He-Zhou Wang

The transmission characteristics of surface plasmon polaritons in ring resonator

A two-dimensional nanoscale structure which consists of two metal-insulator-metal (MIM) waveguides coupled to each other by a ring resonator is designed. The transmission characteristics of surface plasmon polaritons are studied in this structure. There are several types of modes in the transmission spectrum. These modes exhibit red shift when the radius of the ring increases. The transmission properties of such structure are simulated by the Finite-Difference Time-Domain (FDTD) method, and the eignwavelengths of the ring resonator are calculated theoretically. Results obtained by the theory of the ring resonator are consistent with those from the FDTD simulations.

Three-dimensional photonic crystals fabricated by visible light holographic lithography

In this report, we present three-dimensional photonic crystals fabricated by a four-beam holographic lithography method using visible photoinduced polymerization. High-quality face-centered-cubic single crystals with a large range of polymeric matrix volume fraction were fabricated using optimal conditions obtained from computer simulations. Optical measurements of the crystals showing photonic band-gap-like behavior are presented for different polymeric matrix volume fractions.

High-speed full analytical holographic computations for true-life scenes.

We develop a novel method to generate hologram of three-dimensional (3D) textured triangle-mesh-model that is reconstructed from ordinary digital photos. This method allows analytically encoding the 3D model consisting of triangles. In contrast to other polygon based holographic computations, our full analytical method will free oneself from the numerical error that is in the angular spectrum due to the Whittaker-Shannon sampling. In order to saving the computation time, we employ the GPU platform that is remarkably superior to the CPUs. We have rendered a true-life scene with colored textures as the first demo by our homemade software. The holographic reconstructed scene possesses high performances in many aspects such as depth cues, surface textures, shadings, and occlusions, etc. The GPUs algorithm performs hundreds of times faster than those of CPU.

Narrow frequency and sharp angular defect mode in one-dimensional photonic crystals from a photonic heterostructure.

By combining two one-dimensional defective photonic crystals (PCs), we obtained a photonic heterostructure with narrow frequency and a sharp angular defect mode. The key to obtaining such a structure is to design the two sub-PCs to make the frequencies of their defect modes the same at one incident angle and different at all other incident angles. Filters designed on the basis of this heterostructure possess not only a narrow-frequency passband but also a sharp angular pass breadth. Optimization of the practical design is also suggested.

Wideband slow light and dispersion control in oblique lattice photonic crystal waveguides

We find that the angle between elementary lattice vectors obviously affects the bandwidth and dispersion of slow light in photonic crystal line-defect waveguides. When the fluctuation of group index is strictly limited in a +/-1% range, the oblique lattice structures with the angle between elementary lattice vectors slightly larger than 60 degrees have broader available bandwidth of flat band slow light than triangular lattice structures. For example, for the angle 66 degrees , there are increases of the available bandwidth from 20% to 68% for several different structures. For the same angle and a +/-10% variation in group velocity, when group indices are nearly constants of 30, 48.5, 80 and 130, their corresponding bandwidths of flat band reach 20 nm, 11.8 nm, 7.3 nm and 3.9 nm around 1550 nm, respectively. The increasing of bandwidth is related to the shift of the anticrossing point towards smaller wave numbers.

A novel europium(III) complex with versatility in excitation ranging from infrared to ultraviolet

One- and two-photon absorption properties of a novel europium(III) complex containing a hemicyanine cation are investigated in this paper; in which the sensitization wavelength of europium(III), induced by beta-diketonate ligands, is in the ultraviolet range, and the hemicyanine(aminostyrylpyridinium) cation extends the sensitization wavelength of Eu(III) to visible region. Furthermore, under 1.06 microm ultrashort pulse laser excitation, the complex exhibits effective europium(III) luminescence induced by the two-photon absorption of the hemicyanine cation. Therefore, this new europium(III) complex with excitation bands in the near infrared, visible and ultraviolet ranges. Since the 1.06-microm ultrafast laser is one of the most frequently used laser sources and 1.06 microm is an optical window for cells and tissues, the results suggest that this kind of complex has promising applications in deep-penetrating and high quality bioimaging in vivo.

Crystallography of two-dimensional photonic lattices formed by holography of three noncoplanar beams

A systematically theoretical study on how to form two-dimensional photonic lattices with various plane groups by three elliptically polarized beams is presented. It is shown that nine plane groups can be formed in the photonic lattices by use of an intuitionistic intensity pattern-superposition method; however, we demonstrate that the other eight plane groups cannot be constructed. A phase shift associated with the interference intensity and the elliptic polarization is derived, and a relevant formula for interference intensity is deduced. The phase shift can be used to obtain the lower symmetries in some wallpaper groups such as p1, pm, cm, and p3m1 without introducing additional undesired symmetries. This analysis may lay the foundation for the study of space groups in holographic three-dimensional photonic crystals and multidimensional photonic quasicrystals.

Omnidirectional resonance modes in photonic crystal heterostructures containing single-negative materials

Multiple omnidirectional resonance modes are generated in the periodic arrangement of photonic crystal (PC) heterostructures with two sub-PCs consisting of single-negative (permittivity- or permeability-negative) materials. The key to designing such heterostructures is that only one of the sub-PCs possesses the zero-φeff gap. It is found that the resonance transmission modes inside the zero-φeff gap of these heterostructures are insensitive to incident angle. Moreover, as the periods of the heterostructure increases, the resonance transmission modes will split and be located symmetrical on both sides of the midfrequency of the zero-φeff gap.

Fraunhofer computer-generated hologram for diffused 3D scene in Fresnel region

A Fraunhofer computer-generated hologram (CGH) is proved to be valid in display for three-dimensional (3D) objects from the Fresnel to the far-field region without a Fourier lens for reconstruction. To quickly compute large and complicated 3D objects that consist of slanted diffused surfaces in the Fresnel region, a Fraunhofer-based analytical approach using a basic-triangle tiling diffuser is developed. Both theoretical and experimental results reveal that Fraunhofer CGH can perform the same effects as Fresnel CGH but require less calculation time. Impressive 3D solid effects are achieved in the Fresnel region.

Observation of Backscattering-Immune Chiral Electromagnetic Modes Without Time Reversal Breaking

A strategy is proposed to realize robust transport in a time reversal invariant photonic system. Using numerical simulation and a microwave experiment, we demonstrate that a chiral guided mode in the channel of a three-dimensional dielectric layer-by-layer photonic crystal is immune to the scattering of a square patch of metal or dielectric inserted to block the channel. The chirality based robust transport can be realized in nonmagnetic dielectric materials without any external field.