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