Passive Silicon Nitride On-Chip Polarimetry: Precise Polarization Detection with Imperfect Components

TL;DR

This paper presents a compact, passive silicon nitride on-chip polarimeter that accurately measures light polarization using a novel architecture and calibration, overcoming fabrication imperfections for diverse applications.

Contribution

The work introduces a robust, integrated photonic polarimeter with a calibration method that maintains accuracy despite component imperfections, advancing miniaturized polarization measurement technology.

Findings

Achieved precise polarization detection with integrated silicon nitride chip.

Developed a calibration procedure to mitigate fabrication imperfections.

Demonstrated high-speed, small-footprint polarimetry suitable for various applications.

Abstract

Polarization is a fundamental property of light that carries distinct and valuable information. Consequently, its precise measurement is crucial for numerous applications, including biomedical imaging, remote sensing, and optical communication. Since polarization cannot be measured directly, it is typically inferred by converting it into intensity signals using dedicated optical elements. Conventional approaches, however, predominantly rely on bulky optical components, leading to considerably high fabrication costs and limited integration density. Here, we introduce a passive photonic integrated circuit capable of precisely determining the polarization state of visible free-space light. An silicon nitride on-chip architecture employing a compact polarization-splitting grating coupler and a set of passive interferometers encodes the polarization information into intensity signals, allowing conventional detectors to accurately reconstruct the polarization state. With increasing compactness of photonic components, however, susceptibility to fabrication tolerances as well as intrinsic design constraints increases, potentially leading to non\-/ideal behaviour. To address this, we introduce a robust calibration procedure that enables precise measurements even in the presence of imperfections. The chip design, combined with the calibration procedure, offers a robust, small-footprint, and high-speed approach to polarimetry, enabling a wide range of applications.