Two-dimensional displacement sensors with angstrom-scale resolution based on optical slot antenna arrays

Abstract

Optical displacement sensing with high resolution and noncontact detection plays an important role in nanometrology, nanofabrication, and super-resolution microscopy. However, displacement sensing along an arbitrary direction in a two-dimensional (2D) plane with angstrom-level precision remains challenging. Here, we propose a 2D displacement sensor composed of eight optical slot antennas. A tightly focused laser beam is illuminated upon the antennas. The amplitudes and phases of the output radiation of the antennas are controlled by geometries. The intensity distribution of the output far-field radiation, which strongly depends on the relative position between the focal spot of the incident light and the antennas, was used to retrieve the 2D coordinates of any location in a plane. A resolution as high as 0.88 nm was obtained. We also show a method for improving displacement sensitivity by designing the destructive interference among the radiation of the antennas. The angstrom-scale resolution and arbitrary point localization, along with the nanoscale size, pave the way for the development of high-performance sensing, integrated photonic circuits, and on-chip signal processing.