Author(s): Zhang, ZY (Zhang, Zanyun); Zhang, KX (Zhang, Kaixin); Cheng, Q (Cheng, Qian); Li, MX (Li, Meixin); Liu, TJ (Liu, Tianjun); Huang, BJ (Huang, Beiju); Zhang, Z (Zhang, Zan); Liu, HW (Liu, Hongwei); Li, HQ (Li, Hongqiang); Niu, PJ (Niu, Pingjuan); Chen, HD (Chen, Hongda)

Source: IEEE JOURNAL OF QUANTUM ELECTRONICS Volume: 57 Issue: 5 DOI: 10.1109/JQE.2021.3095289 Published: OCT 2021

Abstract: A two-dimensional grating coupler (2D GC) with four access waveguides is proposed and demonstrated for polarization independent and perfectly vertical coupling. Benefitting from the perfectly vertical coupling and 1 x 4 power splitting/combing scheme, broadband polarization independent operation can be achieved. Through grating apodization with etched square holes, a simulated coupling efficiency (CE) of 65% (-1.87 dB) is obtained with a minimum feature size of 180nm which is compatible with the 193-nm deep UV lithography technology. To characterize the device performance, a back-to-back configuration of this 2D GC was fabricated, where phase-delay lines with similar patterns are introduced to ensure the phase equality between different waveguide arms. A CE of 49% (-3.1 dB) was experimentally measured, with a 1-dB bandwidth of 42 nm and PDL below 0.2 dB across the wavelength range from 1.5 mu m to 1.6 mu m. The fibre misalignment tolerance of this device was also investigated by measurement. The excess coupling loss and PDL caused by +/- 2 mu m fibre misalignment are lower than 1 dB and 0.8 dB respectively, and the maximum excess coupling loss and PDL caused by +/- 2 degrees fibre angle error is 1 dB and 0.7 dB respectively. Finally, optical modulation using this device is preliminarily demonstrated by the embedded thermaloptic functions.

Accession Number: WOS:000681116400002

ISSN: 0018-9197

eISSN: 1558-1713

Full Text: https://ieeexplore.ieee.org/document/9475961