Sparse intensity sampling for ultrafast full-field reconstruction in low-dimensional photonic systems

Area of Science:

• Optics and Photonics
• Quantum Information Science

Background:

• Phase-sensitive measurements traditionally rely on interferometry, which can be complex and slow.
• Existing intensity-only methods for optical field characterization are computationally intensive and require slow CCD cameras.

Purpose of the Study:

• To develop a computationally efficient, intensity-only method for full complex-valued optical field reconstruction.
• To enable high-speed, full-field characterization in low-dimensional systems without a reference beam.

Main Methods:

• Utilizing a few strategically placed photodetectors to capture intensity measurements.
• Reconstructing the complex-valued optical field from these intensity-only measurements in low-dimensional systems.
• Applying the method to few-mode fibers for mode amplitude and phase retrieval.

Main Results:

• Achieved full-field characterization using only intensity measurements, eliminating the need for interferometry or a reference beam.
• Demonstrated a method that is 3 orders of magnitude faster and uses 3 orders of magnitude fewer photodetectors than previous state-of-the-art techniques.
• Successfully retrieved mode amplitudes and phases relative to the fundamental mode.

Conclusions:

• The presented intensity-only method offers a significant advancement for ultrafast optical field characterization.
• This approach facilitates high-speed applications such as pulse-to-pulse laser beam characterization and spatiotemporal modelocked system analysis.
• Potential applications include ultrafast sensing in few-mode fibers and coherent mode division-multiplexed receivers.