  Lithium niobate is a multi-functional material, which has been regarded as
one of the most promising platform for the multi-purpose optical components and
photonic circuits. Targeting at the miniature optical components and systems,
lithium niobate microstructures with feature sizes of several to hundreds of
micrometers have been demonstrated, such as waveguides, photonic crystals,
micro-cavities, and modulators, et al. In this paper, we presented
subwavelength nanograting metasurfaces fabricated in a crystalline lithium
niobate film, which hold the possibilities towards further shrinking the
footprint of the photonic devices with new optical functionalities. Due to the
collective lattice interactions between isolated ridge resonances, distinct
transmission spectral resonances were observed, which could be tunable by
varying the structural parameters. Furthermore, our metasurfaces are capable to
show high efficiency transmission structural colors as a result of structural
resonances and intrinsic high transparency of lithium niobate in visible
spectral range. Our results would pave the way for the new types of
ultracompact photonic devices based on lithium niobate.
