# Near-Infrared Scanning Cavity Ringdown for Optical Loss Characterization of Supermirrors

## TL;DR

This paper introduces a near-infrared scanning cavity ringdown technique to measure and map optical losses across high-reflectivity supermirrors, revealing highly uniform coatings with minimal loss variations.

## Contribution

It presents a novel cavity ringdown method for spatially resolving optical loss variations on supermirrors, correlating measurements with microscopy images for detailed characterization.

## Key findings

- Achieved sub-1 ppm loss variation in supermirror coatings
- Demonstrated high agreement between ringdown measurements and microscopy
- Mapped spatial uniformity of optical losses across mirror surfaces

## Abstract

A cavity ringdown system for probing the spatial variation of optical loss across high-reflectivity mirrors is described. This system is employed to examine substrate-transferred crystalline supermirrors and quantify the effect of manufacturing process imperfections. Excellent agreement is observed between the ringdown-generated spatial measurements and differential interference contrast microscopy images. A 2 mm diameter ringdown scan in the center of a crystalline supermirror reveals highly uniform coating properties with excess loss variations below 1 ppm.

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Source: https://tomesphere.com/paper/1903.09665