Mid-Infrared Optical Loss Analysis in Thin-Film Lithium Niobate Based on Thickness Gradient Method

The mid-infrared spectral region is crucial for a range of applications, including molecular spectroscopy, environmental sensing, and free-space communications, due to the presence of strong vibrational and rotational absorption bands [1]. Despite its significance, achieving efficient light manipulation and transmission in the mid-IR remains a considerable challenge. While TFLN has emerged as a promising platform for integrated photonics, its performance in the mid-IR is still hindered by unresolved optical loss mechanisms [2]–[3], such as bulk material defects, surface contamination, and chemical absorption. (Fig. 1 (a-e)) This work addresses these challenges by systematically analyzing and characterizing the mid-IR optical losses in TFLN micro-resonators.