Spatial light shaping of uniform femtosecond laser filament for fabrication of Bragg grating arrays in optical fibers

Direct laser writing, combined with beam shaping techniques, enables the integration of compact photonic components essential for applications such as ultrasmall filters, photonic chips, and quantum information processing. This presentation describes the assembly of laser-written, uniform, void filaments into two-dimensional photonic crystals to provide strong and compact grating functions for propagating light in optical fibers. A novel Bessel beam generation scheme with algorithm-guided intensity shaping along the filament axis was designed to control energy deposition. The efficiency of fiber Bragg grating filters and fiber spectrometers were evaluated over varying filament parameters and photonic crystal designs, demonstrating their efficacy for generating more compact photonic filtering functions due to the high refractive index contrast of the open capillary nanostructure.