Mode analysis of photonic crystal polarization beam splitter and its application in integrated circuits design

Abstract

ABSTRACT In this work, the guided modes of a photonic crystal polarization beam splitter (PC-PBS) are studied. We demonstrate that the transmission of a low-loss photonic crystal 120° wave guide bend integrated with the PBS will be influenced if the PBS is multi-moded. We propose a single-moded PC-PBS structure by introducing deformed structures, and it shows twice the enhancement of the transmission. This device with remarkable improvement of performance is promising in the use of photonic crystal integrated circuits design. Keywords: Photonic crystal, Polarization beam splitter, Wa veguide bends, Photonic integrated circuits 1. INTRODUCTION A polarization beam splitter (PBS) is one of the key functional bricks for photonic integrated circuits. The device lengths of conventional PBSs are usually hundreds of microns [1], which is disadvantageous to the enhancement of integration density. Photonic crystal (PC) is consider ed to be one of the most promising candidates for high density integration [2-3]. Recently, a PBS based on PC shows significantly shortened de vice length and good performa nce [4], therefore it shows great advantage in the use of PC circuits. Another important device for the PC integrated circuit is the low-loss waveguide bend [5]. In order to connect different functional units of circuit, it is crucial that the waveguide bend should have the ability of guiding light through sharp corner with high efficiency. It is frequently discussed that the transmission is mostly determined by the bend structure itself, and various low-loss bend structures with different guiding mechanisms have been proposed [6-7]. However, in the optical integrated circuits, it is inevitable that the impact of one device to another should be considered. In this paper, we focus on the integration of a PC-PBS and a low-loss PC waveguide bend. We show that transmission will be determined not only by the bend structure, but also by the mode characteristics of the PC-PBS. Finally, we propose an optimized PC-PBS structur e, which effectively improves the pe rformance of the integrated unit.