Shi-Yao Zhu

Omnidirectional gap and defect mode of one-dimensional photonic crystals containing negative-index materials

We show theoretically that a one-dimensional photonic crystal containing a negative-index material has an omnidirectional gap, owing to the mechanism of zero (volume) averaged refractive index. In contrast to the Bragg gap, the edge of such a zero-n gap is insensitive to incident angle and polarization. When an impurity is introduced, a defect mode appears inside the zero-n gap with a very weak dependence on incident angle and invariant with scaling.

Electronic band gaps and transport properties in graphene superlattices with one-dimensional periodic potentials of square barriers

The electronic transport properties and band structures for the graphene-based one-dimensional (1D) superlattices with periodic potentials of square barriers are investigated. It is found that a new Dirac point is formed, which is exactly located at the energy which corresponds to the zero (volume) averaged wave number inside the 1D periodic potentials. The location of such a new Dirac point is robust against variations in the lattice constant, and it is only dependent on the ratio of widths of the potential barriers. The zero-averaged wave-number gap associated with the new Dirac point is insensitive to both the lattice constant and the structural disorder and the defect mode in the zero-averaged wave-number gap is weakly dependent on the incident angles of carriers.

Large negative Goos-Hänchen shift from a weakly absorbing dielectric slab.

It is theoretically shown that the negative Goos-Hänchen shifts near resonance, Re[k(z)d] = m pi, can be an order of magnitude larger than the wavelength for both TE- and TM-polarized beams reflected from a weakly absorbing dielectric slab if the absorption of the slab is sufficiently weak, which is different from the case for a lossless dielectric slab [Phys. Rev. Lett. 91, 133903 (2003)].

Giant lateral shift of a light beam at the defect mode in one-dimensional photonic crystals

It is found that when a light beam is incident on a one-dimensional photonic crystal (1DPC) containing a defect layer, the lateral shifts of both the reflected and the transmitted beams are greatly enhanced near the defect mode of the 1DPC, whose location depends on the angles at a fixed frequency. The effect was studied by use of a Gaussian beam. The giant lateral displacement is due to the localization of the electromagnetic wave.

Tunneling modes of photonic heterostructures consisting of single-negative materials

We show theoretically that heterostructures consisting of single-negative materials can possess tunneling modes inside forbidden gaps, owing to the resonant coupling of the evanescent-wave-based interface modes. The tunneling modes appear when the heterostructure becomes nihility. They are independent of incident angles and polarizations and have zero phase delay, which can be utilized to design zero-phase-shift omnidirectional filters.

Ultra-large index of refraction via quantum interference

Abstract Atoms prepared in a coherent superposition of an excited state doublet by a strong driving field can produce a large resonant index of refraction with vanishing absorption.

Precision localization of single atom using Autler–Townes microscopy

Abstract Detuning of the classical standing wave field with the atomic transition plays an important role in the characterization of the peaks present in Autler–Townes spontaneous spectrum of a three-level atom. We investigate how this detuning effects the position distribution of the atom and show that we gain a precision in position information of the single atom inside the standing wave field by introducing the detuning between the atomic transition frequency and the frequency of the driving field in the upper-level coupling case. We also show that this precision in localization of an atom is not observed in the lower-level coupling case, due to the absence of the quantum interference.

Partially coherent light pulse and its propagation

The concept of partially coherent Gaussian Schell-Model pulse (GSMP) is introduced in time domain, which can be used to characterize light pulses whose amplitude and phase are partially correlated. An analytical propagation formula of GSMP through dispersive media is derived rigorously by using tensor method. An application example showing the influences of coherence property on the propagation of pulses are illustrated.

Time delay of light propagation through defect modes of one-dimensional photonic band-gap structures

Light propagation through one-dimensional photonic band-gap structures with defect layers embedded at the center was investigated. The localization of the defect mode results in a great delay of propagation time. The average time spent in each layer is given. From the temporal behavior we can deduce the energy distribution in the interior of the photonic band-gap structure and calculate the average velocity of light propagation. The average velocity depends sensitively on the number of layers and the contrast of the refractive indexes.

Large negative lateral shifts from the Kretschmann–Raether configuration with left-handed materials

A large negative lateral shift of a light beam reflected from the so-called Kretschmann–Raether configuration containing left-handed material is predicted due to the formation of the unusual standing wave. An analytical resonant condition is given when there is a large negative lateral shift.