Characteristics of 45° photonic crystal ring resonators based on square-lattice silicon rods

Abstract

A new photonic crystal ring resonator (PCRR) configuration is provided based on two-dimensional (2D) square lattice photonic crystal (PC) silicon rods. The ring is formed by removing the line defect along M direction instead of conventional X direction. Its spectral information including transmission intensity, dropped efficiency and quality factor affected by different physical parameters and the cascaded engineering including parallel and serial configurations are numerically analyzed with 2D finite-difference time-domain (FDTD) technique. The spectral quality factor of more than 830 and dropped efficiency of 90% at 1550 nm channel can be obtained with a less than 2.2 m ring radius.Ring resonators, owing to their high spectral selectivity and wide free spectral range (FSR), have attracted growing attention in device applications [1][2][3][4][5] . Ring resonators have been successfully demonstrated in a variety of materials including optical fibers [1,6] , low index contrast dielectric materials (material index contrast n < 2, e.g., polymer [2] ), and high index contrast semiconductor materials ( n 2, e.g., SOI [3] ). Typically, systems based on the traditional optical fiber ring technology are bulky and incompatible with photonic integration. One of the most promising designs is the planarwaveguide-based integrated micro-ring resonator, also called the whispering-gallery-mode (WGM) micro-resonator. However, for WGM ring resonators, limited by the total internal reflection (TIR) confinement principle, their propagation losses increase exponentially with the reduction of ring radii. This presents a problem for scaling. In practice a lower limit is set on the ring radius of a few micrometers (e.g. 3 m). Additionally, the performance of WGM ring resonators is also highly sensitive to the surface roughness and the nano-gap between the ring resonator and the bus waveguide. On the other hand, various types of photonic crystal ringshaped waveguide resonators [7][8][9][10][11][12][13] have been reported. However, the hybrid configuration [7] can , t further reduce the size of resonator. The ring miniaturization of PC directional loop [8,9] is limited by the required long coupling length. In the PC self-collimated loop structure [10,11] , self-collimation can only exist in special propagation directions and within a certain self-collimated frequency range. PCRRs [12,13] have attracted great interest [14][15][16] for their scalable ring sizes and flexible mode coupling configurations. Potentially, PCRRs present a solution to overcome the scaling obstacle of traditional WGM resonators.Here we present a new configuration of PCRR based on the square-lattice PC pattern by forming the ring resonator along M direction (removing one line of rods along M direction) instead of previously demonstrated X direction. The performance of new PCRR is investigated by using 2D FDTD.The schematic diagram of proposed 45° PCRR is shown in Fig.1(a), which is a square lattice with silicon rods in air (refractive index n Si =3.48 and n air =1). ...

Design and optimization of diamond-shaped biosensor using photonic crystal nano-ring resonator

“…The PCRR based structures that have been reported so far are: (1) Square and quasi-square-shape PCRR, (2) Dual curved-shape PCRR, (3) L-shape PCRR, (4) 45-deg-square shape PCRR, (5) T-shape PCRR, (6) X-shape PCRR, (7) Hexagonal-shape PCRR, and (8) Diamond-shape PCRR [21][22][23][24][25][26][27]. Most of these structures have been proposed for optical channel-drop or add-drop filters.…”

Performance improvement of wavelength division multiplexing based on photonic crystal ring resonator

“…Recently, Channel drop filters based on 2D photonic crystals with square and hexagonal lattices have attracted much attention [3][4][5][6]. In this regard, several kinds of CDF based on 2D photonic crystal ring resonator (PCRR) have been presented by using the quasisquare PCRR [7][8], square PCRR, dual square PCRR [9], dual curved PCRR [10], hexagonal PCRR [11], 45° PCRR [12], circular PCRR [3][4] and X-shaped PCRR [5].…”