Efficient second-harmonic generation in high Q-factor asymmetric lithium niobate metasurfaces

Lithium niobate (LN) has been widely used for second-harmonic generation (SHG) from bulk crystals. Recent studies have reported improved SHG efficiency in LN micro-ring resonators and hybrid waveguiding structures, as well as in LN nanostructures supporting anapole modes and plasmon-assisted dipole resonances. Here we numerically demonstrate that high Q-factor resonances associated with symmetry-protected bound states in the continuum can lead to highly efficient frequency doubling in LN metasurfaces. Simulations show that the radiative Q-factor and on-resonance field enhancement factor observed in the metasurface are closely dependent on the asymmetric parameter α of the system. Furthermore, high Q-factor resonances boost the SH conversion process in the LN nanostructures. In particular, for a LN metasurface with a Q-factor of ∼ 8 × 104, a 0.49% peak SH conversion efficiency is achieved at a pump intensity of 3.3 kW/cm2. This suggests that such high Q-factor LN metasurfaces may be good candidates for practical blue–ultraviolet light sources. Our work provides insight into the possible implementation of metadevices based on nanoengineering of conventional nonlinear crystals.

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Work Title Efficient second-harmonic generation in high Q-factor asymmetric lithium niobate metasurfaces
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Open Access
Creators
  1. Lei Kang
  2. Huaguang Bao
  3. Douglas H. Werner
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. Optics Letters
Publication Date February 1, 2021
Publisher Identifier (DOI)
  1. https://doi.org/10.1364/OL.413764
Deposited November 15, 2021

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  • Added Creator Lei Kang
  • Added Creator Huaguang Bao
  • Added Creator Douglas H. Werner
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