Commissioning the AIP's ultrafast laser Inscription facility: defining the parameter space for type-I waveguide fabrication

RESUMO

Astrophotonics offers a compact, stable alternative to bulk optics in traditional astronomical instrumentation, spanning high-precision spectroscopy to high-contrast interferometry. However, the strict requirements for throughput, accuracy, precision, and stability require tailored manufacturing processes that go beyond standard telecommunications technology. This work presents the iterative experimental and statistical methods used to determine the optimal laser-writing conditions for passive waveguides in silica glass using a femtosecond laser inscription setup. We systematically explored the parameter space by varying pulse energy, repetition rate, translation speed, and scan numbers to identify the optimal conditions for Type-1 waveguides, characterized by a positive refractive-index modification in their cores. We report on the refinement of these parameters to manufacture single-mode, high-throughput waveguides that operate in the astronomical J-band (1300-1400 nm). A key focus of this optimization is to match the mode field diameter (MFD) to the SMF28 fibre and minimize insertion losses. This development is critical for astrophotonics devices, such as photonic reformatters, beam combiners, and pupil remappers, as well as post-fabrication correction of phase errors in photonic components fabricated using traditional photolithographic methods. Some of these components will be used for future on-sky validation at the Calar Alto Observatory and the CHARA array.