TE/TM-pass polarizers based on lateral leakage in a thin film lithium niobate–silicon nitride hybrid platform

Abstract

TE/TM-pass polarizers based on the lithium niobate–silicon nitride hybrid platform are numerically proposed for the first time, to the best of our knowledge. By utilizing the lateral leakage of a shallowly etched rib waveguide, 1-mm-long TE/TM-pass polarizers with high extinction ratios of 28.72/24.03 dB are obtained. Because of the anisotropy of the lithium niobate, the lateral leakage of TE/TM polarization modes can occur along crystallographic z / y directions, respectively. Such TE/TM-pass polarizers can be integrated in the same wafer.

Advances in lithium niobate photonics: development status and perspectives

“…In addition, mode-related devices, 131,244,250,251,255,261,262,267 TO-based devices, [85][86][87] Bragg grating filters, 253,256,257,264 optical true delay lines, 263 and optical phased arrays 260 have also been demonstrated in the LN platform. Most of them rely on the large refractive index contrast available in TFLN.…”

Integrated Subwavelength Gratings on a Lithium Niobate on Insulator Platform for Mode and Polarization Manipulation

“…On the other hand, lateral leakage has also been proposed to realize TE/TMpass polarizers by differentiating the propagation loss of TE and TM modes in a waveguide. [38,39] This kind of device is expected to have low loss and high PER. However, the devices are usually required to be from hundreds of micros to one millimeter long, which are somewhat bulky for large-scale integration.…”

“…The total length of the device is ≈55 μm, with the length of taper waveguides included, which is reduced greatly compared to that reported in previous work on the same platform (≈1000 μm). [ 38 ] Figure 3d shows the simulated electric field profiles for TE 0 and TM 0 modes input into the device, at a wavelength of 1550 nm. Figure 3e shows the simulated transmission spectra of different light polarization modes as a function of the input wavelength.…”

Mode and Polarization‐Division Multiplexing Based on Silicon Nitride Loaded Lithium Niobate on Insulator Platform

“…The TE polarizer is formed by a straight waveguide with a width of w 8 =0.6 µm, where the transmission loss of the TM 0 mode at a wavelength of 1550 nm is estimated to be over 100 dB cm −1 due to the lateral leakage while the loss of TE 0 mode is negligible. [ 36 ] In this work, the length of the TE polarizer is set to L 6 =300 µm, which can be further increased if higher extinction ratios are required. Linear tapered waveguides with optimized lengths are used to connect the straight waveguides with different widths.…”