Tunable optical delay line based on integrated grating-assisted contradirectional couplers
Tunable optical delay lines are one of the key building blocks in optical communication and microwave systems. In this work, tunable optical delay lines based on integrated grating-assisted contradirectional couplers are proposed and experimentally demonstrated. The device performance is comprehensively improved in terms of parameter optimization, apodization analysis, and electrode design. Tunable group delay lines of 50 ps at different wavelengths within the bandwidth of 12 nm are realized with a grating length of 1.8 mm. Under thermal tuning mode, the actual delay tuning range is around 20 ps at 7.2 V voltage. At last, a new scheme adopting an ultra-compact reflector for doubling group delay is proposed and verified, achieving a large group delay line of 400 ps and a large dispersion value up to 5.5×106 ps/(nm·km) within bandwidth of 12 nm. Under thermal tuning mode, the actual delay tuning range is around 100 ps at 8 V voltage.
基金项目：National Natural Science Foundation of China (NSFC)10.13039/501100001809 (61475052, 61622502); Fundamental Research Funds for the Central Universities (2017KFXKJC001).
Yuhe Zhao：National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Yunhong Ding：Department of Photonics Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Sanshui Xiao：Department of Photonics Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Jianji Dong：National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
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Xu Wang, Yuhe Zhao, Yunhong Ding, Sanshui Xiao, and Jianji Dong, "Tunable optical delay line based on integrated grating-assisted contradirectional couplers," Photonics Research 6(9), 880-886 (2018)