁺ ions was trapped in CaCl₂ nanocrystals, and therefore an efficient up- and down-frequency conversion was observed. The comparative spectroscopic studies of Eu³⁺ doped samples suggest that the investigated glass ceramics systems are potentially applicable as frequency-conversion photonics devices.     

光子学的发展和光子产业

论述了光子学、光子技术的产生、发展和突破;阐明了光子学的定义、内涵、范畴和前沿;提出了关于第1类和第Ⅱ类光子产业的设想;予测了光子产业发展.