基于亚波长光栅辅助定向耦合器的集成铌酸锂偏振分束器OACSTPCD

Lithium niobate on insulator(LNOI)is an ideal platform for realizing high-speed photonic integrated circuits(PICs).By taking full advantage of LN,the LNOI platform enables high-speed electro-optic and efficient nonlinear optical integrated devices.The polarization beam splitter(PBS)is one of the key passive devices for separating and combining two orthogonal polarized modes,which is essential for realizing on-chip polarization multiplexing systems and enhancing the data transmission capacity of photonic communication systems.In recent years,PBS has been successfully implemented based on various structures.Among them,the PBS based on subwavelength grating-assisted directional coupling structure stands out due to its excellent device performance and compact size.In this paper,we present a high-performance PBS with a subwavelength grating-assisted directional coupling structure,realized through an indirect etching scheme ofsilicon nitride-lithium niobate heterogeneous integration.Simulation results show that the device achieves a polarization extinction ratio greater than 24.49 dB in the wavelength range of 1 500 nm to 1 600 nm.Experimental data further confirms that the polarization extinction ratio of the device is greater than 18.06 dB in the wavelength range of 1 500 nm to 1 580 nm.