Needle-beam generation from SPDC photons using inverse-designed flat optics
Abstract
We experimentally demonstrate the generation of needle-like beams from spontaneous parametric downconversion (SPDC) light using a compact inverse-designed multilevel diffractive lens (MDL). The nonclassical nature of the SPDC source is independently verified through a three-detector heralded Hanbury Brown-Twiss measurement performed before the MDL, yielding a zero-delay second-order correlation value of approximately 0.14. Spatial measurements using an intensified charge-coupled device reveal that the MDL maintains a tightly confined focal distribution over an axial distance of approximately 11 mm under collinear SPDC illumination, substantially reducing diffraction-induced broadening compared with a conventional plano-convex lens of the same nominal focal length. Under non-collinear SPDC illumination, two distinct regions of extended axial confinement are observed, demonstrating the dependence of the engineered focal distribution on the incident spatial field. These results establish a compact flat-optical approach for engineering extended-focus SPDC photon fields, with potential applications in structured quantum photonics.
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BibTeX
@misc{sunny2026needlebeam,
title = {{Needle-beam generation from SPDC photons using inverse-designed flat optics}},
author = {Sunny and Jyotshna Bora and Ayush Tiwari and C. S. Yadav and Rajesh Menon and Amit D. Lad and Vishwa Pal},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.02993},
eprint = {2611.02993},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.02993},
}
RIS
TY - UNPB
TI - Needle-beam generation from SPDC photons using inverse-designed flat optics
AU - Sunny
AU - Jyotshna Bora
AU - Ayush Tiwari
AU - C. S. Yadav
AU - Rajesh Menon
AU - Amit D. Lad
AU - Vishwa Pal
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.02993
UR - https://arxiv.org/abs/2611.02993
AB - We experimentally demonstrate the generation of needle-like beams from spontaneous parametric downconversion (SPDC) light using a compact inverse-designed multilevel diffractive lens (MDL). The nonclassical nature of the SPDC source is independently verified through a three-detector heralded Hanbury Brown-Twiss measurement performed before the MDL, yielding a zero-delay second-order correlation value of approximately 0.14. Spatial measurements using an intensified charge-coupled device reveal that the MDL maintains a tightly confined focal distribution over an axial distance of approximately 11 mm under collinear SPDC illumination, substantially reducing diffraction-induced broadening compared with a conventional plano-convex lens of the same nominal focal length. Under non-collinear SPDC illumination, two distinct regions of extended axial confinement are observed, demonstrating the dependence of the engineered focal distribution on the incident spatial field. These results establish a compact flat-optical approach for engineering extended-focus SPDC photon fields, with potential applications in structured quantum photonics.
ER -