Thermo-optic phase shifters allow one to dynamically tune and control the operation of integrated-optics interferometers.  The design approach to such devices is often based on finite-element numerical simulations, which provide accurate descriptions of the underlying thermal phenomena, at the price of long computational times. Here, on the contrary, we devise an analytical model for the heat diffusion in a simplified geometrical configuration. The model describes both static and dynamic regimes, and can be conveniently applied both to three-dimensional waveguide devices inscribed by femtosecond laser pulses and to planar lithographic circuits.

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Calibration of sensors is a fundamental step in validating their operation.  Here, we demonstrate the application of a neural-network-based algorithm for the calibration of integrated photonic devices depending on two parameters. We show that a reliable characterization is achievable by carefully selecting an appropriate network training strategy. These results show the viability of this approach as an effective tool for the multiparameter calibration of sensors characterized by complex transduction functions.

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Satellite‐based quantum technologies represent a possible route for extending the achievable range of quantum communication, allowing the construction of worldwide quantum networks without quantum repeaters.  This article reports on qualification of waveguides fabricated in glass by femtosecond laser micromachining for their use in a low Earth orbit space environment. The results we find, combined with the high compatibility of laser‐written optical circuits to quantum communication applications, pave the way for the use of laser‐written integrated photonic components in future satellite missions.

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Single‐photon avalanche diodes (SPADs) are single-photon detectors working at room temperature or slightly below. In this paper, we provide a thorough discussion of the recent progress made in this field, comparing the performance of these devices with the requirements of the quantum photonics applications. Finally, we conclude with our vision for the future.

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On December 14^th, Roberto Osellame participated to the event “CNR in the future”, an online round table organized in order to share ideas and experiences between CNR researchers and some of the members of the Italian Parliament. The Italian Minister of the Research Gaetano Manfredi was present and participated to the discussion.

Achieving ultimate bounds in estimation processes is the main objective of quantum metrology. Finding the optimal strategies to tune the control parameters during the estimation process is a non-trivial problem, and machine learning techniques are a natural solution to address such task. Here, we investigate and implement experimentally an adaptive Bayesian multiparameter estimation technique tailored to reach optimal performances with very limited data. We employ a compact and flexible integrated photonic circuit, fabricated by femtosecond laser writing, which allows to implement different strategies with high degree of control.

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Our work on microstructured integrated photonic circuits fabricated by femtosecond laser micromachining is displayed on the journal cover of Laser & Photonics Reviews .

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Femtosecond laser micromachining allows rapid and cost‐effective fabrication of thermally‐reconfigurable photonic integrated circuits with unique 3D geometries. Here we exploit thermally‐insulating 3D microstructures to decrease the power needed to induce a 2π phase shift down to 37 mW and to reduce the thermal crosstalk to a few percent for an inter‐waveguide separation down to 80 μm.

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Simone Atzeni is giving an invited talk at Young Italian Quantum Information Science Conference (YIQIS) 2020 on Monday 28 September about ‘Structured glass for low power actuation of thermal phase shifters’.

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In this work we demonstrate novel integrated-optics modulators and switches, realized in a glass substrate by femtosecond laser pulses. These devices are based on oscillating microcantilevers, machined by water-assisted laser ablation. Operation frequencies are in the range of tens of kilohertz, thus they markedly overcome the response-time limitation of other glass-based modulators, which rely on the thermo-optic effect.

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