Green's tensors for photonic crystal (PC) slabs are numerically solved by the coupled-dipole approximation (CDA) technique. The obtained components of Green's tensors satisfy discontinuous or continuous conditions at interfaces of scatterers. This shows that the CDA technique is very applicable to studying the properties of PC slabs. Green's tensors exhibit obviously periodic oscillation with the increase of the number of scatterers; furthermore, the effect of each scatterer on Green's tensors displays a localization feature in the sample containing one row of scatterers; on the contrary, this localized effect disappears in the sample consisting of multiple rows of scatterers.

对非均匀电磁系统中原子的Lamb移位导出一个普适的理论公式，发现对Lamb移位的主要贡献来自实光子的吸收和再辐射过程，这打破了自1947年以来一直被人们所认同的传统概念，即在均匀空间中，Lamb移位主要来自虚光子的吸收和再辐射过程。对光子晶体，文章作者预言了巨Lamb移位效应。对原子集合，进一步发现依赖位置的Lamb移位将使一个能级扩展成一个能带，就像原子气体中依赖速度的多普勒效应一样。

Decay kinetic properties of a two-level atom near the band edges of photonic crystals (PCs) with absolute gaps are studied based on the Green's function expression for the evolution operator. The local coupling strength between the photons and an atom is evaluated by an exact numerical method. It is found that the decay behavior of an excited atom can be fundamentally changed by the variation of the atomic position: Weisskopf-Wigner and non-Weisskopf-Wigner decay phenomena occur at different atomic positions in the PCs as a result of a significant difference in the local coupling strength. Our finding implies that it is possible to engineer the luminescence spectrum by controlling the atomic position.

We present a general model study of surface-enhanced resonant Raman scattering and fluorescence focusing on the interplay between electromagnetic effects and the molecular dynamics. Our modelmolecule is placed close to two Ag nanoparticles, and has two electronic levels. A Franck-Condon mechanism provides electron-vibration coupling. Using realistic parameter values for the molecule we find that an electromagnetic enhancement by 10 orders of magnitude can yield Raman crosssections σR of the order 10−14 cm2. We also discuss the dependence of σR on incident laser intensity.

The lifetime distribution functions of the spontaneous emission (SE) of the excited atoms embedded in two-dimensional (2D) photonic crystals (PCs) with square lattice, consisting of square air rods in dielectric medium with different filling factors, are calculated by using the plane wave expansion method. The numerical results show that the SE in the 2D PCs cannot be prohibited completely but it can be inhibited intensively by the pseudo-PBG of the PCs. In the pseudoband edges, the SE is accelerated obviously. The reduced average lifetime of the excited atoms and the extension of the reduced lifetime distribution in the 2D PCs both are the same as those in the 3D PCs in the order of magnitude. Our results provide an available way to control the behavior of the SE by changing the structures of the 2D PCs.

We investigate the property of the localized mixed acoustic modes lying in the interior minigap in structural defect superlattices grown away from the cubic axis of bulk materials. It is found that the localized mixed modes always appear in pairs inside each interior minigap for certain structural parameters. Furthermore, there are degeneracy points between two branches of localized mixed modes. These characteristics are markedly different from localized folded acoustic phonon modes in minigaps that occur at the center and the edge of the Brillouin zone. We also find that the interior minigap and localized mixed modes strongly depend on the growth direction of the superlattices.

We investigate the property of the bound states with an infinite number of classical turning points in the semiconductor superlattices (SL's) with the double-barrier and double-well structural defects. The anomalous parity sequence of these bound states violating the conventional parity rule is predicted. A physical mechanism on the origin of the bound states in the structural defect SL's, different from the mechanism addressed in the previous literature, is proposed. Based upon it, the parity anomaly can be interpreted very well. In addition, we also study the property of the optical transition in this system, for instance, the evaluation of the optical transition probability from the bound states to the bound states, from the bound states to the delocalized scattering states, and from the scattering states to other scattering states, in detail.

The modulus of electric field eigenvector in photonic crystals (PCs), ｜En(k,r)｜, is confirmed to be variant for a set of k points in a k star, namely, ｜En(a[k],r)｜=｜En(k,r)｜, where $a% represents the operations of the lattice point group. Therefore, in the calculation of the local density of states (LDOS), all k points in the entire Brillioun zone should be included; otherwise, the results are generally incorrect. According to group theory, the transformation relation ｜En(a[k],r)｜=｜En(k,$aut%21r) ｜(heret represents the translation operator of the crystal, including the glide operation) is rigorously proven. This transformation can greatly save computing time spent in the diagonalization procedure of the eigenmode equation. Based upon this transform, a correct expression of calculating the LDOS is presented. This expression of the LDOS satisfies symmetry of the lattice. The detailed comparisons with the previous results based upon ｜En(a[k],r) ｜=｜En(k,r)｜ are given. The enhancement effects of the LDOS in the PCs with a fcc structure and a diamond structure, compared to the vacuum case, are revealed. It is found that the enhancement effect of the LDOS in the diamond structure is much larger than that in the fcc structure.

Spontaneous decay behavior from an assembly of atoms (or molecules) in a dielectric slab sandwiched by two dielectric semi-infinite spaces with arbitrary refractive indices is investigated. We introduce a lifetime distribution function to describe decay kinetics. The zero-point fluctuations of the electromagnetic field are calculated as a function of the position of atom in the slab. They display a symmetric profile with respect to the central plane of the slab in symmetric structure sample and the contributions of the guided modes and the radiation modes components both exhibit cosinelike variation with a base but with a phase difference of p. With the increase of the thickness of the slab, the oscillations become dense. In contrast, for the asymmetric structure case, the related curves are asymmetric with respect to the middle plane of slab and exhibit considerably distorted cosinelike oscillations. The dependence of the spontaneous emission rate of atoms on the thickness of the slab and the refractive indices of substrate also is surveyed. Our calculations show that quite wide or narrow lifetime distribution can occur for different thicknesses of the slab. The coexistence of both accelerated and inhibited decay processes appears. The calculated results are in good agreement with experimental results.

In this paper we present formulas for the transmission coefficient in multibarrier heterostructures when taking into account the space-dependent electron effective mass and the coupling between components of the motion of an electron in directions parallel and perpendicular to the interfaces. We find that the coupling leads to a decrease of the effective barrier height seen by the electron. The numerical calculations are carried out for the double-and triple-barrier heterostructures consisting of GaAs/Ga12xAlxAs. Our results show that the coupling effect leads not only significantly to a shift of resonant peaks toward the low-energy region, but also causes the broadening of resonant peaks and the reduction of the peak-to-valley ratio in the transmission spectrum. The coupling becomes more pronounced for higher-lying resonant states. In addition, the variation of the coupling strength with the concentration x of Al is also investigated.