We establish the phase diagram for the plasmonics-engineered couplings between whispering gallery modes, and experimentally demonstrate exotic phenomena with an integrated hybrid microresonator, including the engineered dissipative-dispersive couplings, and modal splitting at tens of gigahertz.

Surface-enhanced coherent anti-Stokes Raman scattering (SECARS) technique has triggered huge interests due to the significant signal enhancement for high-sensitivity detection. Previous SECARS work has tended to focus only on the enhancement effect at a certain combination of frequencies, more suitable for single-frequency CARS. In this work, based on the enhancement factor for broadband SECARS excitation process, a novel Fano resonance plasmonic nanostructure for SECARS is studied. In addition to the 12 orders of magnitude enhancement effect that can be realized under single-frequency CARS, this structure also shows huge enhancement under broadband CARS in a wide wavenumber region, covering most of the fingerprint region. This geometrically-tunable Fano plasmonic nanostructure provides a way to realize broadband-enhanced CARS, with potentials in single-molecular monitoring and high-selectivity biochemical detection.

The spin-selective absorption (SSA) usually means absorbing one spin state of a circular polarized (CP) wave while reflecting the orthogonal one. Here, we propose two types (type 1 and type 2) of dual-band SSA with strong circular dichroism based on chiral metasurface operating at the terahertz region. For the proposed dual-band SSA metasurface, type 1 can absorb the same spin state of a CP wave in two adjacent bands, while type 2 can absorb one spin state of a CP wave in the first band and absorb the orthogonal one in the second band. The physical mechanism of the proposed SSA metasurface is discussed by introducing the multiple interference model with a detailed equation derivation process. The theoretically calculated results are well-consistent with the simulated one. Four samples (including two types of dual-band SSA metasurface and their mirrored structure) were fabricated and measured to demonstrate our strategy. Finally, the THz near-field imaging is implemented based on the proposed dual-band SSA metasurface to demonstrate their potential applications in multiband THz CP wave detection and image encryption.

Magneto-optical traps based on grating chips can simplify cold atom physical package architectures significantly. Here we report the design and fabrication of a high-diffraction-efficiency grating magneto-optical trap (GMOT). The numerical simulation is performed with an optimized profile and measured refractive index of the gold film. In the design, the fabrication tolerance is also considered. The fabricated grating chip achieved a diffraction efficiency of up to 40%. Up to 2.8 x 10(7) are trapped with the chip, and the characterization of the GMOT is performed. High absorption contrast CPT resonance signal was also obtained. The proposed atom chip can be leveraged to realize compact cold atom clocks and other cold atom-based quantum sensors.

Microcavity optical frequency comb (also called the microcavity comb), a subversive technology, is an integrated light source produced from a four-wave mixing process in a nonlinear optical microcavity. As a precision device with excellent properties of optical frequency, microcavity combs can be extensively applied in many fields such as molecular spectroscopy, coherent communication, LiDAR, metrology, and lightweight equipment for airborne system. Here, the fabrication of integrated silicon nitride (Si3N4) microcavity optical frequency comb devices was reported. The balance between the stress, thickness and stoichiometry of Si3N4 was well controlled. A reliable method was proposed to fabricate Si3N4 optical film with enough thickness and stoichiometry to meet the requirements of anomalous dispersion and reducing light absorption. The modified technology of Damascene process with microstructures to decline the stress of thick Si3N4 film was developed to reduce defects. Furthermore, the mask via with a 30 nm thick alumina compensation layer was optimized and a practicable etching process was used for fabricating Si3N4 microresonators with sub-15 nm roughness of lateral walls of microring and waveguide. The experimental results show a high quality of Si3N4 microcavity. Additionally, a coherent Kerr optical frequency comb spectrum can be produced with a wide spectral range from 1480 nm to 1640 nm via dual light pumping.

Nanoscale-patterned chromium (Cr) metal structures are widely used in a large variety of semiconductor processing fields. These structures are usually fabricated via the direct etching method. Owing to the drawbacks of traditional lithography techniques (such as electron beam, ion beam, and scanning probe lithography), it is still a high-cost and complex work to accomplish nanoscale structure fabrication. In this paper, through laser heat-mode lithography, a chalcogenide AgInSbTe (AIST) film is chosen as the dry-etching resist to fabricate a series of arbitrary micro/nanostructures on the Cr film. The etching mechanism from the AIST resist to the Cr mask under the Cl2/O2-based gases has been elucidated through energy-dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. A grating pattern with a minimum pitch of 300 nm has been achieved on the Cr mask, and successfully transferred onto a diamond substrate as an X-ray beam splitter. This work provides an effective method for nanoscale structure fabrication and clarifies the antietching mechanisms of AIST resist films under Cl-based plasma etching.

Kerr frequency combs have been attracting significant interest due to their rich physics and broad applications in metrology, microwave photonics, and telecommunications. In this review, we first introduce the fundamental physics, master equations, simulation methods, and dynamic process of Kerr frequency combs. We then analyze the most promising material platform for realizing Kerr frequency combs—silicon nitride on insulator (SNOI) in comparison with other material platforms. Moreover, we discuss the fabrication methods, process optimization as well as tuning and measurement schemes of SNOI-based Kerr frequency combs. Furthermore, we highlight several emerging applications of Kerr frequency combs in metrology, including spectroscopy, ranging, and timing. Finally, we summarize this review and envision the future development of chip-scale Kerr frequency combs from the viewpoint of theory, material platforms, and tuning methods.

Cold-atom systems provide a nearly static measurement medium with almost no interaction between the atoms for quantum precision measurement processes, thereby avoiding the frequency shift and broadening existing in the working medium of hot atoms, making the measurement results more accurate. However, the atomic cooling part of current quantum precision measurement systems is bulky and complex, which is not conducive to miniaturization of distributable quantum measurement standard systems. In order to make a less complex magneto-optical trap system, we adopted the scheme to combine the diffraction grating chip and the atomic cooling technique. The wavefront of a single incident light was phase modulated through the linear grating, and the atoms were successfully trapped on a chip scale. The preparation of the core chip of a miniaturized magneto-optical trap and the realization of the magneto-optical trap system with a simple optical structure can lay a solid foundation for further miniaturization of the overall system of a magneto-optical trap in the future.

Negative magnetoresistance (MR) is not only of great fundamental interest for condensed matter physics and materials science, but also important for practical applications, especially magnetic data storage and sensors. However, the microscopic origin of negative MR is still elusive and the nature of the negative MR in magnetic topological insulators has still not been completely elucidated. Here, we report magnetotransport studies on Cr doped (Bi1-x Sb x )2Te3 topological insulator thin films grown by magnetron sputtering. At the temperature of 2 K, a giant negative MR reaching 61% is observed at H = 2 T. We show that the negative MR is closely related to the position of the Fermi level, and it reaches the maximum when the Fermi level is gated near the charge neutral point. We attribute these results to the Coulomb potential due to the random composition fluctuations in Cr doped (Bi1-x Sb x )2Te3. Our results provide a deeper insight into the mechanism of negative MR, and are helpful to realize the quantum anomalous Hall effect in the sputtered Cr-(Bi1-x Sb x )2Te3 thin-film systems by tuning the Fermi level and reducing disorder effects.

Laser heat-mode lithography is an important method for the fabrication of micro and nanostructure. A metal lift-off method through hyperbolic undercut of laser heat-mode lithography was proposed. In this method, a desirable hyperbolic undercut profile was used to replace the inverted trapezoid undercut, and the hyperbolic undercut profile can be obtained through laser heat-mode lithography technique. Cr structures of gratings, grids and planar spiral inductor with a minimum linewidth of 0.42 mu m and a height of 100 nm were obtained successfully. These indicate that the lift-off process through hyperbolic undercut of laser heat-mode lithography can be used to fabricate the submicron metal structures. (C) 2020 Elsevier B.V. All rights reserved.

The optical blue filter with the suitable bandwidth, high transmittance and large acceptance angle is usually regarded as a critical optical component for a variety of applications. Here, we propose a polarization-insensitive angle-tolerant hybrid plasmonic blue filter incorporating two-dimensional aluminum (Al) nanodisks on the top of planar waveguide. The proposed plasmonic filter works via hybridization of surface plasmon polariton (SPP) mode, the localized Fabry–Perot resonance and waveguide mode, thus enables high peak transmittance up to 70% with the bandwidth of 30 nm and large acceptance angle up to 20°.

This study simulates the surface-tip-enhanced Raman scattering (SERS-TERS) model of a stepped tip with a silver film and a silver-nanoparticle-active substrate. The simulation is established by the finite-difference time-domain method. The near-field electric field distributions of different types of needle tips and substrates arc numerically calculated under the same conditions, verifying the effectiveness of the designed method in the Raman scattering enhancement. Next, the electric field intensity of the model is systematically analyzed under different influencing factors: the curvature radius of the tip, the thickness and height of the silver film on the tip, the diameter of the silver nanoparticles, the gap between the tip and the silver nanoparticles, and the incident angle. The field enhancement factor is maximized at a tip-curvature radius of 5 nm, a silver-film thickness of 25 nm, a silver-film height of 300 nm, a silver-nanoparticle diameter of 55 nm, a 1 nm gap between the tip and silver nanoparticles, and an incident angle of 45 degrees. The largest enhancement factor is of the order of magnitude of 10(7). The simulation results provide an important theoretical basis and experimental guidance for preparing high-efficiency tip and TERS active substrate structures.

This article proposes a surface-plasmon-enhanced GaN-LED based on the multilayered rectangular nano-grating. This structure contains a SiO2 film, an Ag film and a HfO2 film sequentially coated on the rectangularly-patterned p-GaN layer. The Ag film is used to enhance the internal quantum efficiency. The HfO2 cover-layer symmetrizes the distribution of refractive index besides the Ag film to improve the light extraction efficiency and surface-plasmon (SP) extraction efficiency. The inserted SiO2 layer is utilized to further improve the SP extraction efficiency. The properties of SP modes and Purcell effect in this structure are investigated. The photoluminescence experiments demonstrate that its peak intensity of top-emission is about 2.5 times greater than that from the reference structure covered by a single-layer Ag film on the rectangularly-patterned p-GaN layer.

Metallic nanostructures can enhance light-matter interaction arising from the surface plasmonic resonances,which is highlight on optics for many applications.A tunable optical property can be induced by plasmonic resonance,leading to the significant electromagnetic field enhancement,as well as the position of the "hot spot" at a tiny nanogap.Analogue of the diffractive optics,an alternative method of multiscale cascaded field enhancement with a simple metallic nanostructure,double stacked nanocone (DSC),was proposed in the article.In detail,a tunable hybrid mode was achieved from the strong interference between a fundamental plasmonic cavity mode and a plasmonic gap mode.Furthermore,it led to a far-field optical response at a certain wavelength.The position of the hot spots can also be mounted on the top surface of the DSC nanostructure.Additionally,a technique of mask reconfiguration was developed to precisely fabricate the multiscale DSC nanostructure,which can benefit to construct the necessary three steps in the nanostructure.The experimental results also provide a substantial evidence to demonstrate the art-of-state of the multiscale cascaded field enhancement,as well as the technique of nanofabrication.

The surface topography of micro-structures would significantly affect the products quality and industrial performance of micro-nano devices [1]. In recent years, the application of micro-structures in Micro Electro Mechanical Systems (MEMS) and integrated circuit is more and more widely. How to reflect the 3D surface topography of these micro structures accurately and measure the surface’s parameters precisely as well as quickly are becoming a hot research area of precision measurement. White-light interference microcopy technology is one of the most widely used non-contacting measurement methods at present, which has the advantages of nondestructive, fast measurement and high accuracy, has been widely applied in surface topography measurement of micro structures. In this paper, an analysis method of microstructure surface topography algorithm based on wavelet filter to analyze white interference signals is proposed, this method utilizes R/G/B three channels color information which is significantly superior to traditional black and white imaging process method. The experimental results shows that this method has good accuracy and repeatability in 3D surface measurement.

纳米压印光刻技术具有低成本、高效率、大面积、高分辨、多尺度、良好的工艺兼容性等特点,可用于亚波长光电子器件的研究.提出了硅水合物(HSQ)/聚丙烯酸甲酯(PMMA)双层胶室温纳米压印工艺方法,研究并解决了有关压印光刻胶剩余底膜和纳米图形保真性刻蚀转移的两个关键工艺技术问题.以制备特定需求的石英纳米光栅器件为目标,经过工艺优化,成功地实现了周期200 nm、占空比0.5、深宽比5∶1、栅线侧壁垂直且粗糙度小于3 nm的高分辨率亚波长光栅的制备.所提出的双层胶刻蚀方法,有望拓展到纳米标准物质和芯片级光学频率梳器件等对侧壁陡直和粗糙度有严格要求的应用领域.

A new tip-enhanced Raman scattering(TERS) model was established by finite difference time domain (FDTD) method, which included a conical tungsten tip with concave arc and silver-coated and a gold nanoparticle. The enhancement effectandparameter optimizationof the TERS model wereinvestigated. Under 632. 8 nmwavelength laser excitation, three-dimensional electromagnetic simulations were carried out for the TERS effect with different conditions, and the simulation resultswerepresented and discussed. The results indicate that this TERS model has the maximum field enhancement factor when the incident angle is 72 degrees, the sample diameter is about 140 nm and the tip sample gap is reach 2 nm. The conclusion provides a reference for developing higher efficiency enhancingmetal tips and the Raman spectrometer with best performance.

Visible light communication (VLC) based on light emitting diodes has been regarded as an effective complement to radio frequency signal transmission. The color filter in VLC system plays the pivotal role for boosting signal-noise-ratio. In this paper, a tri-band color transmission filter with bandwidths consisting with LED's 30nm is designed based on guided mode resonance, incorporating a sub-wavelength aluminum grating on slab dielectric waveguide made of titanium dioxide on silica substrate. Parameters of grating structure, including the grating period, duty cycle, grating thickness, and waveguide thickness, are optimized by employing particle swarm optimization toolbox. The far field spectrum is calculated by rigorous coupled-wave analysis to verify the effectiveness of the designed filter. Three center-wavelength of transmission bands are 440nm, 530 and 630 nm. The full-width-at-half-maximum (FWHM) bandwidths of three bands are about 30nm which consist with LED's bandwidth.

2017年9月,由中国计量科学研究院牵头、13家单位联合申报的“芯片级计量标准关键技术研究”项目获“国家质量基础的共性技术研究与应用”重点专项(以下简称NQI)支持.NQI专项总体部署按照“面向国际科技前沿、面向国家重大需求和国民经济主战场”3个基本原则确定,“芯片级计量标准关键技术研究”项目对应于其中的高准确度标准物质与量值扁平化传递的研究方向.

Multistep plasmonic nanostructures can induce the deep modulation of electromagnetic-field interactions on the nanoscale for positioning hotspots, and this generation of enhanced fields is important in many optical applications. In this article, a new strategy is proposed for fabricating a plasmonic doublestacked nanocone (DSC) nanostructure. In the DSC structure, a tunable plasmonic hybrid mode proceeds from the strong coupling of the plasmonic resonance of a fundamental cavity mode with a localized surface plasmon gap mode. In the nanostructure, the far-field response is deeply modulated and the hottest spots can be effectively positioned on the top surface of the DSC nanostructure. A controllable and cost-effective mask-reconfiguration technique for manufacturing the multiscale nanostructure is developed, which guarantees the generation of the introduced crucial stage on the DSC nanostructure. To evaluate the features of the plasmonic resonance, the DSC nanostructure is used as a surface-enhanced Raman scattering (SERS) substrate for detecting 4-mercaptopyridine molecules under specific excitation conditions. Its good performance, with an average measured SERS enhancement factor as high as 108, demonstrates its strong plasmonic-mode hybridization and extreme field enhancement.