Imaging interferometers for analysis of Thomson scattered spectra

Howard, J.*; Hatae, Takaki

Polarization interferometers have some potential efficiency advantages for imaging Thomson scattering spectral analysis. In this article we present a number of designs for high-efficiency imaging polarization interferometers for Thomson scattering spectral analysis. The use of high efficiency crystal polarizing beamsplitters (both displacement and angle) results in low-loss complementary passbands (no edge losses), simple imaging systems and wide field-of-view. The efficiency and relative merits of both multiple-filter and dispersive-type configurations are being assessed before installation on the JT-60U ruby-laser Thomson scattering system. Light is transferred from the viewing port via a linear array of optical fibre bundles which will be imaged through the interferometer onto the photocathode of an intensified CCD camera. Because of the broadband nature of the Thomson light, the optical delays required to Fourier analyze the spectrum are quite small. This leads to compact multi-color or dispersive systems based on combinations of Wollaston and Savart splitters and traditional waveplates.