The system 7, wherein {TAIL ~ the first and second diffractive structures} are on {HEAD ~ a same surface} 
The system 7 , wherein { TAIL ~ the first and second diffractive structures } are on { HEAD ~ a same surface }
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD