Fresnel rhombs as achromatic phase shifters for infrared nulling interferometry

Area of Science:

• Optics and Photonics
• Astronomy Instrumentation

Background:

• Infrared nulling interferometry requires precise phase control for high-contrast imaging.
• Achieving achromatic phase shifts over broad bandwidths is a significant challenge in optical component design.

Purpose of the Study:

• To introduce a novel family of achromatic phase shifters for infrared nulling interferometry.
• To enable precise vectorial phase shifts for destructive interference in interferometers.
• To compensate for material dispersion for broadband achromatic performance.

Main Methods:

• Utilizing the phenomenon of total internal reflection (TIR) in optimized Fresnel rhomb designs.
• Modulating the refractive index transition at the TIR interface using thin films or subwavelength gratings.
• Conducting theoretical simulations and preliminary experimental validation with a Zinc Selenide prototype.

Main Results:

• Demonstrated a method for inducing wavelength-independent phase shifts using modulated TIR.
• Theoretical simulations show broadband achromatic performance.
• Preliminary fabrication and measurements confirm prototype functionality.

Conclusions:

• The proposed achromatic phase shifters offer a promising solution for advanced infrared nulling interferometry.
• Modulated TIR provides a viable pathway to overcome chromatic dispersion limitations in optical components.
• Further development could enhance capabilities for astronomical observations of exoplanets and other faint objects.