In this instance, {HEAD ~ a buffer layer} for preventing {TAIL ~ propagation loss} of the optical waves in the excitation electrode may be formed between the substrate and the excitation electrode 
for preventing
In this instance , { HEAD ~ a buffer layer } for preventing { TAIL ~ propagation loss } of the optical waves in the excitation electrode may be formed between the substrate and the excitation electrode
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH