Tri-coupler geometries for achromatic nulling interferometry in the near-infrared
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arXiv
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| Autori principali: | , , , , , , |
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| Natura: | Preprint |
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2026
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| author | Goldsmith, Harry-Dean Kenchington Jovanovic, Nemanja Asnodkar, Anusha Pai Kim, Yoo Jung Sanny, Ahmed Gatkine, Pradip Fitzgerald, Michael P. |
| author_facet | Goldsmith, Harry-Dean Kenchington Jovanovic, Nemanja Asnodkar, Anusha Pai Kim, Yoo Jung Sanny, Ahmed Gatkine, Pradip Fitzgerald, Michael P. |
| contents | Astrophotonics is central to the next generation of astronomical instrumentation, enabling compact photonic integrated circuits for both ground-based observatories and future space missions. Beam combination for nulling interferometry suppresses starlight, revealing exoplanets and companions.
Two-waveguide photonic combiners rely on symmetric evanescent, inherently chromatic, coupling to interfere light. A three-waveguide configuration, or tri-coupler, offers the potential for deeper, broader, and more stable achromatic nulls compared with two-waveguide approaches. This work compares the simulated performance of evanescent tri-couplers and a multimode interference coupler across the 1.5-1.8 micron band, evaluating exoplanet throughput, starlight attenuation, sensing characteristics, and estimations on fabrication tolerance. All three tri-couplers achieved >40dB attenuation over a 270nm bandwidth. Including component loss, the tapered tri-coupler has the highest total throughput, averaging 97%, whereas the standard tri-coupler began with an equivalent exoplanet throughput and fell to 50% at the band edges. The tapered tri-coupler was further redesigned to achieve a non-degenerate sensing state. The MMI, while limited to a starlight attenuation of 40dB by uncoupled light, showed the greatest tolerance to fabrication errors.
Future designs aim to combine high exoplanet throughput, deep starlight attenuation, and non-degenerate sensing within a single integrated architecture. This work provides a simulation suite for three tri-couplers. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_23693 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Tri-coupler geometries for achromatic nulling interferometry in the near-infrared Goldsmith, Harry-Dean Kenchington Jovanovic, Nemanja Asnodkar, Anusha Pai Kim, Yoo Jung Sanny, Ahmed Gatkine, Pradip Fitzgerald, Michael P. Instrumentation and Methods for Astrophysics Earth and Planetary Astrophysics Astrophotonics is central to the next generation of astronomical instrumentation, enabling compact photonic integrated circuits for both ground-based observatories and future space missions. Beam combination for nulling interferometry suppresses starlight, revealing exoplanets and companions. Two-waveguide photonic combiners rely on symmetric evanescent, inherently chromatic, coupling to interfere light. A three-waveguide configuration, or tri-coupler, offers the potential for deeper, broader, and more stable achromatic nulls compared with two-waveguide approaches. This work compares the simulated performance of evanescent tri-couplers and a multimode interference coupler across the 1.5-1.8 micron band, evaluating exoplanet throughput, starlight attenuation, sensing characteristics, and estimations on fabrication tolerance. All three tri-couplers achieved >40dB attenuation over a 270nm bandwidth. Including component loss, the tapered tri-coupler has the highest total throughput, averaging 97%, whereas the standard tri-coupler began with an equivalent exoplanet throughput and fell to 50% at the band edges. The tapered tri-coupler was further redesigned to achieve a non-degenerate sensing state. The MMI, while limited to a starlight attenuation of 40dB by uncoupled light, showed the greatest tolerance to fabrication errors. Future designs aim to combine high exoplanet throughput, deep starlight attenuation, and non-degenerate sensing within a single integrated architecture. This work provides a simulation suite for three tri-couplers. |
| title | Tri-coupler geometries for achromatic nulling interferometry in the near-infrared |
| topic | Instrumentation and Methods for Astrophysics Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2602.23693 |