Metasurface Enhanced Spatial Mode Decomposition

TL;DR

This paper demonstrates a metasurface-based mode decomposition device that significantly improves measurement precision over traditional spatial light modulators, enabling highly accurate analysis of laser mode content for advanced optical applications.

Contribution

It introduces the first proof-of-principle metasurface device for mode decomposition, achieving over three orders of magnitude better precision than existing methods.

Findings

Achieved mode-weight fluctuation of 6×10⁻⁷ with 1s averaging

Demonstrated reduction in cross-coupling due to small pixel size

Identified noise sources and potential for complete mode decomposition

Abstract

Acquiring precise information about the mode content of a laser is critical for multiplexed optical communications, optical imaging with active wave-front control, and quantum-limited interferometric measurements. Hologram-based mode decomposition devices, such as spatial light modulators, allow a fast, direct measurement of the mode content, but they have limited precision due to cross-coupling between modes. Here we report the first proof-of-principle demonstration of mode decomposition with a metasurface, resulting in significantly enhanced precision. A mode-weight fluctuation of $6\times 10^{-7}$ was be measured with 1 second of averaging at a Fourier frequency of 80 Hz, an improvement of more than three orders of magnitude compared to the state-of-the-art spatial light modulator decomposition. The improvement is attributable to the reduction in cross-coupling enabled by the exceptional small pixel size of the metasurface. We show a systematic study of the limiting sources of noise, and we show that there is a promising path towards complete mode decomposition with similar precision.