Enhanced orbital-angular-momentum dimensionality and spatial-spectral decoupling in thin-film SPDC
Abstract
Thin-film spontaneous parametric down-conversion, due to the relaxed phase-matching condition, generates photon pairs that are extremely broadband in frequency and angle and highly entangled in time/frequency and position/momentum. Here we show that it also provides a very broad orbital angular momentum (OAM) spectrum, which, in contrast to the case of bulk crystals, is decoupled from the frequency spectrum. To demonstrate it experimentally, we generate photon pairs in a 7 μm-thick lithium niobate film and compare them with those from a 500 μm-thick periodically poled lithium niobate crystal under identical pump conditions. The thin-film source exhibits a substantially broader OAM spectrum, with the azimuthal Schmidt number almost 9 times larger than that of the bulk source. On this highly entangled state, we perform quantum-state tomography in selected two- and four-dimensional OAM subspaces, demonstrating high-purity maximally entangled states. These results highlight thin nonlinear films as a promising platform for high-dimensional quantum-state generation with weak spatial--spectral coupling.
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BibTeX
@misc{akatev2026enhanced,
title = {{Enhanced orbital-angular-momentum dimensionality and spatial-spectral decoupling in thin-film SPDC}},
author = {Dmitrii Akatev and Jakub Lewandowski and Maria Chekhova},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28020},
eprint = {2610.28020},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28020},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Enhanced orbital-angular-momentum dimensionality and spatial-spectral decoupling in thin-film SPDC
AU - Dmitrii Akatev
AU - Jakub Lewandowski
AU - Maria Chekhova
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28020
UR - https://arxiv.org/abs/2610.28020
AB - Thin-film spontaneous parametric down-conversion, due to the relaxed phase-matching condition, generates photon pairs that are extremely broadband in frequency and angle and highly entangled in time/frequency and position/momentum. Here we show that it also provides a very broad orbital angular momentum (OAM) spectrum, which, in contrast to the case of bulk crystals, is decoupled from the frequency spectrum. To demonstrate it experimentally, we generate photon pairs in a 7 μm-thick lithium niobate film and compare them with those from a 500 μm-thick periodically poled lithium niobate crystal under identical pump conditions. The thin-film source exhibits a substantially broader OAM spectrum, with the azimuthal Schmidt number almost 9 times larger than that of the bulk source. On this highly entangled state, we perform quantum-state tomography in selected two- and four-dimensional OAM subspaces, demonstrating high-purity maximally entangled states. These results highlight thin nonlinear films as a promising platform for high-dimensional quantum-state generation with weak spatial--spectral coupling.
ER -