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