Research Article

General Relativity and Gravitation

, Volume 37, Issue 9, pp 1555-1574

First online:

Geometry, Sagnac ring lasers and twisted EM modes

  • Robin W. TuckerAffiliated withDepartment of Physics, Lancaster University Email author 
  • , David A. BurtonAffiliated withDepartment of Physics, Lancaster University
  • , Adam NobleAffiliated withDepartment of Physics, Lancaster University

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A new geometric approximation scheme, designed to solve the covariant Maxwell equations inside a rotating hollow slender conducting cavity (modelling a ring-laser) on a background spacetime, is constructed. It is shown that for well-defined conditions the electromagnetic spectrum splits into TE- and TM-type modes. 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.


Frenet torsion Cavity Sagnac beat frequency