range of optical functions. [1][2][3][4] Enormous developments in recent years on metamaterials, photonic and plasmonic nanostructures have demonstrated novel optical functionalities such as negative refractive index, large positive refractive index, high harmonic generations, and enhanced optical nonlinearities. [5][6][7][8][9] These novel properties lead to promising device demonstrations including superlenses, biosensors, subwavelength imaging, nanolasers, waveguides, etc., which are all important optical components for future photonic integrated circuits. [5][6][7][8][9] To integrate all the photonic structures and functionalities effectively, hybrid materials in a thin film fashion with versatile optical properties and easy on-chip device integration are very much needed.Hybrid materials consisting of metals and dielectric oxides as metamaterials have presented enormous potentials in achieving novel optical properties for the proposed optical components. In particular, gold (Au)-based hybrid materials have been widely explored for the applications in nanoscale photonic structures, such as nanophotonic switch, molecular trapping and detection, wavelength selective components, and nanophotonic waveguide. [10][11][12][13] Currently, most of the Au-based hybrid materials are fabricated by "top-down" methods, where the Au nanoparticles (NPs) are deposited on top of the substrates and then followed by a set of lithography and patterning processes using direct laser writing, e-beam lithography, or focused ion beam methods. [14][15][16] Another approach is by "bottom-up" templated-assisted electroplating methods. [6,17,18] However, both techniques involve multiple steps and tedious lithography and patterning process for largescale process. Thus, the research efforts in achieving nanoscale Au-based hybrid material systems remain as a focus.In terms of the selection of oxide dielectric materials, LiNbO 3 (LNO) has attracted great research interest in the past two decades, because of its multifunctional properties including ferroelectric, piezoelectric, pyroelectric, electro-optics, acousto-optical, birefringence, and nonlinear optical properties. [19][20][21][22][23][24][25][26][27][28] LNO also presents enormous potentials in optical devices, such as electro-optical and acousto-optical modulators, Photonic integrated circuits require various optical materials with versatile optical properties and easy on-chip device integration. To address such needs, a well-designed nanoscale metal-oxide metamaterial, that is, plasmonic Au nanoparticles embedded in nonlinear LiNbO 3 (LNO) matrix, is demonstrated with tailorable optical response. Specifically, epitaxial and single-domain LNO thin films with tailored Au nanoparticle morphologies (i.e., various nanoparticle sizes and densities), are grown by a pulsed laser deposition method. The optical measurement presents obvious surface plasmon resonance and dramatically varied complex dielectric function because of the embedded Au nanoparticles, and its response can be well tailore...