# Ramsey-Bord\'e matter-wave interferometry for laser frequency stabilization at $10^{-16}$ frequency instability and below

## TL;DR

This paper demonstrates Ramsey-Bordé atom interferometry achieving laser frequency stabilization with a fractional instability below 2×10⁻¹⁶ over 10 to 1000 seconds, surpassing previous thermal atomic systems.

## Contribution

The work introduces a high-performance laser stabilization method using Ramsey-Bordé interferometry with unprecedented stability levels.

## Key findings

- Achieved fractional frequency instability <2×10⁻¹⁶ for 10-1000s
- Produced 1.6 kHz linewidth interference fringes
- Surpassed previous thermal atomic system performance

## Abstract

We demonstrate Ramsey-Bord\'e (RB) atom interferometry for high performance laser stabilization with fractional frequency instability $<2 \times 10^{-16}$ for timescales between 10 and 1000s. The RB spectroscopy laser interrogates two counterpropagating $^{40}$Ca beams on the $^1$S$_0$ -- $^3$P$_1$ transition at 657 nm, yielding 1.6 kHz linewidth interference fringes. Fluorescence detection of the excited state population is performed on the (4s4p) $^3$P$_1$ -- (4p$^2$) $^3$P$_0$ transition at 431 nm. Minimal thermal shielding and no vibration isolation are used. These stability results surpass performance from other thermal atomic or molecular systems by one to two orders of magnitude, and further improvements look feasible.