# Self-configuring high-speed multi-plane light conversion

## TL;DR

This paper introduces a self-configuring multi-plane light converter that adapts to physical imperfections and enables high-speed optical transformations.

## Contribution

The novel self-configuring MPLC design uses multi-plane wavefront shaping and a high-speed modulator to achieve rapid convergence and high fidelity.

## Key findings

- A self-configuring MPLC was developed that adapts to misalignments and aberrations.
- The system demonstrates arbitrary optical transformations and universal mode sorting.
- The approach enables ultra-high-fidelity optical processing for applications like communications and imaging.

## Abstract

Multi-plane light converters (MPLCs) – also known as diffractive neural networks – convert an orthogonal set of optical fields into any other orthogonal set via a unitary transformation. MPLC design typically involves optimising a digital model. However, inherently high levels of complexity mean that even a minor mismatch between this model and the physically realised MPLC leads to a severe reduction in performance. Here we create a self-configuring MPLC, converging in minutes while automatically absorbing unknown misalignments and aberrations into the design. To achieve this we introduce ‘multi-plane wavefront shaping’ – allowing multiple spatial light modes to be reshaped simultaneously. Convergence is accelerated via a high-speed MPLC platform incorporating a kHz-rate phase-only light modulator. Using this approach we demonstrate arbitrary optical transformations and universal mode sorters. Our work paves the way towards ultra-high-fidelity MPLCs with potential applications to optical communications, photonic computing and imaging.

Multi-plane light converters (MPLCs) rely on complex nonlinear design optimisation and are challenging to physically realise with high fidelity. Here the authors develop a self-configuring free-space MPLC for linear optical information processing.