The invention provides a preparation method of an electro-optical
crystal thin film, the electro-optical
crystal thin film and an electro-
optical modulator, and the preparation method of the electro-optical
crystal thin film comprises the following steps: preparing a
silicon-on-insulator structure, and preparing a protective layer precursor on top
silicon of the
silicon-on-insulator structure;
etching the protective layer precursor and the top silicon layer by using an
etching method to form a protective layer and a silicon
waveguide layer, forming a groove structure in the protective layer and the silicon
waveguide layer after
etching, and enabling the height of the groove structure to be equal to the sum of the thickness of the protective layer and the thickness of the silicon waveguidelayer; filling and
coating an
isolation layer in the groove structure, and flattening the
isolation layer until the
isolation layer is flush with the
protection layer; removing the protective layer ina
corrosion manner, depositing and
coating the isolation layer, and flattening the isolation layer; and finally, preparing a functional film layer on the
coating isolation layer to obtain the electro-optic crystal film. By adopting the scheme, the silicon
waveguide layer is protected by the protective layer, the thickness of the coated isolation layer is controllable, the surface is smooth, the coated isolation layer is bonded with the functional film layer, and the propagation of optical signals is not influenced.