Abstract

We analyze a polymer long-period grating (LPG) formed on the surface of a z-cut lithium-niobate (LN) few-mode waveguide for TM₀₀–TM₁₀ mode conversion. We identify and explore the turning points along the phase-matching curves of the LPGs for the achievement of ultra-broadband mode conversion. We fabricate a number of gratings with annealed proton-exchanged LN waveguides and our experimental results agree well with the theoretical results. A typical fabricated grating operating near the turning point provides a mode extinction ratio larger than 20 dB from 1550 nm to a wavelength longer than 1700 nm, and another one provides a mode extinction ratio larger than 10 dB from 1464 nm to a wavelength longer than 1700 nm. Our gratings show good thermal stability. The structure of the LPG on LN waveguide could be applied to the realization of ultra-broadband high-speed mode switches for mode-multiplexing applications.

© 2022 Optica Publishing Group

Leaky-mode long-period grating on a lithium-niobate-on-insulator waveguide

Wei Jin and Kin Seng Chiang
Optica 8(12) 1624-1631 (2021)

Ultra-broadband fiber mode converter based on apodized phase-shifted long-period gratings

Yunhe Zhao, Zuyao Liu, Yunqi Liu, Chengbo Mou, Tingyun Wang, and Yongsheng Yang
Opt. Lett. 44(24) 5905-5908 (2019)

Mode switch based on electro-optic long-period waveguide grating in lithium niobate

Wei Jin and Kin Seng Chiang
Opt. Lett. 40(2) 237-240 (2015)

Ultrasensitive refractometer based on helical long-period fiber grating near the dispersion turning point

Shen Liu, Min Zhou, Zhe Zhang, Zhongyuan Sun, Zhiyong Bai, and Yiping Wang
Opt. Lett. 47(10) 2602-2605 (2022)

Femtosecond laser inscribed parallel long-period fiber gratings for multi-channel core mode conversion

Chen Jiang, Kaiming Zhou, Bing Sun, Zhiqiang Wang, Ying Wan, Yuehui Ma, Chengbo Mou, Lei Shen, Lei Zhang, Jie Luo, and Yunqi Liu
Opt. Lett. 47(13) 3207-3210 (2022)