Liu_OE_17_21897_2009: http://dx.doi.org/10.1364/OE.17.021897
	Extremely basic binary grating of silicon square rods surrounded by air.
Bi_OE_18_11969_2010: http://dx.doi.org/10.1364/OE.18.011969
	Design of polarization splitting beam splitters by etching into fused silica.
Pietarinen_OE_14_2583_2006: http://dx.doi.org/10.1364/OE.14.002583
	Diffraction efficiency of multi-step transmission grating.
Oliva_OE_19_14735_2011: http://dx.doi.org/10.1364/OE.19.014735
	Diffraction efficiency of multi-step transmission grating.
