For example, {TAIL ~ the maximum gain} can occur at {HEAD ~ an energy} at or below the maximum band gap emission 
For example , { TAIL ~ the maximum gain } can occur at { HEAD ~ an energy } at or below the maximum band gap emission
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH