The grating can have {HEAD ~ a periodicity} from {TAIL ~ 200 nm} to 500 nm 
from
The grating can have { HEAD ~ a periodicity } from { TAIL ~ 200 nm } to 500 nm
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH