Self-configuring high-speed multi-plane light conversion (2501.14129v1)

Abstract: Multi-plane light converters (MPLCs) - also known as linear diffractive neural networks - are an emerging optical technology, capable of converting an orthogonal set of optical fields into any other orthogonal set via a unitary transformation. MPLC design is a non-linear problem typically solved by optimising a digital model of the optical system. However, inherently high levels of design complexity mean that even a minor mismatch between this digital model and the physically realised MPLC leads to a severe reduction in real-world performance. Here we address this challenge by creating a self-configuring free-space MPLC. Despite the large number of parameters to be optimised (typically tens of thousands or more), our proof-of-principle device converges in minutes using a method in which light only needs to be transmitted in one direction through the MPLC. Two innovations make this possible. Firstly, we devise an in-situ optimisation algorithm combining wavefront shaping with the principles of wavefront matching that would conventionally be used to inverse-design MPLCs offline in simulation. Secondly, we introduce a new MPLC platform incorporating a microelectromechanical system (MEMS) phase-only light modulator - allowing rapid MPLC switching at up to kiloHertz rates. Our scheme automatically accounts for the physical characteristics of all system components and absorbs any unknown misalignments and aberrations into the final design. We demonstrate self-configured MPLCs capable of mapping random orthogonal speckle input fields to well-defined Laguerre-Gaussian and Hermite-Gaussian output modes, as well as universal mode sorters. Our work paves the way towards large-scale ultra-high-fidelity fast-switching MPLCs and diffractive neural networks, which promises to unlock new applications in areas ranging from optical communications to optical computing and imaging.

• The paper presents a free-space MPLC that self-configures through in-situ optimization to achieve high-fidelity optical mode conversion despite physical aberrations.
• It introduces a MEMS-based phase-only modulator enabling kilohertz switching, drastically reducing configuration times by optimizing tens of thousands of parameters in minutes.
• Experimental results confirm successful transformation of random speckle inputs into precise Hermite-Gaussian and Laguerre-Gaussian modes, enhancing capabilities in optical communications and imaging.

Self-Configuring High-Speed Multi-Plane Light Conversion

The paper "Self-configuring high-speed multi-plane light conversion" addresses the challenge of designing efficient multi-plane light converters (MPLCs), a burgeoning technology in the domain of optical mode transformation. MPLCs offer the capacity to convert one orthogonal set of optical fields into another via unitary transformations. The intrinsic complexity of MPLC design often results in a pronounced decline in real-world performance due to mismatches between digital models and physical implementations. This research endeavors to resolve this issue by developing a self-configuring free-space MPLC, capable of accurate mode conversion and alignment within the actual optical system, sidestepping the constraints of conventional pre-defined digital models.

The research presents several key innovations. Firstly, the authors develop an in-situ optimization algorithm for MPLCs based on wavefront shaping and wavefront matching principles. This algorithm is designed to optimize the MPLC configuration directly within the optical system, accommodating physical inaccuracies and optical aberrations that arise in practice. Secondly, they introduce a novel MPLC architecture, utilizing a microelectromechanical system (MEMS)-based phase-only light modulator. This MEMS device enables rapid switching at kilohertz rates, which significantly reduces the optimization time for configuring MPLCs.

A notable aspect of the self-configuring MPLC described here is its ability to optimize tens of thousands of parameters in a matter of minutes, a substantial reduction in timescale compared to traditional methods. The system automates the process of aligning optical components and mitigating aberrations, thereby achieving high-fidelity transformation of optical modes with minimal manual intervention.

Experimental results demonstrate the efficacy of the system, showing successful conversion of random orthogonal speckle inputs to well-defined Hermite-Gaussian and Laguerre-Gaussian modes with high fidelity. The system also functions as a universal mode sorter, indicating its versatility across multiple applications including optical communications, computing, and imaging.

The implications of this research are significant, given the growing demand for high-dimensional light manipulation in advanced photonics applications. The ability to achieve ultra-high-fidelity mode conversion and rapid reconfiguration of MPLCs can drive new advancements in optical communications, such as high-capacity data transmission over multimode fibers, and in imaging systems that require precise light control for enhanced resolution.

Looking forward, the integration of self-configuring MPLCs with other photonic technologies, like photonic integrated circuits, could catalyze the development of more compact and efficient optical systems. Furthermore, as MEMS technology continues to advance, the enhancement in modulation speed and efficiency could lead to MPLCs capable of handling even more complex transformations at higher speeds. The convergence of these technologies holds promise for expanding applications in optical computing and beyond, where the manipulation of light modes is crucial.