Possibility of measuring displacement with sub-nanometre accuracy by ring laser operating in lock-in regime

Abstract

The intensity difference between counterpropagating waves in ring lasers with back-reflection waves from external mirrors is analysed to enable a highly accurate measurement of displacement to be obtained. The difference is expressed as a periodic function of the distances between the ring laser mirrors and their corresponding mirrors. The measurement accuracy attainable with the difference can be in the sub-nanometre range.