Angular insensitive nonreciprocal ultrawide band absorption in plasma-embedded photonic crystals designed with improved particle swarm optimization algorithm

Using an improved particle swarm optimization algorithm(IPSO)to drive a transfer matrix method,a nonreciprocal absorber with an ultrawide absorption bandwidth and angular insensitivity is realized in plasma-embedded photonic crystals arranged in a structure composed of periodic and quasi-periodic sequences on a normalized scale.The effective dielectric function,which determines the absorption of the plasma,is subject to the basic parameters of the plasma,causing the absorption of the proposed absorber to be easily modulated by these parameters.Compared with other quasi-periodic sequences,the Octonacci sequence is superior both in relative bandwidth and absolute bandwidth.Under further optimization using IPSO with 14 parameters set to be optimized,the absorption characteristics of the proposed structure with different numbers of layers of the smallest structure unit N are shown and discussed.IPSO is also used to address angular insensitive nonreciprocal ultrawide bandwidth absorption,and the optimized result shows excellent unidirectional absorbability and angular insensitivity of the proposed structure.The impacts of the sequence number of quasi-periodic sequence M and collision frequency of plasma1ν1 to absorption in the angle domain and frequency domain are investigated.Additionally,the impedance match theory and the interference field theory are introduced to express the findings of the algorithm.

Synthesis, Structure of a Symmetrically Substituted Stilbene with Strong Two-photon Absorption and Up-converted Blue Fluorescence

Efficient Ti-catalyzed reductive coupling methodology was first employed to synthesize the symmetrical bis-donor stilbene, trans-4, 4'-bis[diphenyl amino] stilbene (BDPAS). X-ray diffraction analyses reveal that this new crystal belongs to the triclinic crystal system of centro-symmetric P-1 space group. The DBPAS solution, with the linear transmission at wavelength of greater than or equal to 450 nm, possesses large two-photon absorption cross section as high as 39.4x10(-48) cm(4).s/photon resulting in strong two-photon induced blue fluorescence of 460 nm, pumped by 740 nm laser irradiation.

Amplitude and phase controlled absorption and dispersion of coherently driven five-level atom in double-band photonic crystal

The absorption–dispersion properties of a microwave-driven five-level atom embedded in an isotropic photonic bandgap(PBG) have been studied. Due to the singular density of modes(DOM) in the isotropic PBG and the dynamically coherence induced by the coupling fields, modified reservoir-induced transparency and quantum interference-induced transparency emerge simultaneously. Their interaction leads to ultra-narrow spectral structure. As a result of closed-loop configuration, these features can be manipulated by the amplitudes and relative phase of the coherently driven fields. The position and width of PBG also have an influence on the spectra. The theoretical studies can provide us with more efficient methods to control the atomic absorption–dispersion properties, which have applications in optical switching and slow light.

General formula for phonon-assisted n-photon absorption in solids

A general formula for phonon-assisted n-photon absorption in solids is obtained by （n ＋ 1）-th order perturbation technique. The complicated calculation process for transition element of n-photon absorption is simply demonstrated by a diagram approach that is proposed in this work. We find that the transition element for the n-photon absorption has a simple form, i.e., it is just the first term of the n-th order fist kind Bessel function.

Observation of photon recoil effects in single-beam absorption spectroscopy with an ultracold strontium gas

We report on observing photon recoil effects in the absorption of a single monochromatic light at 689 nm through an ultracold ^(88)Sr gas,where the recoil frequency is comparable to natural linewidth of the narrow-line transition 5s^(2) ^(1)S_(0)-5s5p ^(3)P_(1) in strontium.In the regime of high-saturation,the absorption profile becomes asymmetric due to the photon-recoil shift,which is of the same order as the natural linewidth.The lineshape is described by an extension of the optical Bloch equations including the momentum transfers to atoms during emission and absorption of photons.Our work reveals the photon recoil effects in a simplest single-beam absorption setting,which is of significant relevance to other applications such as saturation spectroscopy,Ramsey interferometry,and absorption imaging.

Triple and Double Photons Absorption Process and Down-Conversion Laser Emitting Investigation of Er-Ion Doped Microsphere

We report a readily and cheap method to build taper optical fiber-Er3+ doped microsphere platform to investigate upconversion fluorescence emission and down-conversion laser oscillation with low threshold pump power. We demonstrate to dope Er3+ into silica microsphere surface by dipping a single-taper optical fiber into a certain concentration of erbium nitrate solution (Er(NO3)) , then dry it and use the electrical-arc of the optical fiber splicer to melt the tip of taper fiber to form the Er3+-doped silica microsphere due to surface tension induced. We also present a HF acid etching setup to fabricate low loss biconical optical taper fibers. We demonstrate the Er3+ doped silica microsphere triple photons and dual photons absorption process of up-conversion fluorescence emission and down-conversion laser oscillation spectra by using the optical tapered fiber to couple 976 nm/1534 nm pump light source.

Effects of Vacuum-Induced Coherence on One- and Two-Photon Absorption Spectra of Transient Process in a Y-Type System

我们在一个上调查导致真空的连贯的影响 -- 在一个四水平的 Y 类型原子系统的短暂进程的 andtwo 光子吸收。我们发现一个光子和二光子的短暂吸收和扩大性质对导致 thevacuum 的连贯相当敏感。一个光子和短暂过程的二光子的吸收系列能被 modulating 戏剧性地影响，这也被显示出应用领域的相对阶段。由适当地选择相对阶段，探查地的扩大能被完成。

One- and two-photon absorption-amplification response in a four-level atomic system with vacuum-induced coherence

This paper theoretically studies the effects of the vacuum-induced coherence on one- and two-photon absorption in a four-level atomic medium. It finds that the one- and two-photon absorption and amplification properties are quite sensitive to the vacuum-induced coherence. It is also shown that the one- and two-photon absorption spectra can be dramatically affected by modulating the relative phase of the applied fields, With the proper choice of the relative phase, the amplification without inversion for the probe field can be realized.

Two-photon Absorption and Optical Power Limiting Properties of Two Novel Dibenzothiophene-based Chromophores

Two novel V-shaped symmetric chromophores： E-2,8-bis（4-vinyl-4-carbazol-9-yl）diben- zothiophene （abbreviated as SK-G1） and E-2,8-bis（4-vinyl-4-triphenylamino） dibenzothiophene （abbreviated as ST-G1） have been synthesized and characterized. Their two photon absorption properties were measured by the open-aperture femtosecond Z-scan technique and the nanosecond nonlinear optical transmission （NLT）, respectively, when pumped by Ti： sapphire laser at 750 nm and 800 nm.

Theoretical studies on the one-and two-photon absorption properties of azulenylporphyrins and azulene-fused porphyrins

The electronic structures, one-photon absorption （OPA） and two-photon absorption （TPA） properties of the azulenylporphyrins and azulene-fused porphyrins have been comparatively studied by using DFT/B3LYP/6-31G（d） and the ZINDO/SDCI method. With the number of azulenyl groups increasing, the OPA wavelengths of all molecules are red-shifted in 400-600 nm and the two-photon absorption cross section is gradually enlarged. The azulene-fused structures facilitate an expanding conjugated area and increasing TPA cross section. The origin of TPA properties of studied compounds is studied with a two-level model. In summary, the azulene-fused porphyrins exhibit strong two-photon absorption.

Novel triphenylamine-based two-photon absorption dyes including benzophenone parts

New two-photon absorption dyes including benzophenone parts, p-N,N-diphenylamino-p＇-phenacylstilbene （C1）, 4,4-di-（4- benzoylstyrene）yltriphenylamine （C2） and 4,4＇,4＇-tri（4-benzoylstyrene）yltriphenylamine （C3）, were synthesized and characterized by ^1H NMR and elemental analysis. The ratio of the molar extinction coefficients of compounds was approximately equal to the ratio of the branch amount of the compounds, namely, C1：C2：C3 was 1：2：3. Extremely high fluorescence quantum yields were detected for these compounds. These molecules exhibited obvious two-photon upconcerted fluorescence as excited by 800 nm Ti：sapphire femtosecond laser.

Direct Calculation of Two-Photon Absorption Transition Intensities of Pr ^(3+) in Cs_2NaPrCl_6

Sixteen two-photon absorption (TPA) transition line strengths were calculated for the Pr 3+ ion in the cubic host Cs_2NaPrCl_6. In the calculation, two kinds of intermediate virtual excited (4f5d) states were utilized, one was the direct product of 4f1 core and 5d1 electronic states, and the other was 4f5d coupled states obtained by using the Reid f2 and fd programs. It was found that the calculated trends in intensities are fairly similar and the interaction between the 5d electron and the (4f)1 core in the 4f5d configuration does not provide dominant contributions to the two-photon absorption transition intensity of the Pr 3+ ion. In addition, the main channels of the strongest two-photon transition 3H_4Γ_1→3P_2Γ_5 were also obtained.

Controllable Absorption and Dispersion Properties of an RF-driven Five-Level Atom in a Double-Band Photonic-Band-Gap Material

驾驶五水平的原子在 photonic 晶体嵌入的无线电频率(RF ) 的探查吸收分散系列被考虑各向同性的双乐队 photonic-band-gap (PBG ) 水库调查。在使用的模型，分别地，二转变被上面、更低的乐队在如此的 PBG 材料联合，因此导致一些好奇的现象。数字模拟为光系列被执行。当一转变频率在乐队差距内，其它在差距外面时，它被发现那，在那里出现在吸收系列的三座山峰。然而，为案例，二转变频率躺着在内或在乐队差距外面，系列显示四吸收侧面。特别，在那里出现在系列的二座锋利的山峰当两转变频率在乐队内存在时，豁开。吸收性、散的反应上的驾驶 RF 的地的紧张和频率的影响在不同乐队边位置下面被分析。一个透明性窗口出现在吸收系列，这被发现并且被调整系统参数被分散侧面的一个很陡峭的变化伴随。这些结果证明系统的吸收分散性质强烈取决于导致 RF 的量干扰和 PBG 水库的状态(DOS ) 的密度。

Protonation Effect on One- and Two-photon Absorption Property of a Newly Synthesized Octupolar Chromophore

一个光子和有 1,3,5-triazine 核心和吡咯的 octupolar 分子 TA 的二光子的吸收性质上的 protonation 效果捐赠电子的结束组在混合密度被学习了功能的理论水平。一个计算计划被开发模仿纳入一个原子的一个质子。当混合物被转变从时，数字结果证明在一个光子和二光子的吸收性质的大变化被观察对三方面的 protonated 状态中立。当混合物是 protonated 时，更多的费用转移状态出现并且吸收乐队一红移动。而且，二光子的吸收剖面图大部分被提高。理论计算在支持 intramolecular 费用转移力量上表明 protonation 效果。结果与试验性的观察介绍质的同意。有复合 TA 的一个二光子的吸收开关基于 protonation 效果被建议。

Inhibition of Two-Photon Absorption in a Four-Level Atomic System with Closed-Loop Configuration

我们理论上与靠近环的配置在 acoherently 驾驶的四水平的原子系统调查二光子的吸收的特征。它被发现 thattwo 光子吸收能就被适当地调整四个协调低紧张的开车领域的相对阶段完全压制，原子系统成为透明 againsttwo 光子吸收。从一个物理观点，我们 exphcitly 以由二条不同二光子的刺激隧道导致的量干扰解释这些结果。

Spectroscopic Properties and Three-photon Absorption Induced Optical Limiting of Series of Novel Nonlinear Chromophores

有对称的 D 的三新奇非线性的色基 -- D 分子的结构和扩大结合的长度被综合。Solvatochromism 分析显示出在在地面和激动的状态之间的偶极子时刻由改进发生在色基的大对称的 intramolecular 充电转移。限制由三光子的吸收(3PA ) 导致了的光力量的性质被表明。大 3PA coeficients 和象 1074 cm6 s2 一样高的相应的分子的生气的节从非线性的传播大小在 1.06 m 为毫微秒激光脉搏被获得。

Enhancement of Two-photon Absorption by Ce^(3+) Sensitization in Organic Dyes

The two-photon absorption（TPA）and TPA-induced frequency upconversion emission properties of the dyes 4-[P-（dicyanoethylamino）crystal]-N-methypyrdinium iodide and the complex of 4-[P-（dicyanoethylamino）crystal]-N-methypyrdinium iodide and Ce（NO3）3 were experimentally studied.It was found that the TPA cross section for the dye sensitized by Ce3＋ is two factors larger than that of the dye without being sensitized.A three-level system model of the dye molecules was used to analyze the enhancement of TPA by the sensitizer Ce3＋,which indicated that the sensitizer results in the increase of the transition dipole moment from the one-photon allowed excited state（1Bu）to the two-photon allowed excited state（2Ag）.

Isomerism and coordination mode effects on two-photon absorption of tris(picolyl)amine-based fluorescent probes for zinc ions

One-photon absorption and two-photon absorption（TPA） properties of three tris（picolyl）amine-based zinc ion sensors are investigated by employing the density functional response theory in combination with the polarizable continuum model.The different isomer and coordination geometry of each probe are taken into account. Special emphasis is placed on the effects of isomerism and the coordination mode on the optical properties. The intra-molecular charge transfer（ICT）properties are specified by natural bond orbital charge analysis. It is shown that the isomerism has non-negligible effects on TPA properties of free ligands. It is found that both the TPA wavelength and the cross section are highly dependent on the coordination mode. When the zinc ion connects with the picolyl unit in the middle of a ligand, the zinc complex has a large TPA intensity in a long wavelength range due to the increased ICT mechanism.

Variation of Two-photon Absorption Cross Sections and Optical Limiting of Compounds Induced by Static Electric Field

由数字地用一个反复的预言者修正者解决 Maxwell-Bloch 方程有限差别的时间域技术，我们调查在 4,4 二度(di-n-butylamino ) 宣传很少周期激光脉搏的性质芪(BDBAS ) 分子的媒介当一个静态的电场存在时。动态二光子的吸收(TPA ) 十字节被获得并且光限制(OL ) 行为被显示。结果证明当静态的电场紧张增加时，动态 TPA 生气的节被提高， OL 行为被改进。而且，平顺序、奇怪顺序的泛音光谱因为它打破 BDBAS 分子的倒置对称，部件与静态的电场的存在被产生。这个工作提供一个方法调制 BDBAS 混合物的非线性的光性质。