Spectral beam combining gratings: high diffraction efficiency at a large deviation angle achieved around conical Littrow mounting.

We theoretically make plausible and numerically verify that when a high-efficiency, polarization-independent grating, designed to work at or near Littrow mounting, is used in conical Littrow mounting, its high efficiency and polarization independence can be very well maintained at a large off-principal-plane deviation angle. This finding provides a new degree of freedom to the design of high-efficiency, more compact spectral beam combining grating systems.