Accousto-optic tunable filter.

摘要

An acousto-optic tunable filter, for laser tuning, comprises an acoustic transducer (13) connected to one face of an anisotropic crystal (9) or Bragg cell which is cut at such an angle relative to its optic axis that an acoustic wave projected into the crystal normal to the said face causes wavelength-specific diffraction of an incident optic wave (from laser amplifying element 2) which nearly, but not completely, satisfies the parallel-tangents phase matching condition, thus preserving a substantial angular field of view, the said angle also being such that the said diffraction is polarisation-insensitive.