Patent ID: 7336323
Filing Date: 2008-02-26
Classification: G02B,G02F

Abstract:
1. A spectral band stop filter, comprising: at least one selection polarizer and a plurality of tunable birefringence elements coupled along a signal propagation path leading from an input up to the selection polarizer, wherein each of the birefringence elements in the plurality has a birefringence and a rotational orientation that complements a respective birefringence and rotational orientation of the remaining birefringence elements in said plurality, in that each of the birefringence elements contributes part of a change in a polarization state between the input and the selection polarizer for a set of periodically related wavelengths, thereby imparting a predetermined polarization orientation to a component with a given orientation at the input and a wavelength in the set of periodically related wavelengths, said predetermined polarization orientation being different from an orientation of other wavelengths; wherein the selection polarizer is oriented orthogonal to said predetermined polarization orientation, thereby blocking transmission of a band discrimination wavelength at the selection polarizer and permitting the other wavelengths to be transmitted by the selection polarizer; and, further comprising a control operable to tune the birefringence elements so as to adjust the set of periodically related wavelengths, such that the band discrimination wavelength is tunable by causing one of the periodically related wavelengths to correspond to a selected wavelength to be blocked.