Polarization-separating Alvarez metalens

The rapid advancements in optical communication technologies have highlighted traditional optical components' limitations, particularly in size, adaptability, and integration capabilities, underscoring the need for more compact and versatile solutions. Metalenses offer a promising pathway to address these challenges, with their ability to provide high-functionality, miniaturized optical components. We developed a varifocal metalens with a polarization separation function designed for the wavelength of 1550 nm for potential application for next-generation communication technologies. To integrate the varifocal and polarization separation functions, polarization-dependent phase profiles for an off-axis Alvarez lens were derived and encoded by amorphous silicon pillar meta-atoms with rectangular cross sections to provide independent 0-2π phase delays for both orthogonal linear polarization components. The fabricated metalens achieved a varifocal range of 0.75 mm to 10.65 mm and a polarization extinction ratio of 18.5 dB.