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Multi-material fibers are a promising platform for integrating nanoscale structures into macroscale photonic systems due to their unique aspect ratio: fiber cores can be kilometers long and sub-micrometric in their cross-section simultaneously. We are introducing Very Large-Scale Integration for Fibers (or, in short, VLSI-Fi) – manufacturing of integrated photonic circuits in a fiber analogous to VLSI from the microelectronics realm. VLSI-Fi starts with a thermal draw of the 3D printed preform, defining the cross-sectional geometry of the fiber, followed by the axial patterning of the fiber cores into arrays of integrated devices using a material-selective spatially coherent capillary breakup1,2 . Additional control over the photonic and electronic properties of devices is accomplished through segregation-driven control of doping. The result is a fiber-embedded integrated photonic circuit with user-defined 3D architecture providing the desired functionality. We argue that the capillary breakup of a viscous thread, nonlinear and often chaotic, becomes predictable if the axial symmetry of the thread viscosity is broken. We found that the capillary breakup of semiconducting fiber cores initiated by feeding the fiber through a spot-like liquefaction zone results in deterministic photonic and optoelectronic structures, such as gratings and spherical resonators. As a proof of concept, we demonstrate a selective breakup of a silicon core in fiber with one silicon and one vanadium core into an array of spherical silicon resonators, with a vanadium electrode flanking those resonators for electrical tuning of their resonant frequencies. Such cascaded resonators are a nontrivial example of photonic circuitry implemented in fiber using a non-CMOS approach.
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