Unlike conventional resonators, the guiding channel could be comprised of low index material or {HEAD ~ even air}, which can reduce significantly {TAIL ~ the material related loss} 
reduce significantly
Unlike conventional resonators , the guiding channel could be comprised of low index material or { HEAD ~ even air } , which can reduce significantly { TAIL ~ the material related loss }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL