Reduction of polarization-dependent loss in double-pass grating configurations
View Patent ↗Optical systems for routing light that reduce or eliminate polarization-dependent loss are provided. Such optical systems generally accommodate an optical element that has an intrinsic polarization-dependent loss and which is disposed to be encountered twice by the light being routed. In some instances, the optical element may be a dispersive element such as a diffraction grating or prism, but the invention has more general applicability. The optical system additionally includes both a reflective element and a wave plate assembly disposed to be encountered by the light between encounters with the dispersive element.
1. An optical system for routing light, the optical system comprising:
an optical element having an intrinsic polarization-dependent loss and disposed to be encountered by the light at least twice;
a reflective element disposed to be encountered by the light between encounters with the optical element; and
a wave plate disposed to be encountered by the light between encounters with the optical element, wherein the wave plate has a retardance optimized according to a material property of the reflective element to reduce polarization-dependent loss in the system and/or the wave plate has an orientation optimized according to a material property of the reflective element to reduce polarization-dependent loss in the optical system,
wherein:
the light comprises a plurality of spectral bands;
the optical element comprises a dispersive element; and
the reflective element comprises a plurality of dynamically configurable routing elements to direct given spectral bands depending on a state of each such dynamically configurable routing element.
2. An optical system for routing light, the optical system comprising:
an optical element having an intrinsic polarization-dependent loss disposed to be encountered by the light at least twice along an optical path;
a reflective element disposed to be encountered by the light between encounters with the optical element; and
a wave plate disposed to be encountered by the light exactly once between encounters with the optical element,
wherein:
the reflective element comprises an even number of reflective surfaces disposed to be encountered by the light; and
the wave plate comprises a half-wave plate having a fast axis oriented with respect to dichroic axes of the optical element at substantially an odd multiple of 45° .