Crystallization in Zirconia Film Nano-Layered with Silica.

Brecken Larsen,Gilberto Desalvo,Christopher Ausbeck,Marina Mondin,Riccardo Desalvo,Timothy F Bennet,Tugdual Lebohec,Joshua Neilson,Seth Linker

doi:10.3390/nano11123444

Abstract

Gravitational waves are detected using resonant optical cavity interferometers. The mirror coatings’ inherent thermal noise and photon scattering limit sensitivity. Crystals within the reflective coating may be responsible for either or both noise sources. In this study, we explored crystallization reduction in zirconia through nano-layering with silica. We used X-ray diffraction (XRD) to monitor crystal growth between successive annealing cycles. We observed crystal formation at higher temperatures in thinner zirconia layers, indicating that silica is a successful inhibitor of crystal growth. However, the thinnest barriers break down at high temperatures, thus allowing crystal growth beyond each nano-layer. In addition, in samples with thicker zirconia layers, we observe that crystallization saturates with a significant portion of amorphous material remaining.

Highlights

The Laser Interferometer Gravitational-Wave Observatory (LIGO) [1], Virgo [2], KamiokaGravitational-Wave Detector (KAGRA) [3] and GEO600 [4] gravitational wave detectors perform some of the most precise interferometric measurements across a wide band of frequencies [5]
We report on a study of zirconia nano-layered with silica characterizing crystal formation in the course of annealing cycles
We observed that the zirconia crystallization temperature increases from ∼370 ◦ C to above 800 ◦ C with increasing segmentation, indicating that, as expected, nano-layering suppresses crystal formation, in zirconia segmented by silica

Summary

Introduction

The Laser Interferometer Gravitational-Wave Observatory (LIGO) [1], Virgo [2], KamiokaGravitational-Wave Detector (KAGRA) [3] and GEO600 [4] gravitational wave detectors perform some of the most precise interferometric measurements across a wide band of frequencies [5]. Millions of sub-wavelength-sized objects within dielectric coating layers scatter a few parts per million of the interferometer’s laser light power. We can observe these objects through the off-axis imagining of the end test mass coating surfaces illuminated by the Fabry Perot stored beams [9]. The light scattered out of the interferometer reduces the circulating power and degrades the squeezed vacuum performance [10]. If this light was lost, it would amount to a relatively modest noise contribution. Even a modest reduction in scattering could be significant as it can enter twice in the phase noise generation process

Methods

Results

Conclusion