Photonic chip for visible interferometry: laboratory characterization and comparison with the theoretical model

TL;DR

This paper reports on the development and laboratory testing of a photonic integrated circuit for visible interferometry, aiming to enhance astronomical measurements at the H-alpha line with improved stability and sensitivity.

Contribution

It introduces a novel PIC design for visible interferometry, including waveguide characterization and simulation of key interferometric components.

Findings

Waveguides are characterized with specific mode properties.

Simulations show potential for achromatic couplers and phase shifters.

The work advances integrated optics for astronomical interferometry.

Abstract

Integrated optics are used to achieve astronomical interferometry inside robust and compact materials, improving the instruments stability and sensitivity. In order to perform differential phase measurements at the H$\alpha$ line (656.3 nm) with the 600-800 nm spectro-interferometer FIRST, a photonic integrated circuit (PIC) is being developed. This PIC performs the visible combination of the beams coming from the telescope pupil sub-apertures. In this work, TEEM Photonics waveguides fabricated by $K_+:Na_+$ ion exchange in glass are characterized in terms of single-mode range and mode field diameter. The waveguide diffused index profile is modeled on Beamprop software. FIRST beam combiner building blocks are simulated, especially achromatic directional couplers and passive $\pi/2$ phase shifters for a potential ABCD interferometric combination.