Chiral photonic crystals with an anisotropic defect layer: Oblique incidence

In the present paper we consider some properties of defect modes in chiral photonic crystals with an anisotropic defect layer at oblique light incidence. The problem is solved by Ambartsumian’s layer addition method. We investigated some peculiarities of the discussed system’s reflection spectra of the oblique light incidence for both the minimum and essential influences of the dielectric boundaries. Then we investigated some particulars of the density of photonic states spectra. We also discussed some peculiarities of the light energy distribution in the system. We found out that at large incidence angles two defect modes arise in the two regions of the selective reflection, each in one respectively, meanwhile, none arises in the central region of the complete reflection. Our investigations show that it is possible to rather widely change the emission peak wavelength in the subject system doped with some laser dye, by changing the incidence angle.     

REFLECTION OF ELECTROMAGNETIC WAVES FROM METALLIC MULTILAYERS

The reflection of electromagnetic waves on metallic multilayers is studied in terms of a hydrodynamical model .It is shown that for TE waves, selective reflections occur at frequencies ω>ω_pl in the case of vertical incidence and at higher frequencies in cases of oblique incidence, while for TM waves,they are totally reflected at all frequencies higher than ω_pl. These properties may render metallic multilayers useful in optical devices.     

体积全息图中光子禁带结构性质的分析

利用光子晶体的概念和方法，从理论上分析了一维全息图在再现光以不同角度入射情况下禁带结构的性质。分析表明，当再现光非正入射时，体积全息图的禁带结构是倾斜的，正入射时的非倾斜结构是倾斜结构的一个特例。     

Ultrathin atomic vapor film transmission spectroscopy: analysis of Dicke narrowing structure

Transmission sub-Doppler spectroscopy with confined atomic vapor film between two dielectric walls is theoretically studied. Because of atoms flying from wall to wall, where they get de-excited, the atomfield interaction time is anisotropic so that the contribution of slow atoms is enhanced, a sub-Doppler transmission spectroscopy (Dicke narrowing effect) can be obtained when the thickness of the film is much small or comparable with the wavelength even at small angle oblique incidence. It is feasible to get a sub-Doppler structure in a new region (L ＜λ/4) in experiments.     

Frequency Selective Characteristics of Dielectric Periodic Structures for Millimeter Wave Application

In this paper, the frequency selective reflection characteristics of dielectric periodic structures for the oblique incidence of a plane wave are analyzed by a method which combines the multimode network theory with the rigorous mode matching method. The variations of the total reflection characteristics with the geometric dimensions of the dielectric periodic structures are systematically investigated to develop useful guidelines for the design of the dielectric frequency selective surface. Moreover, the relationship between the related wave phenomenon and the dispersion characteristics of multilayer plane dielectric structure is explained with the theory of plane dielectric waveguide.     

Scattering Characteristics of Dielectric Periodic Structure Composed of Left-handed Materials with Arbitrary Oblique Incidence

Scattering characteristics of monolayer and multilayer dielectric periodic structure composed of left-handed materials (LH-DPS) with plane wave arbitrary oblique incidence are carefully analyzed using a method which combines multimode network theory with the rigorous mode matching method. Our analysis results reveal that the arbitrary oblique incident angles and relative position between different LH-DPS have great effects to the scattering characteristics of LH-DPS which different from the situation of dielectric periodic structure composed of right-handed materials (RH-DPS). The reasons why the reflection characteristics of the LH-DPS are totally different from those of the RH-DPS with arbitrary oblique incidence are also given. The present quantitive investigation provides guidelines for the design of the monolayer and multilayer dielectric frequency selective surfaces for millimeter wave applications.     

Study of the CdS crystal evaporation kinetics by laser step atomic photoionization

Laser resonant multistep atomic photoionization is employed to measure evaporation rates and saturated vapor pressures of cadmium sulfide and pure cadmium in temperature ranges of 585–950 and 350–535 K, respectively. It is shown that CdS thermally dissociates into Cd atoms and S₂ molecules. The photoionization of cadmium atoms follows the scheme

$5s^1 S_0 \xrightarrow{{\lambda _1 = 326.1nm}}5p^3 P_1 \xrightarrow{{\lambda _2 = 479.9nm}}6s^3 S_1 \xrightarrow{{\lambda _3 = 488.1nm}}17p^3 P_2 + (\varepsilon = 12kV/cm) \to Cd^ + + e^ - .$

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The minimal pressure of pure cadmium is found to be 10^?11 mm Hg.     

Electrical, optical, and photoelectric properties of electron-irradiated indium-doped cadmium sulfide single crystals

The effect of irradiation by 1.2-MeV electrons to a dose Φ=2×10¹⁷ cm^?2 on the electrical, optical, and photoelectric properties of In-doped CdS single crystals was studied. The experimental data obtained permit one to conclude that irradiation initiates decomposition of the supersaturated In solution in CdS, with the indium atoms at the sites of the cation sublattice being expelled by cadmium interstitial atoms. New slow-recombination centers were observed to exist in the irradiated CdS: In samples, with the maxima of optical quenching of the photoconductivity lying in the region of $\lambda _{M_1 } = 0.75\mu m$ and $\lambda _{M_2 } = 1.03\mu m$ . It is suggested that the new recombination centers are related to complexes containing cadmium vacancies and indium atoms.     

Peculiarities of Acoustic Wave Reflection from a Boundary or Layer of a Two-Phase Medium

A mathematical model is presented for determining the oblique incidence of an acoustic wave at both a boundary and layer of a gas–drop mixture or a bubbly liquid of finite thickness. The basic wave reflection and transmission patterns are established for the incidence of a low-frequency acoustic wave at an interface between a pure gas and a gas–drop mixture, as well as between a pure and bubbly liquid. A range of varying volume fractions for a drop is determined, for which the zero value of the reflection coefficient is possible for low frequencies at oblique incidence. It is shown that the reflection coefficient will never be zero at angles of incidence above 24.5° from a gas–drop mixture at a pure gas boundary; however, when a wave is incident from a pure gas at a gas–drop mixture boundary, a zero reflection coefficient is possible for nonzero angles of incidence and the volume fraction of inclusions. The results of calculating reflection of an acoustic wave from a two-phase layer of a medium with a finite thickness are presented. It is established that the minimum reflection coefficient is possible depending on the perturbation frequency for a certain range of angles of incidence for the boundary or the layer of the gas–drop mixture, which is governed mainly by difference in densities between it and the pure gas.     

Quantum thermal field fluctuation induced corrections to the interaction between two ground-state atoms

We generalize the formalism proposed by Dalibard, Dupont-Roc, and Cohen-Tannoudji (the DDC formalism) in the fourth order for two atoms in interaction with scalar fields in vacuum to a thermal bath at finite temperature T, and then calculate the interatomic interaction energy of two ground-state atoms separately in terms of the contributions of thermal fluctuations and the radiation reaction of the atoms and analyze in detail the thermal corrections to the van der Waals and Casimir–Polder interactions. We discover a particular region, i.e. $\sqrt[4]{{\lambda }^{3}\beta }\ll L\ll \lambda $ with L, β and λ denoting the interatomic separation, the wavelength of thermal photons and the transition wavelength of the atoms respectively, where the thermal corrections remarkably render the van der Waals force, which is usually attractive, repulsive, leading to an interesting crossover phenomenon of the interatomic interaction from attractive to repulsive as the temperature increases. We also find that the thermal corrections cause significant changes to the Casimir–Polder force when the temperature is sufficiently high, resulting in an attractive force proportional to TL⁻³ in the λ ≪ β ≪ L region, and a force that can be either attractive or repulsive and even vanishing in the β ≪ λ ≪ L region depending on the interatomic separation.     

双缀饰选择反射光谱的研究

研究了薄原子蒸气中Y型四能级系统的双缀饰选择反射光谱(DSR),其线型是三条色散曲线的叠加,其中两条反常色散线型对应于双缀饰电磁感应透明(DEIT).与单光子选择反射光谱(SR）相似,DSR也具有明显的Dicke窄化现象.由于暗态超慢原子的贡献和原子跃迁的量子相干效应,从DSR光谱可观察到显著的群速变慢效应.     

Absorptive reduction and width narrowing in Λ-type atoms confined between two dielectric walls

This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency （EIT） in a thin vapour film of A-type atoms confined between two dielectric walls whose thickness is comparable with the wavelength of the probe field. The absorptive lines of the weak probe field exhibit strong reductions and very narrow EIT dips, which mainly results from the velocity slow-down effects and transient behaviour of atoms in a confined system. It is also shown that the lines are modified by the strength of the coupling field and the ratio of L/λ, with L the film thickness and λthe wavelength of the probe field. A simple robust recipe for EIT in a thin medium is achievable in experiment.     

The effect of surface channeling of neutral atoms

Special features of reflection of neutral atoms from crystal surfaces are considered in the case of grazing incidence. It is shown that polarization effects and the long-range part of the potential of interaction of ions with atomic chains and planes can play an important role in describing processes of reflection of atoms from the surface. The analysis in this paper shows that the polarization of accelerated neutral atoms in the case of grazing incidence on the surface can lead to the formation of bound surface states. The threshold condition for the angle of arrival of atoms at the plane at which the capture by such states is possible is obtained.     

斜入射分层线性各向异性等离子体电磁散射时域有限差分方法分析

提出了斜入射分层线性各向异性等离子体电磁散射的时域有限差分(FDTD)方法,通过将二维麦克斯韦方程等价地转换为一维麦克斯韦方程,避免了用二维时域有限差分方法分析该散射问题,极大地提高了计算效率.分析推导了TEz和TMz波斜入射线性分层各向异性等离子体电磁散射的FDTD方法,然后通过该方法计算不同入射角的各向异性等离子板的电磁波反射系数,并与其解析解进行比较,结果表明该方法的准确性和有效性.最后,将该算法应用于计算涂覆分层各向异性等离子体金属板在不同入射角下的反射系数,分析了不同入射角对反射系数的影响.     

A method of suppression of diffraction oscillations near the diffraction reflection region

Light propagation through the layer of a chiral photonic crystal with graded parameters of modulation is considered in the case of oblique incidence. The problem is solved by the Ambartsumian’s layer addition method. It is shown that under certain conditions it is possible to suppress the diffraction oscillations near the diffraction reflection region.     

TE-TE mode coupling at oblique incidence in a periodic dielectric waveguide

The characteristics of reflection of a TE mode into another TE mode in a planar dielectric waveguide with a sinusoidally modulated index are investigated for the general case in which the wavevectors are not aligned with the grating vector. A singular perturbation procedure is used to deduce the asymptotically exact coupled mode equations which govern the interaction. An analysis of the coupled-mode equations has shown the existence of the Brewster phenomenon at the angle of incidence θ_iB=45°. For angles of incidence sufficiently greater than the Brewster angle, the reflection coefficient can be considerably larger than that for the normal incidence. In the spectral response curves of the reflection coefficient, a higher maximum and a smaller base bandwidth are possible for the oblique incidence as compared to that for the normal incidence. The angular sensitivity of the reflection characteristics increases as the angle of incidence changes from the normal incidence to the grazing incidence.     

薄原子蒸气的双光子Dicke窄化选择反射光谱

研究了囚禁于两电介质面间的(A)型三能级原子的双光子Dicke窄化选择反射(TDNSR)光谱.通过对不同膜厚及不同抽运光强度的TDNSR线璎的分析,发现由于蒸气中的原子与电介质表面碰撞的消激发效应和薄蒸气膜中的慢原子效应,以及双光子光谱的消多普勒配置,TDNSR线型在很多情形下表现为亚多普勒结构,且线型随 蒸气膜层的厚度与探测光波长的比值呈周期性变化.当L=2mλ/4(m为正整数)时,TDNSR消失.而当2mλ/4< L<(2m 2)A/4时.线型为典型的色散曲线,且L趋近(2m 1)λ/4时对称性增强.精确调谐强抽运光于能级|2>-|3>的跃迁时,在探测光的共振区域△d=0附近,TDNSR极高的变化率表明探测光具有显著的群速变慢效应.     

Selective Reflection of Laser Radiation from Ultrathin Layers of Cesium Atomic Vapors Confined in a Nanocell

The effect of the van der Waals interaction of cesium atoms with the sapphire windows of a nanocell was experimentally investigated using the selective reflection process. The distance L between the windows varied in the range of 50–2000 nm and the nanocell was filled with the vapors of cesium atoms. For the Cs atoms (the transition 6S_1/2 → 6P_1/2), the C₃ coefficient of the van der Waals interaction with the sapphire windows of the nanocell is measured. It is shown that it is possible to determine the magnetic fields with the spatial resolution of 70 nm using the selective reflection spectrum and, consequently, both the homogeneous and highly gradient magnetic fields can be measured.     

Experimental Estimation of the Frequency-Dependent Reflection Coefficient of a Sound-Absorbing Material at Oblique Incidence

A method for experimentally determining the frequency-dependent reflection coefficient of a sound-absorbing material at oblique incidence is presented. The M-sequence method and a monopole source are used to measure pulse responses of melamine foam for different angles of incidence of an acoustic wave. Frequency dependencies of the reflection coefficient obtained at different angles of incidence are compared with that calculated theoretically using the Biot model and approximate inversion of the Fourier–Bessel integral.     

Effects of oblique incidence on terahertz responses of planar split-ring resonators

Effects of oblique incidence of terahertz waves on the response of planar split-ring resonators are investigated, both experimentally and by simulation. It is found that the incident angle dependent phase delay and coupling conditions of neighboring split-ring resonator(SRR) units play important roles and greatly change both the transmission and reflection spectra for the resonant feature of linear charge oscillations. Our results show that the SRR structure-supported magnetoelectric couplings at oblique excitation are trivial and can be ignored. A highly symmetric response is found in the cross-polarization effects, which may manifest the bianisotropic properties of the SRR system but this needs further study.