Abstract: A mirror for a ring laser gyroscope comprising a multi-layer dielectric stack and a layer having an optical thickness of a half wavelength so as to enhance absorption of s-polarized radiation relative to that of p-polarized radiation.

Abstract: A magneto-optical phase-modulating device comprising a magneto-optic layer (3) forming part of an optical stack and upon which, in use, light is incident and to which is applied a magnetic field, a layer of magnetic material (6) adjacent the magneto-optic layer (3), and at least two flat, low inductance conductors (9,12) connected in series and disposed one on either side of the layer of magnetic material (6), in use the conductors (9,12) having an electric current applied thereto to provide a magnetic field in the layer of magnetic material (6), which magnetic field is switchable between one direction and the opposite direction by reversing the current in the conductors (9,12) and is of a strength relative to that of the magnetic field applied to the magneto-optic layer (3) such that the latter field is also switched between said one direction and the opposite direction as the field associated with the layer of magnetic material (6) is switched.

Abstract: The invention provides a magneto-optical phase-modulating device employing either the transverse Kerr magneto-optic effect or the Faraday magneto-optic effect and embodying a magneto-optic layer (1) of a ferromagnetic or ferrimagnetic garnet type material which gives rise to an improved performance over known devices. Examples of the garnet type material which may be employed are a bismuth doped garnet, praseodymium and a garnet type material of the group known as orthoferrite materials.The invention finds particular application in laser gyroscopes.