Continuous-Wave Raman Lasing from Metal-Linked Organic Dimer Microcrystals

Stimulated Raman scattering offers an alternative strategy to explore continuous-wave (c.w.) organic lasers, which, however, still suffers from the limitation of inadequate Raman gain in organic material systems. Here we propose a metal-linking approach to enhance the Raman gain of organic molecules. Self-assembled microcrystals of the metal linked organic dimers exhibit large Raman gain, therefore allowing for c.w. Raman lasing. Furthermore, broadband tunable Raman lasing is achieved in the organic dimer microcrystals by adjusting excitation wavelengths. This work advances the understanding of Raman gain in organic molecules, paving a way for the design of c.w. organic lasers.     

氧离子注入隔离的全内反射型光波导开关

研制了一种全内反射型InGaAsP/InP光波导开关。采用氧离子注入形成的高阻特性来作为载流予注入区的隔离。由此获得陡峭的反射面,改善了光开关的性能。在入射光波长为1.3um,注入电流为32mAT得到光开关反射端消光比为18dB,无注入时的关态串话为-19dB.     

Novel optical packet with non-return-to-zero label and duobinary carrier-suppressed return-to-zero payload

A novel packet format with non-return-to-zero (NRZ) label and duobinary carrier-suppressed return-to-zero (DCS-RZ) payload is proposed for optical packet switching networks.NRZ label is followed by DCS-RZ payload with a certain guard time.The spectra of the low-rate NRZ label locate around the optical carrier frequency where some parts of the corresponding spectra of the high-rate DCS-RZ payload have been suppressed due to DCS-RZ modulation.At the switching node,the label or payload extraction can be realized simply through an optical bandpass or notch filter respectively.The feasibility of the scheme is verified by the simulation on the famous photonic design platform designed by Virtual Photonics Inc.(VPI).The effects of optical filter bandwidth on the received signal quality are discussed by analyzing bit error rate(BER)and contrast ratio performances.     

高下路空气孔型光子晶体环形谐振腔的设计

提出一种基于二维正方晶格光子晶体空气孔型高下路效率的环形谐振腔,通过压缩线缺陷波导的宽度实现单模有效控制,同时讨论内围光子晶体列数对传输场的影响,然后运用二维时域有限差分方法数值分析了耦合强度及环区局部折射率调制对下路效率、品质因子以及下路波长等参量的影响.结果表明:当波导宽度为0.7个晶格常量,耦合强度为0个晶格常量,在信道波长为1 528.1 nm时,下路效率为99%,品质因子Q为379;当耦合强度提高到1个晶格常量,下路波长稍微漂移为1 524.3 nm,品质因子显著提高到1 397,而下路效率下降为89%.同时,下路波长会随着环区折射率的增加呈线性红移.     

Photonic crystal LEDs – designing light extraction

Photonic crystals (PhCs) have attracted much attention during the last decade as a solution to overcome the low extraction efficiency of as‐grown light‐emitting diodes (LEDs). In this review we describe the underlying physics and summarize recent results obtained with PhC LEDs. Here, the main focus is on diffracting PhC. In order to quantify the benefit from the incorporation of PhCs for diffracting light a comparison by simulations between a PhC LED and a standard state‐of‐the‐art LED is carried out. Finally, the impact of the PhC on the LEDs emission characteristics will be discussed with respect to étendue‐limited applications.     

光子学及其讨论

本文简述了光子学提出后,国内外的反响。并就处理高速摄影与光子学的关系问题,提出了“高速光子学”,把它作为光子学的一个分支。这个分支的主要研究对象是高速过程或超快现象,并以时间—空间分辨方式提供信息。末了,探讨了光子学本身的发展前景:随着光计算机研究工作的进展和实现,将确立光子学的牢固地位。     

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.     

Structural symmetry of two-dimensional metallic arrays: Implications for surface plasmon excitations

We report our recent investigation of the (0, ±1)-type SPP excitation of a gold two-dimensional nano-cavity array using finite-difference time-domain methodology. Our particular focus is on the symmetry properties of (0, ±1)-SPPs excited by different polarizations of light. Based on a group theory approach, we have shown that these (0, ±1) modes are originated from different symmetry modes at the Γ-point, and the B-(0, ±1) dispersion curve converges to the A-(−1, 0) dispersion curve at the Γ-point. This indicates these (0, ±1) modes are very different in their symmetry properties. As a result, the control of polarization may provide important insights into the manipulation of SPPs.     

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.