a substrate on which {HEAD ~ a surface acoustic wave propagation region} for guiding a surface acoustic wave and an optical waveguide for guiding {TAIL ~ an optical wave} are provided; and 
a substrate on which { HEAD ~ a surface acoustic wave propagation region } for guiding a surface acoustic wave and an optical waveguide for guiding { TAIL ~ an optical wave } are provided ; and
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH