Exoplanetary Systems Photonic Interferometric Combiner (ESPIC)

• Applicant: Professor Dr. Lucas Labadie
• Subject Area: Astrophysics and Astronomy ; Microsystems
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568980388

In the last decades, significant progress has been achieved in the identification of more than 5000 exoplanets. When benchmarked to our Solar System, the known extrasolar planetary systems show a large diversity in their demographics and properties. The next frontier of exoplanet science is thus to understand how unique or common Earth-analogs could be in our galactic neighbourhood by searching for bio-signatures such as O2, CO2, CH4, H2O in their atmosphere, which is ultimately linked to the quest of life in the Universe. To do so, the analysis of atmospheric spectra is an ideal way to deciphering the spectrum of an Earth-like planet in the habitable zone of a Sun-like star. In this context, the mid-infrared (MIR) range, between 3 and 20 µm, is particularly interesting as any molecules present specific absorption lines in this wavelength range. To detect the photons of the faint planet and separate them from those of their close and bright parent star, high-angular resolution and high-contrast techniques using multi-telescope nulling interferometry are required. The core engine of an interferometer is the beam combination unit, for which the benefit of photonic-based devices has been demonstrated at the Very Large Telescope Interferometer (VLTI). While most of the integrated optics (or photonics) technology has been driven by telecommunication applications around 1.5 µm, there is a growing research area targeting to extend operation of photonic circuits towards the mid-infrared range (MIR), especially for application in spectroscopy.Silicon Germanium (SiGe) SiGe-based on-chip interferometers have thus recently been developed in the 8 µm wavelength range. In this context, the ESPIC project will develop a new concept of integrated optics four-telescope interferometric beam combiner. ESPIC brings several innovations: 1) it opens the 3-13 µm MIR range in astrophotonics by leveraging the recent progress in SiGe mid-infrared photonics ; 2) it enables different combination schemes for self-calibration of the signal thanks to natural phase properties of couplers and MMI, and not at reach with classical bulk optics; 3) it integrates a unique on-chip phase control capability to precisely tune the phase difference which is a critical aspect for high-contrast techniques; 4) the instrument can be integrated in a cryogenic environment to minimize the impact of the thermal background. The connection to existing nulling interferometry projects such as NOTT/VLTI from the ground and the LIFE mission from space devoted to exoplanet spectroscopy is essential and timely since these are the main areas of application for the ESPIC outcome. With the synergy between the C2N in Palaiseau and the Institute of Astrophysics of Cologne, we combine unique and recognized competencies in the areas of mid-infrared photonics, and of instrumentation for astronomical long-baseline interferometry, ideally supported by a dense network of international collaboration.

• DFG Programme: Research Grants
• International Connection: France
• Major Instrumentation: Infrared camera 10 microns
• Instrumentation Group: 8620 Strahlungsthermometer, Pyrometer, Thermosonden
• Cooperation Partner: Professorin Dr. Delphine Marris-Morini