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Title: 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 highQ-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 radiativeQ-factor and on-resonance field enhancement factor observed in the metasurface are closely dependent on the asymmetric parameterα<#comment/>of the system. Furthermore, highQ-factor resonances boost the SH conversion process in the LN nanostructures. In particular, for a LN metasurface with aQ-factor of∼<#comment/>8×<#comment/>104, a 0.49% peak SH conversion efficiency is achieved at a pump intensity of3.3kW/cm2. This suggests that such highQ-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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PAR ID:
10211466
Author(s) / Creator(s):
; ;
Publisher / Repository:
Optical Society of America
Date Published:
Journal Name:
Optics Letters
Volume:
46
Issue:
3
ISSN:
0146-9592; OPLEDP
Format(s):
Medium: X Size: Article No. 633
Size(s):
Article No. 633
Sponsoring Org:
National Science Foundation
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