Stable deep nulling in polychromatic unpolarized light with multiaxial beam combination

Area of Science:

• * Astronomy and astrophysics
• * Optical interferometry
• * Space-based observatories

Background:

• * The European Space Agency (ESA) Darwin mission aims for space-based nulling. Thales Alenia Space developed the multiaperture imaging interferometer (MAII) breadboard for ESA to demonstrate deep and stable nulling.
• * Investigations extended to multiaxial beam combination, offering simplicity, compactness, and high coupling efficiency for three-beam combinations.

Purpose of the Study:

• * To demonstrate deep and stable nulling using the MAII breadboard.
• * To investigate subsystems of the ESA Darwin interferometer.
• * To evaluate the multiaxial beam combination scheme for space-based nulling.

Main Methods:

• * Upgraded the near-infrared (λ ≈ 1.55 μm) MAII breadboard to a multiaxial beam combination configuration.
• * Investigated polarization and stability issues within the multiaxial setup.
• * Conducted experiments with unpolarized light and a relative spectral bandwidth of 5%.

Main Results:

• * Achieved mean nulling ratios (N) of 1.7 x 10⁻⁵.
• * Demonstrated stability of nulling over 1 hour with a standard deviation (σ(N)) of 5.7 x 10⁻⁷.
• * Validated performance in unpolarized light with a 5% relative spectral bandwidth.

Conclusions:

• * The multiaxial beam combination is a promising technique for space-based nulling.
• * The MAII breadboard's performance meets the stringent requirements of the ESA Darwin mission.
• * This approach offers a viable path for future high-contrast imaging missions.