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  • Received: Mar. 25, 2019

    Accepted: Jul. 2, 2019

    Posted: Aug. 9, 2019

    Published Online: Aug. 9, 2019

    The Author Email: Lutong Cai (lutongc@andrew.cmu.edu)

    DOI: 10.1364/PRJ.7.001003

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    Lutong Cai, Ashraf Mahmoud, Msi Khan, Mohamed Mahmoud, Tamal Mukherjee, James Bain, Gianluca Piazza. Acousto-optical modulation of thin film lithium niobate waveguide devices[J]. Photonics Research, 2019, 7(9): 1003-1013

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Photonics Research, Vol. 7, Issue 9, 1003-1013 (2019)

Acousto-optical modulation of thin film lithium niobate waveguide devices 

Lutong Cai*, Ashraf Mahmoud, Msi Khan, Mohamed Mahmoud, Tamal Mukherjee, James Bain, and Gianluca Piazza

Author Affiliations

  • Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA

Abstract

Due to its strong piezoelectric effect and photo-elastic property, lithium niobate is widely used for acousto-optical applications. However, conventional bulk lithium niobate waveguide devices exhibit a large footprint and limited light–sound interaction resulting from the weak guiding of light. Here, we report the first acousto-optical modulators with surface acoustic wave generation, phononic cavity, and low-loss photonic waveguide devices monolithically integrated on a 500 nm thick film of lithium niobate on an insulator. Modulation efficiency was optimized by properly arranging the propagation directions of surface acoustic waves and optical guided modes. The effective photo-elastic coefficient extracted by comparing the first and third harmonic modulation signals from an on-chip Mach–Zehnder interferometer indicates the excellent acousto-optical properties of lithium niobate are preserved in the thin film implementation. Such material property finding is of crucial importance in designing various types of acousto-optical devices. Much stronger amplitude modulation was achieved in a high Q (>300,000) optical resonator due to the higher optical sensitivity. Our results pave the path for developing novel acousto-optical devices using thin film lithium niobate.