Design and Fabrication of a 9 Telescopes Visible Beam Combiner by Ultrafast Laser Inscription, for the FIRST/SUBARU Instrument
Researchers
DOCTORAL CANDIDATE
Sebin Sebastian Xavier
SUPERVISORS
Guillermo Martin, Université Grenoble Alpes (UGA)
Simon Gross, Macquarie University (MQ)
Michael J Withford, Macquarie University (MQ)
Research Areas
Nonlinear Optics, Optoelectronics , Lasers, Astronomical instrumentation, Spectroscopy
Project Brief
Ground-based telescopes struggle with atmospheric distortions, which limit their ability to directly observe faint exoplanets next to bright stars, thus requiring interferometric techniques to separate their faint signals from the overwhelming stellar brightness. Astrophotonics transforms astronomical instrumentation by integrating photonic technologies into optical systems, enhancing interferometry and high-resolution imaging.
The Fibered Imager for a Single Telescope (FIRST) at Subaru Telescope uses optical interferometry through pupil remapping, thus improving angular resolution. However, free-space optical setups and fibre-based systems suffer from optical losses, crosstalk, and misalignment issues, limiting their efficiency. To address the limitations, we aim to develop a five-telescope(5T) beam combiner using Ultrafast Laser Inscription (ULI) to fabricate a photonic integrated circuit (PIC).
PICs allow for low-loss, high-precision light guiding, reducing crosstalk while improving stability and spatial filtering. Their compactness enables mass production and seamless integration with adaptive optics and detectors. This study optimises the 5T beam combiner’s design to enhance transmission efficiency and interferometric performance. By incorporating a PIC within FIRST/SUBARU, this research advances PIC-based astrophotonic beam combiners, paving the way for the next generation of compact interferometric instruments.
Research Objectives :
The main goal of this project is to develop a photonic integrated circuit (PIC) that efficiently combines light from five telescope beams while ensuring uniform phase and intensity distribution. The objectives are:
1) Designing a compact beam combiner optimized for five telescope inputs.
2) Fabricating integrated optical waveguides using ULI to achieve high-precision light propagation.
3) Optimizing the waveguide to ensure minimal losses and efficient beam combination, ideally achromatic.
4) Characterizing the performance of the fabricated beam combiner using a dedicated optical bench.