Design of novel power splitters by directional coupling between photonic crystal waveguides

Abstract

The design of a novel photonic crystal waveguide power splitter is presented. The proposed power splitter has three output ports, the coupling among three parallel photonic crystal waveguides can be considered as a multimode interference (MMI), and the positions of output waveguides are determined by those of twofold images which are formed by the self-imaging effect of multimode interference. The transmission characteristics of the splitter are investigated by using the finite-difference time domain (FDTD) and the plane wave expansion method. The output optical power in each port can be controlled by adjusting the radius of the dielectric rods in the coupling region, and the coupling effect among output ports is decreased by using the T-shaped output port. The results indicate that 1 1 1 2 and 1 3 type power splitters can be realized when the normalized radius of dielectric rods in the coupling region is 0.130, 0.180, 0.152 or 0.221, respectively.Photonic crystals (PCs) [1,2 ] have defect modes [3] in the band gaps by introducing defects in perfect photonic crystals, and optical waveguides can be constructed by introducing linear defects which confirm that there is no radiation loss through sharp bends in photonic crystal waveguides [4] . The directional coupling can happen between two or more photonic crystal waveguides, based on which couplers such as splitters [5] , optical switchng [6] and wavelength division multiplexer/ demultiplexer (WDMD) [7] can be formed. Multimode interference (MMI) [8] devices based on self-imaging effect [9] are important components in photonic integrated devices. Due to their simple structure, low loss, and large optical bandwidth, we can design all optical switching [10] , TE/TM polarization splitter [11] and filter [12] . MMI devices have been widely used in the field of optical communications.The design of a novel photonic crystal power splitter is reported in this paper. The coupling among three parallel photonic crystal waveguides can be considered as a multimode interference, and the positions of output waveguides are determined by those of twofold images formed by the self-imaging effect of multimode interference. The 1 1, 1 2 and 1 3 type splitters can be realized based on the same structure.The structure is the dielectric rod photonic crystal with two-dimensional (2D) square lattice surrounded by the air (n l = 1.00), and the dielectric constant is r = 11.56. The ratio of rod radius to lattice constant is set to be 0.18. The coupling among three parallel photonic crystal waveguides can be considered as a multimode interference. Selecting the supercell shown in Fig.1 and using the plane wave expansion method [13] , the dispersion curve of the photonic crystal multimode waveguide can be solved, which is shown in Fig.2. Influenced by the self-imaging effect of multimode interference, the position of 1-fold image is determined byThe position of 2-fold image is determined by L = 2 k/( 0 2 ) k=1, 2, 3,(1) L = (2k 1) ( 0 2 ) k=1,2,3,where 0 = 0.3150 2 /a and 2 = 0.2746 2 /a at a/...

Off-plane directional coupler in woodpile structure

“…It is possible to realize various active and passive optical devices in PCs which include cavity or waveguide. Over the past few years, various optoelectronic devices based on two dimensional (2D) PCs [5][6][7][8][9][10][11][12][13][14][15][16], such as power splitters [10][11][12], wavelength division multiplexers (WDM) [13,14] and channel drop filters [15,16], have been already reported theoretically and experimentally. In these devices, directional couplers [5][6][7][8][9] that the light wave can be coupled completely from one waveguide to another waveguide are very important.…”

Luminescence enhancement from Si-based materials by introducing a photonic crystal double-heterostructure slot waveguide microcavity

“…Nevertheless, the light emission from current Er-doped SiO 2 materials is too weak for practical applications. There are many methods proposed to fabricate Er-doped SiO 2 materials, among which the sol-gel [1] technology has attracted much attention, which has the advantages of low operating temperature, accurate control of doping, high concentration and uniformity of doping, etc.Photonic crystals (PCs) [2][3][4] have been shown to be an excellent means of controlling the interaction between light and matter. By introducing some point defects in perfect PC structures to form microcavity, the enhancement of luminescence at the resonant frequency can be realized by the mode confinement effect of microcavity [5][6][7][8][9] .…”

“…Photonic crystals (PCs) [2][3][4] have been shown to be an excellent means of controlling the interaction between light and matter. By introducing some point defects in perfect PC structures to form microcavity, the enhancement of luminescence at the resonant frequency can be realized by the mode confinement effect of microcavity [5][6][7][8][9] .…”