Electrooptic Fabry-Perot filter: development for the study of solar oscillations

Observations of nonradial solar oscillations require Doppler velocity measurement at many points over the photosphere with a velocity resolution better than 1 m/s. An attractive form of imaging spectrophotometer for such a task utilizes a thin, solid, electrically tunable Fabry-Perot interference filter or etalon made of an electrooptic material such as lithium niobate (LiNbO(3)). The problems to be overcome in producing such an etalon for an imaging spectrophotometer are discussed and practical solutions demonstrated on the basis of measurements made on prototype devices.