The mode conversion means is provided in the substrate, in the light emitting layer, or at {HEAD ~ the interface} between the substrate and {TAIL ~ the light} emitting layer 
between
The mode conversion means is provided in the substrate , in the light emitting layer , or at { HEAD ~ the interface } between the substrate and { TAIL ~ the light } emitting layer
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH