Metrology for Measuring Custom Periodicities on Diffraction Gratings

TL;DR

This paper introduces GMAP, a cost-effective bench-top device capable of accurately measuring large-area groove periods and complex patterns on diffraction gratings, surpassing optical interferometry limitations.

Contribution

The paper presents GMAP, a novel measurement tool that enables high-resolution, accurate, and large-area measurement of diffraction grating periods, including non-parallel and customized patterns.

Findings

Achieves 0.1 mm×0.1 mm spatial resolution.

Period measurement error of 1.7 nm for 3 μm grooves.

Successfully measures complex, customized gratings.

Abstract

We present a new, inexpensive, bench-top method for measuring groove period over large areas with high mapping resolution and high measurement accuracy, dubbed the grating mapper for accurate period (GMAP). The GMAP has the ability to measure large groove period changes and non-parallel grooves, both of which cannot be measured via optical interferometry. In this paper, we detail the calibration and setup of the GMAP, and employ the instrument to measure three distinct gratings. Two of these measured gratings have customized groove patterns that prevent them from being measured via other traditional methods, such as optical interferometry. Our implementation of this tool achieves a spatial resolution of 0.1 mm$\times$0.1 mm and a period error of 1.7 nm for a 3 $\mu$m size groove period.