Two-dimensional Triangular Lattice Photonic Crystals Research Articles

金属嵌入对三角晶格耦合腔光波导群速度的影响

The transmission characteristics of the coupled-resonator optical waveguides based on the two-dimensional triangular-lattice photonic crystal are studied by the multiple-scattering methods and the finite-difference time-domain method.Through selective inserting the rods with different radius between two adjacent microcavities,the coupling intensity between the two adjacent point defects is weaken,and the group velocity can be further reduced by three orders of magnitude.

Reconfigurable multimode photonic-crystal waveguides

We present the design and analysis of a novel reconfigurable photonic-crystal waveguide (PCW). The predefined waveguide is the result of the refractive-index variation of three rows of holes that can be obtained by the infiltration of liquids within what are otherwise air holes in a two-dimensional triangular-lattice photonic crystal. We compute the power transmission through the reconfigurable PCWs as well as through arbitrary waveguide bends. The advantages of writing reconfigurable PCW of a multimode nature are highlighted. We demonstrate the necessity to infiltrate high-refractive-index substances to obtain efficient power transfer via reconfigurable manner.

Channel drop filter in two-dimensional triangular lattice photonic crystals

Based on two-dimensional photonic crystals with a triangular lattice, a channel drop filter with a wavelength-selective reflection microcavity is designed. In the structure, two microcavities are used. One is used for a resonant tunneling-based channel drop operation. The other is used to realize wavelength-selective reflection feedback in the bus waveguide. The phase term, which is derived by means of coupled-mode theory to achieve close to 100% drop efficiency, is satisfied by modifying the sizes of the border air holes next to the bus waveguide section between the two cavities. Using the finite-difference time-domain method, the simulation results show complete power transfer between the bus and drop waveguides via the system.

Graded index photonic crystals

We explore two-dimensional triangular lattice photonic crystals composed of air holes in a dielectric background which are subject to a graded-index distribution along the direction transverse to the propagation. The proper choice of the parameters such as the input beam width, gradient coefficient, and the operating frequency allow the realizations of the focusing (lens) and guiding (waveguide) effects upon which more complex optical devices such as couplers can be designed. Numerical results obtained by the finite-difference time-domain and planewave expansion methods validate the application of Gaussian optics within a range of parameters where close agreement between them are observed.

Imaging properties of triangular lattice photonic crystal at the lowest band

The propagation of electromagnetic (EM) waves in two-dimensional triangular-lattice photonic crystals (PCs) is investigated through dispersion characteristics analysis and numerical simulation of field pattern. We examine different surface terminations of the PC slab for getting a high-quality image. In the lowest photonic band both the TM and TE polarized EM waves can undergo negative refraction and imaging effect even at frequencies above the light line. The dependence of the image on the object distance and sample thickness is also discussed.

Transmission of photonic crystal coupled-resonator waveguide (PhCCRW) structure enhanced via mode matching

A method for increasing the coupling efficiency between ridge optical waveguides and PhCCRWs is described. This increase is achieved via W1 channel waveguide sections, formed within a two-dimensional triangular lattice photonic crystal using mode-matching. The mode-matching is achieved by low quality-factor modified cavities added to both the input and output ports of the PhCCRW. A three dimensional finite-difference time-domain method has been used to simulate light propagation through the modified PhCCRW. We have fabricated PhCCRWs working at 1.5microm in silicon-on-insulator material. Measurements and simulations show that the overall transmission is improved by a factor of two.

Transverse magnetic defect modes in two-dimensional triangular-lattice photonic crystals.

We present a numerical study of the localized transverse magnetic (TM) defect modes in a two-dimensional, triangular-lattice photonic crystal. The sample consists of an array of circular, air cylinders in a dielectric medium (GaAs). The defect modes were calculated by using a parallel version of the finite-difference time-domain method on the Yee mesh. To validate our computations the results for the transverse electric case were checked against experimental results and the numerical results using a different method. We study the spatial symmetry for TM modes, obtained by changing the dipole excitation frequency. Also, we vary the defect-cylinder radius to tune the resonant frequency across the band gap. The TM mode is found to be highly localized at the defect in the photonic lattice.