Focal-plane wavefront sensing with narrowband light using a short multi-mode fiber

Area of Science:

• Optical Engineering
• Adaptive Optics
• Free-space Optical Communication

Background:

• Traditional wavefront sensors can suffer from non-common-path aberrations and sign ambiguities.
• Existing methods may not be suitable for real-time applications due to speed or complexity.
• Accurate wavefront sensing is crucial for improving performance in optical systems.

Purpose of the Study:

• To propose and demonstrate a novel focal-plane wavefront sensor (FPWFS) utilizing a short multimode fiber (MMF).
• To enable simultaneous wavefront and focal-plane intensity retrieval, eliminating non-common-path aberrations.
• To provide a compact, low-cost, and real-time solution for wavefront sensing.

Main Methods:

• Coupling aberrated focal-plane fields into a short (≲1 cm) multimode fiber.
• Preserving modal interference over a 10 nm bandwidth at near-infrared wavelengths.
• Utilizing a neural network for wavefront recovery from the fiber's output intensity pattern.

Main Results:

• Successfully encoded pupil phase information in the output intensity pattern.
• Resolved the sign ambiguity inherent in even pupil-phase aberrations.
• Achieved millisecond timescale operation using standard computing hardware.

Conclusions:

• The proposed MMF-based FPWFS offers a simple, compact, and cost-effective solution for adaptive optics.
• Its ability to eliminate non-common-path aberrations makes it ideal for shared optical paths.
• The technology is well-suited for applications in free-space optical communication and astronomical instrumentation.