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Updated: Jun 18, 2025

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Polarization-insensitive multimode interference coupler on an x-cut thin-film lithium niobate platform
Abstract:
Thin-film lithium niobate (TFLN) is a promising integrated photonics platform but currently lacks a polarization-insensitive multimode interference (MMI) coupler, a crucial component for polarization-related optical communication applications such as polarization management, polarization-division multiplexing, and polarization-insensitive modulation systems. This paper presents a novel, to the best of our knowledge, approach by rotating the MMI structure on an anisotropic x-cut TFLN at specific angles to compensate for the difference in the beat length between the two polarizations. A polarization-insensitive 1 × 2 MMI coupler is experimentally achieved with measured transmittances of -2.5 to -4 dB for both output ports and polarization modes in the wavelength range of 1520-1580 nm.
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