Nano-fabrication and characterization of silicon meta-surfaces provided with Pancharatnam-Berry effect

TL;DR

This paper demonstrates the design, fabrication, and optical characterization of silicon-based Pancharatnam-Berry meta-surfaces at 1310 nm, enabling complex phase manipulations for telecom applications.

Contribution

It presents a comprehensive approach to creating and testing silicon meta-surfaces with Pancharatnam-Berry effects, including novel fabrication and assembly of complex optical elements.

Findings

Achieved a { extpi}-phase delay with high diffraction efficiency.

Successfully fabricated silicon-based sub-wavelength gratings for telecom wavelengths.

Demonstrated complex phase pattern generation using assembled meta-surfaces.

Abstract

In this paper, the implementation of optical elements in the form of Pancharatnam-Berry optics is considered. With respect to 3D bulk and diffractive optics, acting on the dynamic phase of light, Pancharatnam-Berry optical elements transfer a phase which is geometric in nature by locally manipulating the polarization state of the incident beam. They can be realized as space-variant sub-wavelengths gratings that behave like inhomogeneous form-birefringent materials. We present a comprehensive work of simulation, realization, and optical characterization at the telecom wavelength of 1310 nm of the constitutive linear grating cell, whose fabrication has been finely tuned in order to get a {\pi}-phase delay and obtain a maximum in the diffraction efficiency. The optical design in the infrared region allows the use of silicon as candidate material due to its transparency. In order to demonstrate the possibility to assemble the single grating cells for generating more complex phase patterns, the implementation of two Pancharatnam-Berry optical elements is considered: a blazed grating and an optical vortices demultiplexer.