TE/TM-Modenkonverter

The invention relates to a TE/TM mode converter. The mode converter consists of a substrate (1) made of lithium niobate comprising a single-mode optical waveguide (3) which extends between two end faces (4, 5) of the substrate (1) along its surface, and having an electro-acoustic transducer (8) arranged on the surface (2), by means of which acoustic surface waves running co-linearly to the longitudinal axis of the waverguide (3) can be generated. The mode converter also has a stripline layer (9) consisting of proton-exchanged lithium niobate, said layer covering the optical waveguide (3) at its top boundary surface (6) facing the substrate surface (2), at least in an area arranged after the electro-acoustic transducer (8). The proton-exchanged layer (9) according to the invention is formed at least to such a depth so as to ensure that the extraordinary mode is guided in the proton-exchanged area of the waveguide (3). With such a layer (9), it is possible to shift the necessary acoustic conversion frequency definitively by at least 15 to 20 MHz.