| 摘要 |
The object of the invention is a phase modulator system (20) comprising a beam splitter and a reflection mode phase modulator (8) suitable for modula ting linearly polarised light of at least one specific polarisation state wh ile maintaining said polarisation state. The beam splitter and the phase mod ulator (8) are arranged along an optical path of a light beam (1, 3, 5, 7, 9 , 10, 11, 12). The beam splitter is a polarisation beam splitter (2) and the phase modulator system (20) further comprises an optical rotator (6) being arranged along the optical path between the polarisation beam splitter (2) a nd the phase modulator (8), and rotating the polarisation state of the light beam (5, 9) by 45° in a given sense, wherein the polarisation state of the light beam (7) incident upon the phase modulator (8) corresponds to said spe cific polarisation state. The invention further relates to a method for sepa rating an input light beam from a phase modulated light beam in a phase modu lator system comprising a phase modulator operable in reflection mode and su itable for modulating linearly polarised light of at least one specific line ar polarisation state while maintaining said specific linear polarisation st ate. The method comprises the steps of a) providing a light beam having a fi rst polarisation state by making an input lightbeam pass through a polarisat ion beam splitter; b) rotating said first polarisation state of said light b eam by 45° in a first sense by an optical rotator; c) reflecting said light beam by the phase modulator to obtain a phase modulated reflected light beam , wherein the polarisation state of the light beam incident upon the phase m odulator corresponds to said specific polarisation state; d) rotating the po larisation state of the reflected light beam by 45° in said first sense by t he optical rotator to obtain a light beam having a polarisation state orthog onal to said first polarisation state; and e) separating said light beam hav ing said second polarisation state from the input light beam by making the l ight beam pass through said polarisation beam splitter.
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