Abstract
We investigate the absorption properties of U-shaped niobium nitride (NbN) nanowires atop nanophotonic circuits. Nanowires as narrow as 20nm are realized in direct contact with Si3N4 waveguides and their absorption properties are extracted through balanced measurements. We perform a full characterization of the absorption coefficient in dependence of length, width and separation of the fabricated nanowires, as well as for waveguides with different cross-section and etch depth. Our results show excellent agreement with finite-element analysis simulations for all considered parameters. The experimental data thus allows for optimizing absorption properties of emerging single-photon detectors co-integrated with telecom wavelength optical circuits.
Highlights
Nanophotonic circuits allow for realizing complex optical functionality on a chip and enable the assembly of functional devices with many optical components in a scalable fashion
We investigate the absorption properties of U-shaped niobium nitride (NbN) nanowires atop nanophotonic circuits
In this geometry we measure a lower absorption coefficient for the same geometry of the nanowires
Summary
Nanophotonic circuits allow for realizing complex optical functionality on a chip and enable the assembly of functional devices with many optical components in a scalable fashion. By exploiting established fabrication routines originally developed for the electronics industry, high-quality optical networks can be realized. While such circuits have been demonstrated very successfully using silicon as a waveguiding material, recently alternative materials have been investigated that overcome some of the shortcomings of silicon. In particular materials with a wider bandgap are desirable, as they allow for reduced free-carrier absorption and a broader transparency window which covers wavelengths in the visible spectral region. Waveguides based on Si3N4 provide low optical absorption in the infrared [6] and visible [7] wavelength region as well as good mechanical properties [8,9]. Tight confinement of the electrical fields is important for the fabrication of hybrid systems, as for example integrated photonicsuperconducting circuits, where the coupling efficiency of evanescent modes to a nearby
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