Speaker
Description
Introduction
Wavefront shaping is a powerful tool in modern photonics, enabling precise control over how light propagates through free space and complex media. Conventionally this control comes from a single phase plane displayed on a spatial light modulator (SLM), yet one plane cannot realise the many-to-many mappings that tasks such as mode sorting, optical routing, and arbitrary basis changes require. Multi-plane light converters (MPLCs) overcome this limit by cascading several diffractive phase planes separated by free-space propagation, most often by bouncing a beam repeatedly across different regions of a single SLM. As light diffracts and re-interferes between planes, an MPLC can implement transformations across large sets of spatial modes.
The usual route to building an MPLC is to optimise a digital model of the system and then transfer the resulting phase masks to the experiment. This offline strategy is sensitive to alignment: small misalignments in the early planes cascade through.
Results
Here we demonstrate an MPLC that instead configures itself directly in the experiment[1]. Building on a fast-switching MEMS SLM that updates holograms at kilohertz rates, together with a bespoke optimisation algorithm, our platform tests millions of configurations and converges within minutes rather than the hours demanded by conventional modulators.
The method needs no digital representation of either the optical system or the input fields; it exploits only the mutual orthogonality of the input and target mode sets. We use it to reshape unknown orthogonal speckle fields simultaneously into distinct higher-order Hermite–Gaussian and Laguerre–Gaussian modes with high fidelity. Since the optimisation happens in situ, the converter compensates for misalignment, aberrations, and environmental drift. This removes a barrier to deploying high-dimensional diffractive processors for classical and quantum communications, optical computing, and imaging.
1. A. Rocha, J.C., et al. Self-configuring high-speed multi-plane light conversion. Nat Commun 17, 73 (2026). https://doi.org/10.1038/s41467-025-66798-2
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