Technology for creating a photonic integrated circuit on a lithium niobate substrate

We propose a new technology for manufacturing a photonic integrated circuit (PIC) on a lithium niobate substrate. It is shown that there is no need to dope the top layer of lithium niobate to create a waveguide system and control radiation. It will suffice to coat the lithium niobate substrate with a layer of a material with higher refractive index, thus creating an asymmetric waveguide, with the radiation mainly propagating deeper within the lithium niobate. In this way, placing metal electrodes along the waveguide layer, it is possible to control the velocity of wave propagation in a waveguide and create controlled photonic circuits, for example, an amplitude Mach-Zehnder modulator or a phase modulator. A technology of spraying a titanium dioxide layer onto the lithium niobate substrate is experimentally created and investigated. It is shown that after the finishing polishing of the end side of the lithium niobate plate, radiation exits from the plate output end. So, it becomes possible to create a PIC with an array of closely spaced waveguides, from which radiation can be output into space and coupled into the lens of a photo or video camera for further processing.