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