Echelle gratings with low polarization dependent loss ( PDL) using metal coating on the reflecting facets only

摘要

An Echelle grating has alternate first ( 1 a) and second ( 1 b) sets of facets ( 1 ). The first set of facets ( 1 a) is operative to reflect incident light ( 4 ) for diffraction and the second set of facets ( 1 b) extends between adjacent facets of the first set ( 1 a). Only the first set of facets ( 1 a) is metallized to enhance reflection. The second set of facets ( 1 b) is left unmetallized. This configuration reduces polarization dependent loss (PDL).