Theoretical model of a planar integrated refractive index sensor based on surface plasmon-polariton excitation

A theoretical model of a new integrated planar surface plasmon-polariton (SPP) refractive index sensor is presented and comprehensively investigated. The main principle of operation of this device is based on high efficiency energy transfer between a p-polarized guided mode propagating in a waveguide layer of the structure and the SPP propagating in the opposite direction in a metal layer separated from the waveguide layer by a dielectric buffer. The high efficiency energy transfer is realised by means of a properly designed Bragg grating imprinted in the waveguide layer. This device is compact, free from any moving parts and can easily be integrated into any planar scheme. Our simulations for the sensor operating at the well developed and commercialised telecom wavelengths are based on coupled mode theory.     

Novel surface vibrational spectroscopy: infrared-infrared-visible sum-frequency generation

A novel type of surface vibrational sum-frequency generation spectroscopy is presented that enables a highly specific measurement of the coupling of molecules on surfaces. With this doubly vibrationally resonant technique, two-dimensional vibrational spectroscopy of molecules on surfaces becomes possible. The technique is demonstrated for the C-O stretch vibration of CO on a ruthenium (001) surface. It allows for the determination of the intermolecular coupling strength of dipole-coupled CO molecules on the surface.     

Giant enhancement of second-harmonic generation from a nanocavity metasurface

Nonlinear plasmonic metasurfaces are compatible with complementary metal oxide semiconductor technology and highly promising for on-chip optical switching and modulations and nanoscale frequency conversions. However, the low nonlinearoptical response of metasurface devices limits their practical applications. To circumvent this constraint, we propose the design of a nanocavity plasmonic metasurface, in which the strong light localization in the nanocavity can be used to boost the efficiency of second-harmonic generation. Compared with the single-layer counterpart, experimental results show that the intensity of the second-harmonic waves in the nanocavity metasurface is enhanced by ~790 times. The proposed nanocavity plasmonic metasurfaces in this work may open new routes for developing highly efficient nonlinear metacrystals for on-chip nonlinear sources,nonlinear image encryption, information processing, and so on.     

Enhancing the yield in surface sum-frequency generation by the use of surface polaritons

Received: 23 December 1998     

Ultrafocusing of surface plasmon-polariton in a narrowing concave gap

In a concave gap between flat and cylindrically convex metallic surfaces, surface plasmon-polariton may be localized in nanoscale in conditions of adiabatic narrowing of the gap minimum width and convex curvature radius. Waveguide channels of this type may serve, due to small losses, as an elemental basis for creation of high-speed nanoscale optical circuits.     

Theory of second harmonic generation at a metal surface with surface plasmon excitation

Theory of second harmonic generation at a metal surface is developed, when surface plasmon-polaritons are resonantly excited by the incident electromagnetic field. For harmonic generation from small metallic spheres characterized by the dielectric function ?₁(ω) + i?₂(ω), the resonant enhancement of the second harmonic intensity is predicted to be of the order of ($\text{?}{}_1\text{?}{}_2\text{)}{}^4$. The resonant enhancement is much smaller for the case of a metallic grating.     

Channel plasmon-polariton in a triangular groove on a metal surface

One-dimensional localized plasmons (channel polaritons) guided by a triangular groove on a metal substrate are investigated numerically by means of a finite-difference time-domain algorithm. Dispersion, existence conditions, and dissipation of these waves are analyzed. In particular, it is demonstrated that the localization of the predicted plasmons in acute grooves may be substantially stronger than what is allowed by the diffraction limit. As a result, the predicted waves may be significant for the development of new subwavelength waveguides and interconnectors for nano-optics and photonics.     

Efficient sum-frequency generation of continuous-wave single-frequency coherent light at 252 nm with dual wavelength enhancement

Highly efficient frequency conversions were conducted to obtain deep-ultraviolet single-mode coherent light by use of two-stage external cavities. A power of 154 mW at approximately 252 nm was obtained with a conversion efficiency of more than 8% by doubly resonant sum-frequency mixing of 373-nm light from the first-stage conversion and 780-nm light from a single-mode Ti:sapphire laser. The output performance of the deep-ultraviolet light source is sufficient for use in the laser cooling of neutral silicon atoms.     

Conical sum-frequency generation in a bulk anomalous-like dispersion medium

We observe conical sum-frequency generation in a bulk anomalous-like dispersion medium, which is attributed to complete phase-matching of one fundamental wave and the scattering wave of the other fundamental wave.In addition, efficient sum-frequency output is achieved making use of total internal reflection with conversion efficiency of 7.9% by only one reflection. The experiment proposes a new phase-matching mode under an anomalous-like dispersion condition, which suggests potential applications in efficient frequency conversion.     

Size dependence of light-field enhancement caused by surface plasmon excitation

A theory is presented for the light-field enhancement (LFE) near a metal sphere when surface plasmons are excited. Both the spatial dispersion and electromagnetic retardation effects are shown to suppress the LFE if the sphere radius a becomes comparable with the screening length l_TF or the light wavelength λ, respectively. The maximum value of the LFE close to the result of quasi-electrostatics without spatial dispersion is achieved at a≈50 Å, in which case l_TFaλ/2π.     

Enhanced optical absorption for photovoltaics via excitation of waveguide and plasmon-polariton modes

We study theoretically the mechanisms by which optical absorption is enhanced in an optical nanostructure consisting of a slab waveguide, made of a-Si:H, sandwiched between a periodic array of metallic nanowires and a substrate, both made of Au. We demonstrate that for the TM polarization the optical absorption in the slab waveguide can be enhanced by almost an order of magnitude by the excitation of plasmon modes, whereas for both the TM and TE polarizations the grating-induced excitation of slab waveguide modes leads to more than twofold enhancement of the optical absorption.     

Fine frequency tuning in sum-frequency generation of continuous-wave single-frequency coherent light at 252 nm with dual-wavelength enhancement

Fine frequency tuning of the deep-ultraviolet single-mode coherent light at 252 nm was conducted through the PID feedback system automatically by changing the temperature of a beta-BaB(2)O(4) (BBO) crystal in a doubly resonant external cavity for the sum-frequency mixing of 373 and 780 nm light. The temperature-dependent frequency tuning rate is 19.3 MHzK(-1), which is sufficiently fine to realize the laser cooling of neutral silicon atoms because the natural width of the laser cooling transition is 28.8 MHz.     

Studies of interfacial regions by sum-frequency generation with a free-electron laser

The use of a Free-Electron Laser (FEL) allows the study of (non)linear optical properties of materials over unsurpassed large spectral intervals. As an example, we report on the use of a FEL as the infrared source in spectroscopic infrared-visible Sum-Frequency Generation (SFG). Employing the extremely wide tunability of the Free-Electron Laser for Infrared eXperiments (FELIX) at Rijnhuizen, we have studied the frequency dependence of the nonlinear susceptibility for sumfrequency generation in gallium phosphide between 20 and 32 m in great detail. We have developed a shortpulse visible laser system that is highly synchronous with FELIX thereby creating a two-color setup that can be broadly applied. Resonantly enhanced SFG in alphaquartz has been used to study the relative timing stability of FELIX and the synchronized picosecond-laser system.Paper presented at the 129th WE-Hearaeus-Seminar on Surface studies by Nonlinear Laser Spectroscopies, Kassel, Germany, May 30 to June 1, 1994     

On the origin of nonclassical light generation upon resonant excitation of a GaAs semiconductor microcavity

It was shown in JETP Lett. 102, 508 (2015) that the intensity correlation function of the emission from a high-quality-factor semiconductor microcavity under resonant optical pumping exhibits an oscillatory behavior with an unexpectedly long oscillation period and a long decay time, which fall in the nanosecond range. A further investigation demonstrates that the origin of these oscillations is not related to the weak Rabi interaction between long-lived localized exciton states in the quantum well and the electromagnetic field of the microcavity mode. It proves that the semiconductor microcavity plays a secondary role in the observation of nonclassical light: it provides the spectral selection of the modes of the pump laser. We believe that intrinsic instabilities lead to the chaotic excitation of spiking in the laser modes under a constant operating current.     

局域表面等离激元诱导的三次谐波增强效应

本文研究了二维金三角形纳米颗粒阵列的三次谐波非线性光学效应. 金三 角纳米颗粒阵列是基于微球刻印技术制成. 采用反射式光学系统, 观察到该纳米结构在光谱分辨的飞秒激光照射下产生明显的三次谐波. 研究表明, 当激光抽运频率接近金纳米颗粒的局域表面等离激元共振位置时, 三次谐波信号得到增强; 三次谐波辐射方向满足动量匹配条件. 关键词： 微球刻印 三次谐波产生 表面等离激元     

Optical modulation of surface plasmon-polariton coupling in a gallium/aluminium composite

We report on the use of a reversible nanoscale light-induced structural transformation in a new type of gallium/aluminium composite material interfaced with a dielectric to control the efficiency with which light is coupled to a surface plasmon-polariton wave at the interface, and thereby to modulate the optical reflectivity of the interface. An optical fluence of just a few mJ/cm² is sufficient to significantly modulate the composite’s dielectric properties and thus to provide high-contrast nonlinear optical and plasmonic switching functionality on a nano- to microsecond timescale, for signals in the visible and near infrared wavelength ranges.     

Features of spectral compression based on sum-frequency generation

Peculiarities of the process of spectral compression through sum-frequency generation are discussed for the case when nonlinear-dispersive similariton generated from a part of the signal is used as a reference pulse. The compression efficiency depending on the initial pulse intensity is studied. The possibility of spectral compression is discussed in the absence of self-phase modulation, when the reference and signal pulses have the same durations and spectral bandwidths.     

双轴晶体和频效应的相位匹配拓朴分析

根据非中心对称双轴晶体中两束基频光与它们产生的二次谐波的折射率曲面的关系及相位匹配条件,分析了和频效应相位匹配曲面的特点,对正常双轴晶体得出了可实现的29种相位匹配曲面拓扑图和存在条件,15种非临界相位匹配类型、存在条件和偏振关系.并用这种理论分析了LAP晶体、KB_5晶体的和频性能.     

Design of specific gratings operating under surface plasmon-polariton resonance

We present a productive method of designing specific diffraction gratings that ensure some predetermined energy redistributions between outgoing waves. It is based on the analytical solution of the direct and reverse diffraction problems under surface plasmon-polariton resonance and is supported by strict numerical calculations.