• Chinese Optics Letters
  • Vol. 19, Issue 6, 060003 (2021)
Mengyue Xu, Mingbo He, Yuntao Zhu, Lin Liu, Lifeng Chen*, Siyuan Yu**, and Xinlun Cai***
Author Affiliations
  • State Key Laboratory of Optoelectronic Materials and Technologies and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510000, China
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    Abstract

    Integrated traveling-wave lithium niobate modulators need relatively large device lengths to achieve low drive voltage. To increase modulation efficiency within a compact footprint, we report an integrated Fabry–Perot-type electro-optic thin film lithium niobate on insulator modulator comprising a phase modulation region sandwiched between two distributed Bragg reflectors. The device exhibits low optical loss and a high tuning efficiency of 15.7 pm/V. We also confirm the modulator’s high-speed modulation performance by non-return-to-zero modulation with a data rate up to 56 Gbit/s.

    1. Introduction

    Lithium niobate (LiNbO3, LN) has been the dominant material platform for optical modulators widely used in optical fiber communications due to its excellent physical properties, such as its high electro-optic (EO) Pockels coefficient, low optical absorption, high intrinsic modulation bandwidth, and long-term material reliability[1,2]. However, conventional LN modulators based on low-index-contrast optical waveguides show weak EO interactions, limiting further improvement of modulation efficiency and reduction of device size. Recently, thin film LN-on-insulator (LNOI) has emerged as a promising platform for high-performance integrated modulators, as it offers strong optical confinement and thus high integration density. Several studies have demonstrated the integrated Mach–Zehnder modulators (MZMs) with low drive voltage, low optical insertion loss, and high EO bandwidths on both the LNOI platform[3,4] and silicon-based LN hybrid platform[57]. The modulation efficiency of integrated LN modulators with dry-etched LN waveguides has increased to 2V·cm[3,8], which is significantly higher than that of conventional modulators with ion-diffused or proton-exchanged waveguides (>10V·cm). Even so, an integrated LN modulator in the traveling-wave Mach–Zehnder configuration still has modulation lengths of 1–2 cm to achieve low-voltage energy-efficient modulation. Such footprint sizes are still too large for future optical interconnect applications.

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    Mengyue Xu, Mingbo He, Yuntao Zhu, Lin Liu, Lifeng Chen, Siyuan Yu, Xinlun Cai. Integrated thin film lithium niobate Fabry–Perot modulator [Invited][J]. Chinese Optics Letters, 2021, 19(6): 060003
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    Category: Special Issue on Lithium Niobate Based Photonic Devices
    Received: Dec. 25, 2020
    Accepted: Feb. 2, 2021
    Published Online: Mar. 26, 2021
    The Author Email: Lifeng Chen (chenlf37@mail.sysu.edu.cn), Siyuan Yu (yusy@mail.sysu.edu.cn), Xinlun Cai (caixlun5@mail.sysu.edu.cn)