A Polarization-Insensitive 3 dB Power Splitter Based On Inverse-Designed Subwavelength Pixelated Structure

The polarization-independent power splitters (PIPSs) are essential for enabling efficient integration in photonic circuits. In this letter, we propose and experimentally demonstrate an ultra-compact, broadband 3 dB PIPS, whose design is based on a sub-wavelength pixelated structure with a footprint of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5\times \,\, 1.5~\mu $ </tex-math></inline-formula>m2. The initial pixelated structure is carefully designed to enhance algorithm robustness of the optimization process, thereby improving efficiency and avoiding local optima. The experimental results show that the insertion loss of both TE0 and TM0 is lower than 1.5 dB within the wavelength range of 1480-1580 nm, while the beam splitting ratio between the two output ports remains above 75%. In addition, the fabrication tolerance of the device is examined to ensure low insertion loss and reflection loss. This ultra-compact on-chip device demonstrates significant potential for advancing high-density integration in optical circuits.