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