Mechanical loss and stability analysis of NEXCERA in ultra-stable optical cavities

TL;DR

This study measures the mechanical loss of NEXCERA ceramic, demonstrating its low thermal noise potential for ultra-stable optical cavities, and compares its performance with other materials like ULE and Zerodur.

Contribution

It provides the first mechanical loss measurement of NEXCERA at room temperature and evaluates its suitability for ultra-stable optical cavities.

Findings

NEXCERA exhibits a minimum mechanical loss of 1.89×10⁻⁵.

Thermal noise analysis shows NEXCERA outperforms some traditional materials.

NEXCERA's low linear drift enhances its appeal for frequency references.

Abstract

NEXCERA has emerged as a ceramic-based material for spacers in ultra-stable optical cavities, with a coefficient of thermal expansion that crosses zero near room temperature. In such cavities, frequency stability is ultimately limited by Brownian thermal noise in the cavity components. A key parameter in this context is the mechanical loss, which has remained unknown for NEXCERA. In this work, we investigate the mechanical loss of NEXCERA N117B at room temperature for various resonances using the gentle nodal suspension technique. We measure a promising minimum mechanical loss of $\phi = 1.89\times 10^{-5}$, indicating the suitability of NEXCERA for low-noise optical cavities. Using this value, we calculate the thermal noise of a cavity with a NEXCERA spacer and compare its performance to established materials such as ULE and Zerodur, taking into account different mirror substrate options. Our analysis shows that NEXCERA is a strong candidate for ultra-stable cavities due to its low thermal noise. Combined with its previously reported low linear drift, it offers a highly attractive option for long-term stable optical frequency references.