Nuo Ba

Function photonic crystals

Abstract In this paper, we present a new kind of function photonic crystals (PCs), whose refractive index is a function of space position. Conventional PCs structure grows from two materials, A and B, with different dielectric constants e A and e B . Based on Fermat principle, we give the motion equations of light in one-dimensional, two-dimensional and three-dimensional function photonic crystals. For one-dimensional function photonic crystals, we give the dispersion relation, band gap structure and transmissivity, and compare them with conventional photonic crystals, and we find the following: (1) For the vertical and non-vertical incidence light of function photonic crystals, there are band gap structures, and for only the vertical incidence light, the conventional PCs have band gap structures. (2) By choosing various refractive index distribution functions n(z), we can obtain more wider or more narrower band gap structure than conventional photonic crystals.

The effect of defect layer on transmissivity and light field distribution in general function photonic crystals

We have theoretically investigated a general function photonic crystals (GFPCs) with defect layer, and choose the line refractive index function for two mediums A and B, and analyze the effect of defect layers position, refractive indexes, period numbers and optical thickness on the transmission intensity and the electric field distribution. We obtain some new characters that are different from the conventional PCs, which should be helpful in the design of photonic crystals.

Light field distribution of general function photonic crystals

Abstract In this paper, We have presented a new general function photonic crystals (GFPCs), which refractive indexes are line functions of space position in two mediums A and B , and obtain new results. (1) When the line function of refractive indexes is up or down, the transmissivity can be far larger or smaller than 1. (2) When the refractive indexes function increase or decrease along the direction of incident light, the light intensity should be magnified or weaken, which can be made optical magnifier or attenuator. (3) The GFPCs can be made optical diode when the light positive and negative incident the GFPCs.

Transmission character of general function photonic crystals

Abstract In the paper, we present a new general function photonic crystals (GFPCs), whose refractive index of medium is a arbitrary function of space position. Unlike conventional photonic crystals (PCs), whose structure grows from two mediums A and B , with different constant refractive indexes n a and n b . Based on the Fermat principle, we give the motion equations of light in one-dimensional GFPCs, and calculate its transfer matrix, which is different from the conventional PCs. We choose the linearity refractive index function for two mediums A and B , and find the transmissivity of one-dimensional GFPCs can be much larger or smaller than 1 for different slope linearity refractive index functions, which are different from the transmissivity of conventional PCs (its transmissivity is in the range of 0 and 1). Otherwise, we study the effect of different incident angles, the number of periods and optical thickness on the transmissivity, and obtain some new results different from the conventional PCs.

Electromagnetically induced grating based on the giant Kerr nonlinearity controlled by spontaneously generated coherence

We propose a scheme for realizing electromagnetically induced grating via the giant Kerr nonlinearity in a coherently driven four-level system with spontaneously generated coherence. In the presence of spontaneously generated coherence, Kerr nonlinearity can be enhanced with vanishing linear absorption. Thus, with a standing-wave coupling field, one can achieve a pure absorption grating, which leads the probe field to gather the zero-order direction when the detuning of the coupling field is on resonance. Moreover, we can obtain a pure phase grating, which diffracts a weak probe light into the first-order direction and the second-order direction when the detuning of the coupling field is off resonance.

Dynamically controlled optical nonreciprocity of a double-ladder system with spontaneously generated coherence in moving atomic optical lattice*

A four-level double-ladder cold atoms system with spontaneously generated coherence trapped in a moving optical lattice is explored to achieve optical nonreciprocity. When spontaneously generated coherence (SGC) is present, the remarkable contrast optical nonreciprocity of light transmission and reflection can be generated at each induced photonic bandgap in the optical lattice with a velocity of a few m/s. However, when the SGC effect is absent, the optical nonreciprocity becomes weak or even vanishing due to the strong absorption. It is found that the optical nonreciprocity is related to the asymmetric Doppler effect in transmission and reflection, meanwhile the degree and position of optical nonreciprocity can be tuned by the SGC effect and the Rabi frequency of the trigger field.

Quantum Theory of Atom Laser Cooling

In this paper, we study the laser cooling mechanisms with new Schrodinger quantum wave equation, which can describe a particle in conservative and non-conservative force field. We prove the atom in laser field can be cooled with the new theory, and predict that the atom cooling temperature T is directly proportional to the atom vibration frequency ω, which is in accordance with experiment result. PACS: 03.65.-w, 37.10.De, 37.10.Mn

A new quantum approach of one-dimensional photonic crystals

Abstract In this paper, we have presented a quantum theory to study one-dimensional photonic crystals, and give the quantum transform matrix and quantum transmissivity. We calculate the quantum transmissivity with defect layer, which include absorbing medium and active medium, and obtain some valuable results. The quantum approach can be used to study two-dimensional and three-dimensional photonic crystals.

Dirac Equation at Finite Temperature

In this paper, we propose finite temperature Dirac equation, which can describe the quantum systems in an arbitrary temperature for a relativistic particle of spin-1/2. When the temperature T=0, it become Dirac equation. With the equation, we can study the relativistic quantum systems in an arbitrary temperature.

A study on quantum mechanical approach for C60 diffraction analysis

Diffraction phenomena of large molecules had been demonstrated in many experiments, and these experiments were explained by many theoretical works. In this paper, we presented a detailed theoretical treatment of the single and double-slit diffraction of C60 with quantum theory approach, and we paid close attention to the diffraction experiment of C60 carried out by Zeilinger et al. in 1999. In double-slit diffraction, we further considered the decoherence effect, and found the theoretical results were in good accordance with experimental data.