Anisotropic subwavelength grating device for ultra-broadband polarization splitting and TM-mode power division

Multifunctional integrated photonic devices are essential for advancing high-density photonic circuits. In this work, we propose and experimentally demonstrate an ultra-broadband device that simultaneously enables polarization separation and 3 dB power splitting for the TM mode. The design exploits the anisotropic properties of subwavelength gratings (SWGs), incorporating transverse and longitudinal SWGs in both transition and coupling regions. TE-polarized light is guided through the central path, while TM-polarized light is symmetrically split into lateral SWGs. The device functions as a broadband polarizer for TE input (1260-1675 nm), with excess loss (EL) below 1 dB and crosstalk (CT) below -20 dB. For TM input, 3 dB splitting is achieved over 1400-1660 nm, with EL < 0.5 dB and CT < -22 dB at 1550 nm. The compact footprint (21 × 6 µm²) and CMOS-compatible fabrication further enhance its practical relevance. Experimental results confirm efficient dual-function performance, with low loss and high polarization extinction across a wide bandwidth.