Importance

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Abstract

A photodetector device comprising a photosensitive detector (12; 96) and one or more interfaces (20', 20', 28, 98) between dissimilar media is configured so that a light beam (LB) for detection will pass through the interface(s) along a beam axis that is not normal to the interface(s). The deviation (.theta.) from the normal will be such that polarization dependent transmission introduced at the interface(s) will compensate for inherent polarization dependency of the detector (12; 96). The deviation may be achieved by inclining the interface(s) relative to a predetermined direction along which the light beam will be incident. Where the photosensitive detector is in a housing (84) with a window (20) through which the light beam enters the housing, the housing can be tilted. In such as case, there are three interfaces, one (28; 98) at the surface of the detector (12; 96), and one at each surface (20', 20') of the window (20). Alternatively, the detector surface and/or the window could be tilted. Where a pigtail fiber (116) is permanently attached to the photodetector device to input the light beam through an interposed lens (106), the end of the pigtail fiber may be offset laterally from the lens optical axis (LOA) so that the beam axis deviates from the normal by such an angle that the resulting polarization dependent transmission (PDT) substantially corrects for polarization dependent response (PDR) of the photosensitive detector. An end facet of the pigtail fiber, the lens, and/or the window may be inclined so that they are not perpendicular to the propagation direction of the light beam so as to reduce interference and backreflection effects.

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First Claim