Integrated broadband bent directional coupler for use in telescope interferometry in the visible (600 nm – 820 nm)

Giannis Poulopoulos; Georgios Syriopoulos; Evrydiki Kyriazi; Thenia Prousalidi; Dimitris Apostolopoulos; Xavier Haubois; Charalampos Zervos; Hercules Avramopoulos

doi:10.1117/12.3001472

8 March 2024 Integrated broadband bent directional coupler for use in telescope interferometry in the visible (600 nm – 820 nm)

Giannis Poulopoulos, Georgios Syriopoulos, Evrydiki Kyriazi, Thenia Prousalidi, Dimitris Apostolopoulos, Xavier Haubois, Charalampos Zervos, Hercules Avramopoulos

Author Affiliations +

Proceedings Volume 12882, Optical Components and Materials XXI; 128820T (2024) https://doi.org/10.1117/12.3001472
Event: SPIE OPTO, 2024, San Francisco, California, United States

Conference Poster

Abstract

Very Large Telescope Interferometers (VLTI) are based on interferometry to combine the light collected by more than one telescopes (such as ESO’s telescopes combining light collected by four 8.2-metre Telescopes), enabling the observation of new phenomena, opening up new research areas. The light beams are brought together using a complex system of free space components based on pairwise combination utilising the ABCD scheme. Currently bulky free space optics, with complex and very voluminous setups (10 beam input results in 180 outputs), are too sensitive to operate in ambient, while require the path difference must be kept in sub-millimetre scale. Photonic Integrated Circuits (PIC) advantages of miniaturization, stability, and precise active phase control, make them good candidates to develop the beam combining circuits. Key elements towards realization of these circuits are power splitters, low-loss crossings and directional couplers, all operating in a wide range of wavelengths (600 nm – 820 nm). However, the splitting ratio of conventional directional couplers is very sensitive to wavelength, which limits the bandwidth and the transmission performance of the devices. In this paper, we present the design methodology on a low-loss, broadband, and large fabrication tolerance, bend directional coupler realised on Silicon Nitride integration platform. FDE simulation tool was employed for waveguide modes and coupled system supermodes calculation, 2D-FDTD for propagation simulations, while the results were verified via 3D-FDTD simulations. The proposed bend directional coupler enhances conventional couplers performance, achieving splitting ratio of +-10% around target splitting value for the whole 220 nm target wavelength range, for a footprint of 100 μm x 20 μm.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Giannis Poulopoulos, Georgios Syriopoulos, Evrydiki Kyriazi, Thenia Prousalidi, Dimitris Apostolopoulos, Xavier Haubois, Charalampos Zervos, and Hercules Avramopoulos "Integrated broadband bent directional coupler for use in telescope interferometry in the visible (600 nm – 820 nm)", Proc. SPIE 12882, Optical Components and Materials XXI, 128820T (8 March 2024); https://doi.org/10.1117/12.3001472

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