A high sensitivity tool for geophysical applications: A geometrically locked Ring Laser Gyroscope

TL;DR

This paper presents a middle-sized, geometrically locked ring laser gyroscope demonstrating high sensitivity and robustness for rotational seismology in noisy environments, with long-term stability of 3 nanorad/s and short-term sensitivity near 2 nanorad/s·Hz^{-1/2}.

Contribution

The work introduces a stable, locked square cavity RLG capable of operating effectively in noisy environments, with simple locking circuitry ensuring long-term stability for seismic applications.

Findings

Long-term stability of about 3 nanorad/s.

Short-term sensitivity close to 2 nanorad/s·Hz^{-1/2}.

Operates effectively in a noisy urban environment.

Abstract

This work demonstrates that a middle size ring laser gyroscope (RLG) can be a very sensitive and robust instrument for rotational seismology, even if it operates in a quite noisy environment. The RLG has a square cavity, $1.60\times 1.60$ m$^2$, and it lies in a plane orthogonal to the Earth rotational axis. The Fabry-Perot optical cavities along the diagonals of the square were accessed and their lengths were locked to a reference laser. Through a quite simple locking circuit, we were able to keep the sensor fully operative for 14 days. The obtained long term stability is of the order of 3~nanorad/s and the short term sensitivity close is to 2~nanorad/s$\cdot$Hz$^{-1/2}$. These results are limited only by the noisy environment, our laboratory is located in a building downtown.