Multimodal Optical Feature Extraction with a Free-Space Photonic Extreme Learning Machine

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Hauptverfasser: Kumari, Anushka, Khisti, Anushree, Choube, Abhinav, Satra, Devansh, Murali, Srivatsa, Kumar, Anshuman
Format: Preprint
Veröffentlicht: 2026
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author Kumari, Anushka
Khisti, Anushree
Choube, Abhinav
Satra, Devansh
Murali, Srivatsa
Kumar, Anshuman
author_facet Kumari, Anushka
Khisti, Anushree
Choube, Abhinav
Satra, Devansh
Murali, Srivatsa
Kumar, Anshuman
contents Photonic extreme learning machines (PELMs) replace a digitally trained hidden layer by a fixed optical transformation, allowing a high dimensional feature map to be generated by physical propagation while only the final readout is learned. Existing free-space PELM demonstrations have established this principle for image and tabular benchmarks, but a unified multimodal optical feature extractor spanning structurally different data types has remained largely undeveloped. Here we demonstrate a single free-space PELM platform for image, audio derived, binary tabular, and regression tasks using phase only SLM encoding, Fourier like free space propagation, and camera intensity detection. The same optical apparatus achieves 96.56% accuracy on MNIST, 95.67% on spoken digit audio from log-Mel spectrograms, 100.00% on Mushroom classification, and 0.0699 NRMSE on Abalone regression. To our knowledge, this is the first free space PELM spanning image, audio derived, and tabular tasks in one physical pipeline, and the first PELM implementation of spectrogram based spoken digit classification. Empirical distance preservation and kernel alignment diagnostics reveal two operating regimes: geometry preserving for image and regression tasks, and distributed class mean accumulation for audio derived spectrograms. These results establish multimodal PELMs as a practical route toward general purpose optical machine learning.
format Preprint
id arxiv_https___arxiv_org_abs_2605_29043
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Multimodal Optical Feature Extraction with a Free-Space Photonic Extreme Learning Machine
Kumari, Anushka
Khisti, Anushree
Choube, Abhinav
Satra, Devansh
Murali, Srivatsa
Kumar, Anshuman
Optics
Photonic extreme learning machines (PELMs) replace a digitally trained hidden layer by a fixed optical transformation, allowing a high dimensional feature map to be generated by physical propagation while only the final readout is learned. Existing free-space PELM demonstrations have established this principle for image and tabular benchmarks, but a unified multimodal optical feature extractor spanning structurally different data types has remained largely undeveloped. Here we demonstrate a single free-space PELM platform for image, audio derived, binary tabular, and regression tasks using phase only SLM encoding, Fourier like free space propagation, and camera intensity detection. The same optical apparatus achieves 96.56% accuracy on MNIST, 95.67% on spoken digit audio from log-Mel spectrograms, 100.00% on Mushroom classification, and 0.0699 NRMSE on Abalone regression. To our knowledge, this is the first free space PELM spanning image, audio derived, and tabular tasks in one physical pipeline, and the first PELM implementation of spectrogram based spoken digit classification. Empirical distance preservation and kernel alignment diagnostics reveal two operating regimes: geometry preserving for image and regression tasks, and distributed class mean accumulation for audio derived spectrograms. These results establish multimodal PELMs as a practical route toward general purpose optical machine learning.
title Multimodal Optical Feature Extraction with a Free-Space Photonic Extreme Learning Machine
topic Optics
url https://arxiv.org/abs/2605.29043