Ultra-broadband 1 × 2 3 dB power splitter using a thin-film lithium niobate from 1.2 to 2 µm wave band

The 3 dB power splitters are fundamental building blocks for integrated photonic devices. As data capacity requirements continue to rise, there is a growing interest in integrated devices that can accommodate multiple spectral bands, including the conventional O-, C-, and L-bands, and the emerging 2 µm band. Here we propose and experimentally demonstrate a 3 dB power splitter based on adiabatic mode evolution using a thin-film lithium niobate, with ultra-broadband operation bandwidth from 1200 to 2100 nm. The fabricated power splitter exhibits low insertion losses of 0.2, 0.16, and 0.53 dB for wavelengths at 1310, 1550, and 2000 nm, respectively. The measured 1 dB bandwidth covers 1260-1360, 1480-1640, and 1930-2030 nm, which we believe that the proposed device is capable of operating in both O-, C-, L-, and 2 µm bands.