Abstract We propose a broadband and compact polarization splitter-rotator (PSR) based on thin-film lithium niobate, which consists of a triple-taper asymmetric directional coupler (ADC), a linear taper, and an S-bend. The device employs a tapered structure with a gradual width gradient to maintain approximate phase-matching conditions across a broad bandwidth, while leveraging mode-coupling principles to achieve compact dimensions. Numerical simulations show that the device has insertion losses (IL) of less than 0.56 dB over the entire C-band range. At the wavelength of 1550 nm, The device exhibits an IL below 0.53 dB, and an extinction ratio (ER) exceeding 28.5 dB. The device maintains insertion losses less than 1.29 dB and ERs more than 20.9 dB across a 210 nm wide bandwidth. The device length is 60 μm, of which the coupling region is only 26.1 μm. This device exhibits significant potential for applications in polarization-division multiplexing transceivers, on-chip polarization controllers, and high-density photonic integrated circuits.
CHEN et al. (2025) studied this question.