Low-loss and low-crosstalk 8 × 8 silicon nanowire AWG routers fabricated with CMOS technology.

Jing Wang,Zhen Sheng,Minghao Qi,Fuwan Gan,Wei Li,Le Li,Albert Pang,Shichang Zou,Xi Wang,Aimin Wu

doi:10.1364/oe.22.009395

Abstract

Low-loss and low-crosstalk 8 × 8 arrayed waveguide grating (AWG) routers based on silicon nanowire waveguides are reported. A comparative study of the measurement results of the 3.2 nm-channel-spacing AWGs with three different designs is performed to evaluate the effect of each optimal technique, showing that a comprehensive optimization technique is more effective to improve the device performance than a single optimization. Based on the comprehensive optimal design, we further design and experimentally demonstrate a new 8-channel 0.8 nm-channel-spacing silicon AWG router for dense wavelength division multiplexing (DWDM) application with 130 nm CMOS technology. The AWG router with a channel spacing of 3.2 nm (resp. 0.8 nm) exhibits low insertion loss of 2.32 dB (resp. 2.92 dB) and low crosstalk of -20.5~-24.5 dB (resp. -16.9~-17.8 dB). In addition, sophisticated measurements are presented including all-input transmission testing and high-speed WDM system demonstrations for these routers. The functionality of the Si nanowire AWG as a router is characterized and a good cyclic rotation property is demonstrated. Moreover, we test the optical eye diagrams and bit-error-rates (BER) of the de-multiplexed signal when the multi-wavelength high-speed signals are launched into the AWG routers in a system experiment. Clear optical eye diagrams and low power penalty from the system point of view are achieved thanks to the low crosstalk of the AWG devices.

Highlights

Arrayed waveguide grating (AWG) has become a key component in commercial wavelengthdivision multiplexing (WDM) systems for its multichannel wavelength selective function [1]
AWG based on silicon nanowire waveguides [5–11] has attracted much attention for its compact size owing to the high-index-contrast property of the silicon-on-insulator (SOI) waveguide, which allows for sharp bends
Its fabrication is compatible with CMOS technology, offering a promising solution for large-scale integration with other silicon-based devices in a highdensity photonic chip

Summary

Introduction

Arrayed waveguide grating (AWG) has become a key component in commercial wavelengthdivision multiplexing (WDM) systems for its multichannel wavelength selective function [1]. It is well known that the Si nanowire AWG has worse crosstalk performance than the low-index-contrast device due to its increased sensitivity to the phase error of the arrayed waveguides. Based on the optimal design and well-controlled 130 nm CMOS fabrication process, a new high-performance Si nanowire AWG router with 0.8 nm channel spacing for DWDM application is successfully demonstrated. The waveguide sidewall roughness induces fluctuations of the effective index and degrades the imaging quality at the output waveguides For this AWG, considerable optical power of certain wavelength enters into the unwanted output channels and the received power in the desirable channel is reduced, which leads to both poor crosstalk performance and large insertion loss. Based on the comprehensive optimal design and well-controlled 130 nm CMOS fabrication process mentioned above, a high-performance Si nanowire AWG (#4) router with 0.8 nm channel spacing is successfully demonstrated. Some post-fabrication tuning technology (e.g. thermal tuning [15]) can be further used for wavelength adjustment

Multi-wavelength high-speed system demonstration

Conclusion