Compact and ultra-low-loss hybrid plasmonic waveguide polarization mode converter for efficient TE-to-TM transformation

A compact and ultra-low loss TE-to-TM polarization mode converter based on a hollow hybrid plasmonic waveguide is presented in this work. The incorporation of an air region in the hollow structure results in a refractive index as low as 1, enabling near-lossless mode propagation and conversion. Through the delicate design of multi-functional sections and the optimization of structural dimensions, efficient conversion from the TE mode to the TM mode is achieved. At the operating wavelength of 1550 nm, the converter demonstrates remarkable performance with a mode conversion efficiency of 0.88, a polarization conversion efficiency of 0.92, and an ultra-low insertion loss of 0.012 dB. Additionally, the device boasts a compact size of 8.5 µm while exhibiting excellent performance. This work offers a simple and efficient approach for realizing ultra-low-loss polarization mode conversion, holding promising potential for application in diverse integrated photonic devices.