Evaluation of the efficiency of radiation input into photonic integrated circuits based on thin-film lithium niobate

The calculation of the efficiency of end-face radiation input into X-cut thin-film lithium niobate photonic integrated circuits is considered for various configurations of input elements, including a straight waveguide, an inverted taper, and a horn. For each configuration, the dependence of optical losses on the position of the optical fiber relative to the waveguide, as well as on the value of the mode field radius of the optical fiber, is shown.