Second Harmonic Light Manipulation with Vertical Split Ring Resonators

The second harmonic generation (SHG) of vertical and planar split‐ring resonators (SRRs) that are broken centro‐symmetry configurations at the interface of metal surface and air is investigated. Strong interactions, better electromagnetic field confinements, and less leakage into the substrate for vertical SRRs are found. Experimental results show a 2.6‐fold enhancement of SHG nonlinearity, which is in good agreement with simulations and calculations. Demonstrations of 3D metastructures and vertical SRRs with strong SHG nonlinearity majorly result from magnetic dipole and electric quadrupole clearly provides potential applications for photonics and sensing.     

Testing Aspherics in Reflected Light Using Blazed Synthetic Holograms

It is shown that blazed computer generated holograms having a rotational symmetry (RSH) are especially suitable for interferometers working in reflected light which can be used in testing aspherics. The RSH acts either as a null lens of a very complex kind or it is used not only as beam splitter but also as beam combiner. From a more technical point of view, the latter version is especially interesting although in this case parasitic light caused by the double passage of all beams through the RSH may spoil the interference pattern. The two versions were tested experimentally. So, a Twyman-Green interferometer, on the basis of a blazed RSH, was built and tested. The interference pattern was free from severe disturbances because of the double passage through the RSH. Also a Fizeau interferometer was tested where the RSH acts as beam splitter and reunifer. Here the disturbances were more severe owing to the fact that the zero order as well as one first order of diffraction must be used. Possibilities for the suppression of stray light in this type of interferometer are discussed.     

Imaging through Nonlinear Metalens Using Second Harmonic Generation

The abrupt phase change of light at metasurfaces provides high flexibility in wave manipulation without the need for accumulation of propagating phase through dispersive materials. In the linear optical regime, one important application field of metasurfaces is imaging by planar metalenses, which enables device miniaturization and aberration correction compared to conventional optical microlens systems. With the incorporation of nonlinear responses into passive metasurfaces, optical functionalities of metalenses are anticipated to be further enriched, leading to completely new application areas. Here, imaging with nonlinear metalenses that combine the function of an ultrathin planar lens with simultaneous frequency conversion is demonstrated. With such nonlinear metalenses, imaging of objects with near infrared light while the image appears in the second harmonic signal of visible frequency range is experimentally demonstrated. Furthermore, the functionality of these nonlinear metalenses can be modified by switching the handedness of the circularly polarized fundamental wave, leading to either real or virtual nonlinear image formation. Nonlinear metalenses not only enable infrared light imaging through a visible detector but also have the ability to modulate nonlinear optical responses through an ultrathin metasurface device while the fundamental wave remains unaffected, which offers the capability of nonlinear information processing with novel optoelectronic devices.     

Second Harmonic Generation in a Free Electron Laser

It is pointed out that in a free electron laser higher frequencies, which are very nearly equal to the harmonics, are generated. Second harmonic generation, in stimulated emission in a spatially periodic static magnetic field, is studied using the Feynman diagram technique. The ratio of gain for the second harmonic compared to that of the fundamental harmonic is of the order of 10 ^?9 for the conditions present in the free electron laser of Deacon et al. [1].     

Ka波段二次谐波回旋速调管放大器的优化设计与分析

设计了一支Ka波段二次谐波回旋速调管放大器,并利用基于广义电报方程的时域自洽非线性理论模型,对设计的回旋速调管进行了数值模拟.详细分析了工作电流、横纵速度比和磁场等参数对放大器输出功率、增益和效率的影响,得到了最佳的工作参数.模拟结果表明,在电子注电压70kV,电流15 A,磁场0.675 T附近,可以获得大于250 kW的输出功率,近26％的效率和440 MHz的带宽.     

Bismuth Ferrite Second Harmonic Nanoparticles for Pulmonary Macrophage Tracking

Recently, second harmonic generation (SHG) nanomaterials have been generated that are efficiently employed in the classical (NIR) and extended (NIR‐II) near infrared windows using a multiphoton microscope. The aim was to test bismuth ferrite harmonic nanoparticles (BFO‐HNPs) for their ability to monitor pulmonary macrophages in mice. BFO‐loaded MH‐S macrophages are given intratracheally to healthy mice or BFO‐HNPs are intranasally instilled in mice with allergic airway inflammation and lung sections of up to 100 μM are prepared. Using a two‐photon‐laser scanning microscope, it is shown that bright BFO‐HNPs signals are detected from superficially localized cells as well as from deep within the lung tissue. BFO‐HNPs are identified with an excellent signal‐to‐noise ratio and virtually no background signal. The SHG from the nanocrystals can be distinguished from the endogenous collagen–derived SHG around the blood vessels and bronchial structures. BFO‐HNPs are primarily taken up by M2 alveolar macrophages in vivo. This SHG imaging approach provides novel information about the interaction of macrophages with cells and the extracellular matrix in lung disease as it is capable of visualizing and tracking NP‐loaded cells at high resolution in thick tissues with minimal background fluorescence.     

Metrology of Multiphoton Microscopes Using Second Harmonic Generation Nanoprobes

In multiphoton microscopy, the ongoing trend toward the use of excitation wavelengths spanning the entire near‐infrared range calls for new standards in order to quantify and compare the performances of microscopes. This article describes a new method for characterizing the imaging properties of multiphoton microscopes over a broad range of excitation wavelengths in a straightforward and efficient manner. It demonstrates how second harmonic generation (SHG) nanoprobes can be used to map the spatial resolution, field curvature, and chromatic aberrations across the microscope field of view with a precision below the diffraction limit and with unique advantages over methods based on fluorescence. KTiOPO4 nanocrystals are used as SHG nanoprobes to measure and compare the performances over the 850–1100 nm wavelength range of several microscope objectives designed for multiphoton microscopy. Finally, this approach is extended to the post‐acquisition correction of chromatic aberrations in multicolor multiphoton imaging. Overall, the use of SHG nanoprobes appears as a uniquely suited method to standardize the metrology of multiphoton microscopes.     

Quasicrystal Photonic Metasurfaces for Radiation Controlling of Second Harmonic Generation

Photonic metasurfaces, a kind of 2D structured medium, represent a novel platform to manipulate the propagation of light at subwavelength scale. In linear optical regime, many interesting topics such as planar meta‐lenses, metasurface optical holography, and so on have been widely investigated. Recently, metasurfaces have gone into the nonlinear optical regime. While it is recognized that the local symmetry of the meta‐atoms plays a vital role in determining the polarization, phase, and intensity of the nonlinear waves, much less attention has been paid to the global symmetry of the nonlinear metasurfaces. According to the Penrose tiling and the newly proposed hexagonal quasicrystalline tiling, nonlinear optical quasicrystal metasurfaces are designed and fabricated based on the geometric‐phase‐controlled plasmonic meta‐atoms with local rotational symmetry. It is found that the far‐field radiation behavior of second harmonic generation waves are determined by both the tiling schemes of quasicrystal metasurfaces and the local symmetry of meta‐atoms they consist of. The proposed concept may open new avenues for designing nonlinear optical sources with metasurface crystals.     

Second Harmonic Generation in Ion Implanted Lithium Niobate Planar Waveguides

Abstract

We report the first demonstration of second harmonic generation (SHG) in ion implanted lithium niobate optical waveguides. For both ordinary and extraordinary index profiles a computer program was developed to simulate the positions of the modes within the optical well. With the help of this program the theoretical possibility of SHG using mode matching conditions within the guide was then studied as a function of the guide depth and temperature, and from these predictions, practical guides were constructed. Initially, SHG Cerenkov radiation was observed with leaky single implanted guides. Mode matched SHG from m = 0 to m = 2 was subsequently achieved by means of a multiple energy implant which was able to confine both fundamental and harmonic waves. Allowing for coupling and transmission losses, the corrected conversion efficiency is 0–018% W^?1 which compares favourably to a theoretical prediction for this guide of 0–020% W^?1. In this case a wide temperature tuning range was obtained.     

二次谐波在二维材料结构表征中的应用

二次谐波作为非线性光学的重要分支,逐渐成为表征晶体结构的重要手段之一。在众多表征方法中,二次谐波因其无损检测、高稳定性、可调谐性、超快响应、偏振敏感性、通用性、操作简单等特点被广泛应用于二维材料结构表征,为二维材料的物性研究和功能应用提供了重要信息,大大推动了二维材料基础研究的快速发展。本文综述了近几年二次谐波在二维材料结构表征中的研究,简述了二次谐波产生原理,介绍了飞秒激光器接入共聚焦拉曼光谱仪产生二次谐波测试装置,分别讨论了二次谐波在二维材料的层间堆垛层数、层间堆垛角度、单层二维材料晶界及晶体取向表征方面的应用。同时,本文还介绍了采用二次谐波强度直接、灵敏地检测晶体中应变幅度以及通过二次谐波信号变化跟踪材料中的缺陷变化,接着讨论了二次谐波与拉曼光谱、光致发光的多维度关联分析在材料全面深度表征方面的重要性。最后展望了二次谐波未来在材料结构表征中的潜在研究方向。     

Second Harmonic Generation in Optical Fibres: Multiphoton Absorption and Translation-inversion Symmetry

Abstract

Multiphoton absorption provides a route to x ₍₂₎ grating formation in optical fibres. It explains the efficacy of ‘seeding’ the fibre with green light to induce fibre second harmonic generation. The process depends on absorption sites with spatially inverted configurations having different multiphoton absorption rates.     

Review of Second Harmonic Generation Measurement Techniques for Material State Determination in Metals

This paper presents a comprehensive review of the current state of knowledge of second harmonic generation (SHG) measurements, a subset of nonlinear ultrasonic nondestructive evaluation techniques. These SHG techniques exploit the material nonlinearity of metals in order to measure the acoustic nonlinearity parameter, \(\beta \). In these measurements, a second harmonic wave is generated from a propagating monochromatic elastic wave, due to the anharmonicity of the crystal lattice, as well as the presence of microstructural features such as dislocations and precipitates. This article provides a summary of models that relate the different microstructural contributions to \(\beta \), and provides details of the different SHG measurement and analysis techniques available, focusing on longitudinal and Rayleigh wave methods. The main focus of this paper is a critical review of the literature that utilizes these SHG methods for the nondestructive evaluation of plasticity, fatigue, thermal aging, creep, and radiation damage in metals.     

Photoinduced Second Harmonic Generation of Bi2S3 Microcrystallite Doped Silica Glass

Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 μm and frequency doubled laser beams from a mode-locked Nd: YAG laser. It was found that the signal intensity increased with the irradiating time and approached a saturation gradually. The effect may be explained reasonably by the DC field model.     

球式自动平衡装置在二倍频激励下的动态特性

高速旋转机械是应用较多的一种机械设备,一旦发生故障造成的损失十分严重。解决的办法之一就是对其转子进行自动平衡。生产中转子除了受到偏心激振力之外,还会受到高次倍频激振力和分数倍频激振力,特别是二倍频激振力。研究这些激振力对球式自动平衡装置的影响有非常重要的意义。由此,构建球式自动平衡装置在二倍频激振力作用下的平衡方程,应用Matlab软件研究和通过实验验证其动态特性。     

On the Redefinition of the Second and the Velocity of Light

This summary article resulted from an informal discussion period held during the International Conference on Precision Electromagnetic Measurements, August 14-17, 1962. This session was presided over by Prof. Norman Ramsey of Harvard University. The Radio Standards Laboratory of the National Bureau of Standards in Boulder, Colorado, sponsored the meeting along with the IRE Professional Group on Instrumentation and the AIEE Instrumentation Division. Partial support for the conference came from a grant from the National Science Foundation.     

Self-induced Temperature Profile and Inhomogeneity Effect on Second Harmonic Generation Using Focused Laser Beam

The behaviour of optical second harmonic due to crystal inhomogeneity and self-induced thermal effect has been considered for a focused laser beam. Temperature profile created due to a fundamental laser beam along the crystal length shows an increase in temperature band width for various values of focusing parameter. Normalized second harmonic power in inhomogeneous crystals increases up to an optimum value of focusing parameter. Utility of focusing is limited due to formation of filament in crystal for higher values of focusing parameter.