Optical steering of a large ring laser

TL;DR

This paper introduces a method to stabilize the mode operation of a large ring laser by using optical steering via injection locking, ensuring reliable mode selection crucial for precision applications.

Contribution

The authors demonstrate a novel optical steering technique that stabilizes the mode of a large ring laser through injection locking, improving its suitability for metrological use.

Findings

Injected mode reliably follows external steering

Counter-propagating mode can also follow due to backscattering

Method enables stable operation on a chosen mode

Abstract

A common approach to reduce the linewidth of a laser is an increase of its resonator length. In large gas lasers, however, the frequency spacing between longitudinal modes of the resonator easily becomes significantly smaller than the Doppler-broadened width of the gain profile. As a consequence, the laser might operate on a multitude of modes simultaneously, or jump between modes. Such unstable operation cannot be tolerated in metrological or sensing applications, such as ring laser gyroscopes. Here, we propose and demonstrate a method to establish stable operation on a chosen mode index by optically steering the ring laser to a desired mode index through injection locking with an external laser. The injected mode reliably follows the external steering. Intra-cavity backscattering can even cause the counter-propagating, non-injected mode to follow the external steering as well.