Programmable waveguides scalable into highly integrated photonic circuits are key ingredients to the development of innovative optical technology in various rapidly growing fields, including linear quantum computation and optical information processing [1-3]. At present, no scalable optical writing technique based solely on linear waves has been demonstrated in a full macroscopic volume and circuit fabrication involves a step-by-step printing that becomes increasingly cumbersome as design complexity grows. We demonstrate a scalable method to optically induce waveguides deep in a volume using Bessel beams . The method is used to fabricate waveguides in increasingly complex geometries, integrated multi-port splitters and miniaturized functional electro-optic gates. Our experiments are performed in paraelectric potassium-lithium-tantalate-niobate (KLTN) where writing occurs through photogenerated space-charge while guiding and electro-optic functionality are supported by the quadratic electro-optic effect. In Fig. 1 we demonstrate the use of Bessel Beam (BB) waveguide writing to achieve 1×2, 1×3, and 1×4 splitters launching multiple angled BBs during the fabrication stage. The BBs are rendered mutually incoherent using a specific SLM time sequenced mask that turns on one BB at a time. This demonstrates how fabrication of complex circuitry can also be achieved in a single illumination stage without having to mechanically shift and move the sample, as instead is required in direct writing scanning techniques.
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