Nonlinear surface plasmon polaritonic crystals

We present an overview of the optical properties of nonlinear surface plasmon polaritonic crystals and their applications to control light with light. Surface plasmon polaritonic crystals are periodically nanostructured metal surfaces or thin metal films that act as two‐dimensional photonic crystals for surface polaritons. Hybritization of such nanostructures with dielectrics exhibiting an optical nonlinear response allows utilization of the electromagnetic field enhancement effects to observe nonlinear effects and bistable behaviour at low light intensities. By changing the geometry of the nanostructured film, the dispersion of the crystal is modified and, thus, electromagnetic mode structure and associated density of states can be controllably tuned in the desired spectral range. This provides enhanced flexibility in engineering the nonlinear optical response of plasmonic crystals in a chosen spectral range for both control and signal wavelengths.     

Surface-plasmon-polariton-induced suppressed transmission through ultrathin metal disk arrays

We report surface-plasmon-polariton-induced suppressed transmission through two-dimensional arrays of isolated metal disks with a thickness comparable to optical skin depth of the metal. A transmittance dip of -17.5 dB is achieved at the resonant wavelength of 1524 nm, compared to -12 dB for closed film. Coupling the light into the surface-plasmon polariton results in enhanced absorption, which is potentially interesting in solar cell applications.     

Dual-wavelength, two-crystal, continuous-wave optical parametric oscillator

We report a cw optical parametric oscillator (OPO) in a novel architecture comprising two nonlinear crystals in a single cavity, providing two independently tunable pairs of signal and idler wavelengths. Based on a singly resonant oscillator design, the device permits access to arbitrary signal and idler wavelength combinations within the parametric gain bandwidth and reflectivity of the OPO cavity mirrors. Using two identical 30 mm long MgO:sPPLT crystals in a compact four-mirror ring resonator pumped at 532 nm, we generate two pairs of signal and idler wavelengths with arbitrary tuning across 850-1430 nm, and demonstrate a frequency separation in the resonant signal waves down to 0.55 THz. Moreover, near wavelength-matched condition, coherent energy coupling between the resonant signal waves, results in reduced operation threshold and increased output power. A total output power >2.8 W with peak-to-peak power stability of 16% over 2 h is obtained.     

The effect of absorption on light filtering in randomly layered dielectric systems

Abstract

We study the effect of absorption on the transmission of light in a system of randomly distributed dielectric layers having identical optical length. In such systems, resonant transmission peaks have been obtained at wavelengths corresponding to multiples of the optical length. The absorption is found to leave the width of these peaks almost unaffected, while it substantially reduces the intensity of the transmitted light. Thus the high resolution is not destroyed by absorption, so this device remains a good potential candidate for use in light filtering compared to existing filters.     

Selective stop-band switching in two-dimensional multicomponent photonic crystals

A comprehensive theoretical investigation of the stop-band switching in two-dimensional multicomponent photonic crystals is carried out. The calculations are performed within the analytical model based on analysis of the scattering form-factor. Earlier, this approach was used to describe experimental data obtained in a study of synthetic opals representing three-dimensional photonic crystals. We report here on the development of a new version of this model applicable to the class of two-dimensional photonic crystals. The existence of resonant (non-switchable) stop-bands and the possibility of selectively controlling light flows propagating at different wavelengths is predicted. These effects draw up new guidelines for the design of two-dimensional photonic crystals possessing desired optical qualities.     

Resonant behavior and selective switching of stop bands in three-dimensional photonic crystals with inhomogeneous components

We demonstrate that, in contrast with the well-studied photonic crystals consisting of two homogeneous components, photonic crystals comprised of inhomogeneous or multiple (three or more) components may bring new opportunities to photonics due to the discovered quasiperiodic resonant behavior of their (hkl) stop bands as a function of the reciprocal lattice vector. A resonant stop band cannot be switched off for any permittivity of structural components. Tuning the permittivity or structural parameters allows the selective on-off switching of nonresonant (hkl) stop bands. This independent manipulation of light at different Bragg wavelengths provides a new degree of freedom to design selective optical switches and waveguides. Transmission experiments performed on synthetic opals confirmed the theoretical predictions.     

基于环形微腔的多频段三角晶格光子晶体耦合腔波导光学传输特性

本文理论研究了近红外波段硅基三角晶格光子晶体环形微腔的光场局域特性,通过将微腔在空间周期性排列组成耦合腔光波导,研究了多个导带区域内光束传输时的群速度,最大和最小值分别为0.0028c和0.00028c.将环形微腔在垂直于光传输方向上进行交错排列,通过改变相邻微腔之间的耦合区域,可以大幅降低多频段范围内光束在耦合腔波导中传输时群速度之间的差异,并提高部分频段的透过率数值.在不改变介质柱半径条件下,通过去掉三角晶格光子晶体中距中心介质柱距离分别为2a和√3a的六个介质柱构成了两种微腔,研究了两种微腔所支持的谐振波长之间的差异,在此基础上构造了两种耦合腔波导,进而将这两种耦合腔光波导与W1型输入/输出波导相连,最终实现了在多个不同频率范围内降低群速度的同时实现频段选择和频段分束功能,其导模群速度可降低到0.00047c.     

Magnetoelectrically coupled polariton excitation in a plasmonic crystal composed of nanorod dimers

In this work, the long wavelength optical properties of a plasmonic crystal, composed of gold nanorod dimers arranged parallel, have been studied. Due to the strong coupling between incident light and the oscillation of free electrons inside nanorod dimers, the magnetically induced and/or magnetoelectrically coupled plasmonic polaritons can be excited. A theoretical demonstration has been proposed and coupled equations that show similar profiles to the Huang-Kun equations for ionic crystals have been deduced, indicating the constitutive abnormalities and polaritonic bandgap effect. The analogy between the magnetoelectrically coupled metamaterials and ionic crystals may shed light on physical explanations, as well as constitutive parameter retrieval, for the magnetoelectric metamaterials.     

Optical Anisotropy of Photonic Crystals of Cubic Symmetry Induced by Multiple Diffraction of Light

The optical spectra of Bragg reflection from opal-like photonic crystals under conditions of the resonant enhancement of the multiple diffraction of light have been studied experimentally and theoretically using the photonic crystal structures prepared of monodisperse polystyrene globules. It is shown that the reflection signal registered in mutually orthogonal configurations of the polarizer and analyzer is related to the intrinsic optical anisotropy of the crystals and is a specific manifestation of the multiple Bragg diffraction in three-dimensional photonic crystals.     

基于瞬态光栅频率分辨光学开关法测量飞秒脉冲的研究

超宽光谱的飞秒脉冲测量一直是超快激光领域的重要研究方向之一.常规的飞秒脉冲自相关方法是通过测量自相关倍频信号来获得,而倍频信号具有波长选择性,不同中心波长的飞秒脉冲测量需要更换不同的倍频晶体,十分不方便.因此,提出了一种改进型的瞬态光栅频率分辨光学开关(TG-FROG)方法用于测量飞秒脉冲.该方法结合四波混频和频率分辨光学开关方法,其基本过程是将待测脉冲分为三束,其中两束脉冲经过精密的延时控制并聚焦在光学介质上达到时空重合,利用三阶非线性效应产生稳定的瞬态光栅作为开关光;另一束脉冲作为探测光与产生的瞬态光栅进行相互作用产生一个信号光,使用光谱仪对该信号光的光谱与延迟时间进行测量,并通过反演迭代算法处理而获取待测飞秒脉冲的光谱与电场信息.该方法只需要待测光的功率密度达到三阶非线性效应就可以实现测量,因此可以应用于任意中心波长的飞秒脉冲测量.利用该方法对中心波长分别为800 nm, 400 nm的飞秒脉冲,以及超连续亚10 fs的周期量级超宽光谱飞秒脉冲进行了测量,并与常规的干涉自相关仪器测量结果进行了比较,所得测量结果基本一致.实验结果表明,建立的基于TG-FROG方法对不同中心波长,不同脉冲宽度的飞秒脉冲测量是十分有效的.     

All-optical switch based on photonic crystal microcavity with multi-resonant modes

We present a design of all-optical switches based on one-dimensional photonic crystals (1D PhC) doped with nonlinear optical materials. The 1D PhC switch structure is composed of a PhC cavity sandwiched by two accessional PhC microcavities. The center PhC cavity has two resonant frequencies with nearly the same quality factors (Q), while the accessional PhC cavities have the same resonant frequency, which is equal to one of the resonant frequencies of the center cavity. The two accessional PhC cavities cause reduction of Q value in this resonant frequency and result in different Q values of two modes. We realize all-optical switch effect by selecting pump light wavelength at the low Q mode and probe light wavelength at the other mode. The theoretical simulations by using the finite difference time domain method show that the pump light intensity required to realize optical switch effect in the designed switch is 50 times smaller than that in one-dimensional photonic crystals cavity with only one resonant mode.     

亚波长金属光栅的表面等离子体激元共振特性

亚波长金属光栅在共振波长处有光场局域增强、异常透射等现象,为深入认识其共振机制,本文研究了亚波长金属光栅的表面等离子体激元（SPP）共振特性。通过研究不同金属光栅的几何结构以及金属介电常数对SPP共振波长的影响,获得了3种共振波长的基本物理机制。采用周期边界元法进行数值模拟,在边界积分方程的基础上结合平面波展开方法来处理任意形状的周期性结构。模拟结果表明,3种共振波长可以分别由金属的材料、金属光栅周期和金属光栅厚度所调谐。该研究为微纳米光学器件的设计提供了依据。     

Tunable Fabry-Pérot filter based on one-dimensional photonic crystals with liquid crystal components

A theoretical study of a tunable Fabry-Pérot multilayer structure composed of alternating layers of silicon and liquid crystal is presented and analyzed. The structure possesses two resonant frequencies within the stop band with tunable wavelengths and transmission properties. Tuning is achieved by allowing different orientations of the liquid crystal optical axes within the cavity and within the mirrors, while keeping the optical axes parallel to the layers. Applying the transfer matrix method for thin layers of anisotropic materials we demonstrate that the resonant wavelengths depend on the difference between the liquid crystal optical axis orientations. Besides, we are able to obtain a complete characterization of the structure in the form of its Jones matrix. From this, we propose an optical two-channel equalizer for applications around 1.55 μm that allows tuning the two resonant wavelengths and their relative amplitude levels.     

Tunable,dual-wavelength interferometrically coupled continuous-wave parametric source

Generation of dual-wavelength continuous-wave (cw) radiation with independent and arbitrarily tuning, and indefinitely close spacing, using two cw optical parametric oscillators (OPOs) coupled with an anti-resonant ring interferometer is reported. The singly resonant OPOs, based on identical 30-mm-long MgO:sPPLT crystals, are pumped by a single cw laser at 532 nm. Two pairs of signal and idler wavelengths can be independently and arbitrarily tuned, with each signal (idler) pair tuned through degeneracy and beyond. Frequency separation between two distinct resonant signal waves from 7 down to 0.8 THz is demonstrated, and their overlap at 951 nm providing a frequency difference as small as ~220 MHz is shown. The OPOs independently provide a signal (idler) wavelength coverage across 870–1,000 nm (1,040–1,370 nm) and simultaneously generate idler powers of >1 W.     

Scattering properties of an individual metallic nano-spheroid by the incident polarized light wave

The scattering properties of a metallic nano-spheroid under the illumination of different polarized light waves are investigated using 3D boundary element method. The influences of different geometrical sizes of the nano-spheroid and incident directions of the illuminating light wave on the scattering spectrum are studied for different incident polarized light waves. The results show that the metallic nano-spheroid has two intrinsic resonant modes, corresponding to different polarization states and resonant wavelengths. The scattering enhancement, the resonant wavelength, and the location of the enhanced optical field are strongly dependent on the polarization properties of the illuminating light waves, and they can be modulated by appropriately choosing the polarization directions of the incident light wave.     

Manipulation of subwavelength optical fields and resonant field enhancements of a silver-shell nanocylinder pair and chain waveguides with different core–shell patterns

Near field optical properties and surface plasmon resonances on a pair of silver-shell nanocylinder and nanochain waveguides with different core–shell patterns which interact with incident plane wave along chain axis are numerically investigated by using the finite element method. Simulation results show that the peak wavelengths and resonant field enhancements are highly tunable by using the nanoshell particles instead of solid ones, revealing a critical relationship among the wavelengths and illuminated direction of incident light, interparticle spacing, radii, and medium of dielectric holes and the patterns of chain waveguides. Besides, nanochain waveguides with different patterns of core–shell that are operated on resonant multipolar modes can provide higher propagation intensities and the transmission ability can be increased by decreasing the size of nanocylinders along the chain axis.     

非谐振腔型KTP光参变振荡器

研究了双晶体走离补偿、非谐振腔型KTP光参变振荡器，利用一套膜片实现了KTP相位匹配所允许的全波段调谐，信号光调谐范围0.698μm-1.026μm，闲频光调谐范围1.105μm-2.237μm。5倍阈值处，信号光840nm最高输出能量53mJ，能量转换效率25.8%，量子转换效率40％，闲频光的量子郊率也达到32％。     

Magnetochiral anisotropy in Bragg scattering

We show experimentally that light scattering in cholesteric liquid crystals shows strongly resonant magnetochiral anisotropy near the Bragg resonance; the optical transmission of unpolarized light depends linearly on an external longitudinal magnetic field and on the handedness of the medium.     

Specific features of polarization anisotropy in optical reflection and transmission of colloidal photonic crystals

This paper reports on the measurements (in linearly polarized light) of the transmission and reflection spectra of colloidal photonic crystals with three-dimensional and one-two-dimensional photonic band structure, i.e., opal films and Langmuir-Blodgett crystals with a refractive index contrast of ∼1.5: 1.0. It has been shown that the polarization anisotropy is enhanced considerably in the diffraction resonance range both in transmitted and reflected light, and that the anisotropy in the resonance range can be as high as 99%. The interaction of photonic crystal eigenmodes has been found to affect the polarization anisotropy. The assumption has been made that the coincidence of the maxima in polarization anisotropy of the resonant and nonresonant light reflection in colloidal crystals originates from the disorder in their lattices. The generality of the results obtained is confirmed by the fact that the polarization anisotropy manifests itself in the same way in colloidal crystals with different lattice symmetries.