High-order achromatic quarterwave combination plates and tuners.
Achromatic quarterwave combination plates are formed from two high-order birefringent plates having even and odd multiples of quarterwave retardation at some nominal wavelength. Eleventh- and twelfth-order plates at 1315 nm combined with their axes 77 degrees apart are shown to have 90 +/- 0.25 degrees of retardation between 1275 and 1355 nm. They can be used to construct two- and four-waveplate tuners for birefringent filters.
Buhrer
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CF