Subwavelength Grating‐Assisted Contra‐Directional Couplers in Lithium Niobate on Insulator

Grating‐assisted contra‐directional couplers are important optical components in photonic integrated circuits (PICs), which can serve as fundamental building blocks for optical (de)multiplexers, switches, filters, and splitters, among others. Recently, lithium niobate on insulator (LNOI) has emerged...

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Bibliographic Details
Published in:Laser & photonics reviews 2023-10, Vol.17 (10)
Main Authors: Han, Xu, Jiang, Yongheng, Xiao, Huifu, Yuan, Mingrui, Nguyen, Thach Giang, Boes, Andreas, Ren, Guanghui, Zhang, Yong, Hao, Qinfen, Su, Yikai, Mitchell, Arnan, Tian, Yonghui
Format: Article
Language:English
Subjects:
Crosstalk
Directional couplers
Insertion loss
Integrated circuits
Lithium niobates
Modulators
Multiplexers
Multiplexing
Optical components
Photonics
Silicon nitride
Waveguides
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Summary:Grating‐assisted contra‐directional couplers are important optical components in photonic integrated circuits (PICs), which can serve as fundamental building blocks for optical (de)multiplexers, switches, filters, and splitters, among others. Recently, lithium niobate on insulator (LNOI) has emerged as an attractive PIC platform with many important active photonic circuit components demonstrated, including electro‐optic modulators and second‐harmonic wavelength converters. Nevertheless, the LNOI component toolbox still lacks some passive photonic circuit components to fulfill the requirements of future high‐performance PICs. In this contribution, a subwavelength grating‐assisted contra‐directional coupler (GACDC) is proposed, designed, and experimentally demonstrated in a silicon nitride‐loaded LNOI waveguide platform. As an example of its applications, a three‐channel wavelength‐division (de)multiplexer is fabricated and experimentally demonstrated by cascading several GACDCs, with a narrow wavelength spacing of 3.2 nm (400 GHz). The measured device insertion loss of each channel is about 2.5 dB with low interchannel crosstalk below −20 dB. A fabrication tolerance analysis is also carried out, indicating that the proposed GACDCs are tolerant to waveguide width variations.
ISSN:1863-8880
1863-8899
DOI:10.1002/lpor.202300203