Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array

Abstract To date, most integrated quantum photonics experiments rely on single-photon detectors operating at cryogenic temperatures coupled to photonic integrated circuits (PICs) through single-mode optical fibers. This approach presents significant challenges due to the detection complexity, as cry...

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Main Authors: Giulio Gualandi, Simone Atzeni, Marco Gardina, Antonino Caime, Giacomo Corrielli, Ivan Labanca, Angelo Gulinatti, Ivan Rech, Roberto Osellame, Giulia Acconcia, Francesco Ceccarelli
Format: Article
Language:English
Published: Nature Publishing Group 2025-05-01
Series:Light: Science & Applications
Online Access:https://doi.org/10.1038/s41377-025-01854-6
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author Giulio Gualandi
Simone Atzeni
Marco Gardina
Antonino Caime
Giacomo Corrielli
Ivan Labanca
Angelo Gulinatti
Ivan Rech
Roberto Osellame
Giulia Acconcia
Francesco Ceccarelli
author_facet Giulio Gualandi
Simone Atzeni
Marco Gardina
Antonino Caime
Giacomo Corrielli
Ivan Labanca
Angelo Gulinatti
Ivan Rech
Roberto Osellame
Giulia Acconcia
Francesco Ceccarelli
author_sort Giulio Gualandi
collection DOAJ
description Abstract To date, most integrated quantum photonics experiments rely on single-photon detectors operating at cryogenic temperatures coupled to photonic integrated circuits (PICs) through single-mode optical fibers. This approach presents significant challenges due to the detection complexity, as cryogenic conditions hinder the development of scalable systems. In addition, going towards fully-integrated devices or, at least, removing the optical fibers would be also advantageous to develop compact and cost-efficient solutions featuring a high number of optical modes. This work reports on the direct coupling of a PIC, fabricated by femtosecond laser writing (FLW), and a silicon single-photon avalanche diode (SPAD) array, fabricated in a custom planar technology and compatible with the operation at room temperature. The effectiveness of this solution is shown by achieving perfect coupling and a system detection efficiency as high as 41.0% at a wavelength of 561 nm, which is the highest value reported to date among both heterogeneous/hybrid integrated and directly coupled systems. We also show the robustness of the coupling to misalignments, demonstrating that costly alignment procedures are not needed. Finally, we exploit the SPAD array to characterize a reconfigurable Mach-Zehnder interferometer, i.e., the basic building block of multimode reconfigurable PICs. This solution provides a new avenue to the design and implementation of quantum photonics experiments, especially effective when compact and cost-efficient systems are needed.
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institution Kabale University
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spelling doaj-art-43aeb628339b447284375cbdeabfa6ae2025-08-20T03:54:00ZengNature Publishing GroupLight: Science & Applications2047-75382025-05-0114111110.1038/s41377-025-01854-6Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode arrayGiulio Gualandi0Simone Atzeni1Marco Gardina2Antonino Caime3Giacomo Corrielli4Ivan Labanca5Angelo Gulinatti6Ivan Rech7Roberto Osellame8Giulia Acconcia9Francesco Ceccarelli10Dipartimento di Fisica, Politecnico di MilanoIstituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle RicercheIstituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle RicercheDipartimento di Fisica, Politecnico di MilanoIstituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle RicercheDipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di MilanoDipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di MilanoDipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di MilanoIstituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle RicercheDipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di MilanoIstituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle RicercheAbstract To date, most integrated quantum photonics experiments rely on single-photon detectors operating at cryogenic temperatures coupled to photonic integrated circuits (PICs) through single-mode optical fibers. This approach presents significant challenges due to the detection complexity, as cryogenic conditions hinder the development of scalable systems. In addition, going towards fully-integrated devices or, at least, removing the optical fibers would be also advantageous to develop compact and cost-efficient solutions featuring a high number of optical modes. This work reports on the direct coupling of a PIC, fabricated by femtosecond laser writing (FLW), and a silicon single-photon avalanche diode (SPAD) array, fabricated in a custom planar technology and compatible with the operation at room temperature. The effectiveness of this solution is shown by achieving perfect coupling and a system detection efficiency as high as 41.0% at a wavelength of 561 nm, which is the highest value reported to date among both heterogeneous/hybrid integrated and directly coupled systems. We also show the robustness of the coupling to misalignments, demonstrating that costly alignment procedures are not needed. Finally, we exploit the SPAD array to characterize a reconfigurable Mach-Zehnder interferometer, i.e., the basic building block of multimode reconfigurable PICs. This solution provides a new avenue to the design and implementation of quantum photonics experiments, especially effective when compact and cost-efficient systems are needed.https://doi.org/10.1038/s41377-025-01854-6
spellingShingle Giulio Gualandi
Simone Atzeni
Marco Gardina
Antonino Caime
Giacomo Corrielli
Ivan Labanca
Angelo Gulinatti
Ivan Rech
Roberto Osellame
Giulia Acconcia
Francesco Ceccarelli
Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array
Light: Science & Applications
title Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array
title_full Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array
title_fullStr Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array
title_full_unstemmed Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array
title_short Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array
title_sort laser written reconfigurable photonic integrated circuit directly coupled to a single photon avalanche diode array
url https://doi.org/10.1038/s41377-025-01854-6
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