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Twisted electromagnetic modes and Sagnac ring lasers

Research output: Contribution to journalJournal article


<mark>Journal publication date</mark>21/03/2005
<mark>Journal</mark>Classical and Quantum Gravity
Issue number6
Number of pages23
Pages (from-to)909-931
<mark>Original language</mark>English


A new approximation scheme, designed to solve the covariant Maxwell equations inside a rotating hollow slender cavity (modelling a ring laser), is constructed. It is shown that for well-defined conditions there exist TE and TM modes with respect to the longitudinal axis of the cavity. A twisted mode spectrum is found to depend on the integrated Frenet torsion of the cavity and this in turn may affect the Sagnac beat frequency induced by a non-zero rotation of the cavity. The analysis is motivated by attempts to use ring lasers to measure terrestrial gravito-magnetism or the Lense–Thirring effect produced by the rotation of the earth.