Stable CW laser based on low thermal expansion ceramic cavity with 4.9 mHz/s frequency drift.

Isao Ito,Alissa Silva,Yohei Kobayashi,Takuma Nakamura

doi:10.1364/oe.25.026020

Abstract

We describe a CW laser stabilized to a low thermal expansion ceramic cavity which has a lower frequency drift rate than cavities based on ultralow-expansion glass (ULE), which are widely used as optical references. Two identical optical cavities with spacers of different material, ceramic and ULE, were assembled and the optical frequencies locked to each of these cavities were compared. The optical frequency drifts of both CW lasers were measured to within a precision of 10-11 in one second over the course of one year. The ceramic cavity had a long-term frequency drift rate of 4.9 mHz/s and the ULE cavity had one of 23 mHz/s.

Highlights

Ultra-stable and narrow-linewidth CW lasers are widely used in many applications, such as precision spectroscopy [1], atomic clocks [2], and tests of fundamental physics [3]
We describe a CW laser stabilized to a low thermal expansion ceramic cavity which has a lower frequency drift rate than cavities based on ultralow-expansion glass (ULE), which are widely used as optical references
Such a performance might be useful for multiple applications with stringent demands on the long-term stability, such as astro-comb calibrated spectrographs used in observatories

Summary

Introduction

Ultra-stable and narrow-linewidth CW lasers are widely used in many applications, such as precision spectroscopy [1], atomic clocks [2], and tests of fundamental physics [3]. The structure of conventional glass, like SiO2, spontaneously changes from an unstable amorphous structure to a stable crystal one [12,13] This material aging effect is called creep, or crystallization, and it limits the stability of ULE glass cavity stabilized CW lasers to ∆f / f ~10−9 in one year, with typical frequency drift values ranging from 20 mHz/sec [14] and 100 mHz/sec [13]. In terms of spacer material for optical reference cavities, low thermal expansion ceramics seem like good candidates as they enable ultra-low long-term stability at room temperature and Hz level linewidths. A precise comparison of the long-term drift of a cavity based on NEXCERA ceramic and ULE glass is necessary To this end, we have developed two almost identical high-finesse cavities with different spacer materials, NEXCERA and ULE.

The CW laser stabilized to the ceramic cavity

Discussion

Conclusion