The invention discloses an SOI (
silicon on insulator) based electrooptical modulator based on symmetrical and vertical
grating coupling, which comprises a symmetrical and vertical
coupling grating, a 3-d B
optical beam splitter, two mode
converters, two optical phase shift arms, an
optical beam combiner, two
coplanar waveguide wave traveling electrodes and an annular
metal alignment mark, wherein the 3-d B
optical beam splitter acts as an interface of the SOI based electrooptical modulator and a single mode
fiber or an input end of a coupler and the SOI based electrooptical modulator; the two mode
converters act as the connection of a wide wave guide of the symmetrical and vertical
coupling grating and a single mode
ridge-shaped
waveguide; each optical phase shift arm consists of the single mode
ridge-shaped
waveguide and an electric structure embedded into the single mode
ridge-shaped
waveguide; the optical beam combiner is used for combining the light in the two optical phase shift arms which are divided by the symmetrical and vertical coupling grating into one beam, thus
phase modulation of light is converted into
intensity modulation; the
coplanar waveguide wave traveling electrodes are respectively positioned on the two optical phase shift arms, form
electric contact with the electric structure in the optical phase shift arms, and are used for the loading and transmission of
radio frequency / micro wave electrical modulation signals; and the annular
metal alignment mark is positioned around the symmetrical and vertical coupling grating, and is used for the alignment of the
optical fiber in an optical grating test.