Single-step etched grating couplers for silicon nitride loaded lithium niobate on insulator platform
Xu Han,
Yongheng Jiang,
Andreas Frigg,
Huifu Xiao,
Pu Zhang,
Andreas Boes,
Thach G. Nguyen,
Jianhong Yang,
Guanghui Ren,
Yikai Su,
Arnan Mitchell,
Yonghui Tian
Affiliations
Xu Han
Institute of Microelectronics and Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, Gansu, China
Yongheng Jiang
Institute of Microelectronics and Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, Gansu, China
Andreas Frigg
Integrated Photonics and Applications Centre (InPAC), School of Engineering, RMIT University, Melbourne, Victoria 3001, Australia
Huifu Xiao
Institute of Microelectronics and Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, Gansu, China
Pu Zhang
Institute of Microelectronics and Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, Gansu, China
Andreas Boes
Integrated Photonics and Applications Centre (InPAC), School of Engineering, RMIT University, Melbourne, Victoria 3001, Australia
Thach G. Nguyen
Integrated Photonics and Applications Centre (InPAC), School of Engineering, RMIT University, Melbourne, Victoria 3001, Australia
Jianhong Yang
Institute of Microelectronics and Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, Gansu, China
Guanghui Ren
Integrated Photonics and Applications Centre (InPAC), School of Engineering, RMIT University, Melbourne, Victoria 3001, Australia
Yikai Su
The State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Arnan Mitchell
Integrated Photonics and Applications Centre (InPAC), School of Engineering, RMIT University, Melbourne, Victoria 3001, Australia
Yonghui Tian
Institute of Microelectronics and Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, Gansu, China
Dielectrically loaded thin-film lithium niobate (LiNbO3) on insulator (LNOI) platforms have enabled a range of photonic integrated circuit components, such as high-speed optical modulators, switches, and nonlinear devices, while avoiding the direct etching of the LiNbO3 thin film. Silicon nitride (Si3N4) is one of the most attractive dielectric loading materials as it has a similar refractive index and transparency window to LiNbO3 and can be deposited and patterned by mature fabrication processes. The patterning of Si3N4 opens the opportunity to fabricate grating couplers in the same fabrication step, providing efficient optical interfaces for wafer-scale testing. In this paper, we investigate and demonstrate single-step etched grating couplers on a Si3N4-LNOI (X-cut) platform. The grating couplers (straight and curved) are designed and fabricated for TE-polarized modes along the Y and Z crystallographic directions, considering the LiNbO3 crystal’s birefringence. The experimentally demonstrated coupling losses are as low as 4.02 and 4.24 dB along the crystallographic Y and Z directions, respectively. The corresponding peak wavelengths are 1609 and 1615 nm, respectively. The measured 3-dB bandwidths are wider than 70 nm for both crystallographic directions. We also numerically investigated the influence of fabrication variations and the fiber angle on the transmission. To the best of our knowledge, this work is the first demonstration of grating couplers with different light propagation directions on the Si3N4 loaded LNOI platform.
