A LiNbO₃ Platform with Tailored Thickness Bridging Bulk and Thin Film: Application to Broadband Frequency Conversion

We introduce a monolithic LiNbO3 membrane platform that bridges bulk and thin-film approaches, enabling custom-tailored waveguide cross sections. Using a combination of saw dicing and reactive ion etching (RIE), we fabricate LiNbO3 structures with adaptable thicknesses ranging from 400 nm to several microns, identifying 2 μm as an optimal value for addressing key challenges in frequency conversion. Our platform demonstrates robust second harmonic generation (SHG) with a broad pump wavelength response of up to 150 nm within the C-band at room temperature, achieved by tuning the waveguide thickness, while maintaining low coupling losses of 0.8 dB/facet. These results represent a significant step toward versatile integrated photonic systems, advancing applications in broadband spectroscopy, quantum information processing, and sensing through efficient and spectrally agile nonlinear frequency conversion.