Compact, on‐chip spectrometers exploiting tailored disorder for broadband light scattering enable high‐resolution signal analysis while maintaining a small device footprint. Due to multiple scattering events of light in the disordered medium, the effective path length of the device is significantly enhanced. Here, on‐chip spectrometers are realized for visible and near‐infrared wavelengths by combining an efficient broadband fiber‐to‐chip coupling approach with a scattering area in a broadband transparent silicon nitride waveguiding structure. Air holes etched into a structured silicon nitride slab terminated with multiple waveguides enable multipath light scattering in a diffusive regime. Spectral‐to‐spatial mapping is performed by determining the transmission matrix at the waveguide outputs, which is then used to reconstruct the probe signals. Direct comparison with theoretical analyses shows that such devices can be used for high‐resolution spectroscopy from the visible up to the telecom wavelength regime.

Integrated quantum photonics enables the generation, manipulation, and detection of quantum states of light in miniaturized waveguide circuits. Implementation of these three operations in a single integrated platform is a crucial step toward a fully scalable approach to quantum photonic technologies. In this context, diamond has emerged as a particularly promising material as it naturally combines a large transparency range for the fabrication of low‐loss photonic circuits, and a variety of optically active defects for the realization of efficient single‐photon emitters. Furthermore, its high Young's modulus makes it ideal for the implementation of tunable optomechanical devices for active quantum state manipulation. This review reports recent progress on the realization of the main components required for a diamond‐based integrated quantum photonic architecture: single‐photon emitters, static and actively tunable waveguide circuits, and, as a last building block, integrated superconducting single‐photon detectors.

No abstract

Harnessing tailored disorder for broadband light scattering enables high-resolution signal analysis in nanophotonic spectrometers with a small device footprint. Multiple scattering events in the disordered medium enhance the effective path length which leads to increased resolution. Here we demonstrate an on-chip random spectrometer cointegrated with superconducting single-photon detectors suitable for photon-scarce environments. We combine an efficient broadband fiber-to-chip coupling approach with a random scattering area and broadband transparent silicon nitride waveguides to operate the spectrometer in a diffusive regime. Superconducting nanowire single-photon detectors at each output waveguide are used to perform spectral-to-spatial mapping via the transmission matrix at the system, allowing us to reconstruct a given probe signal. We show operation over a wide spectral range with sensitivity down to powers of −111.5 dBm in the telecom band.

A new approach for an optical actuator system based on mixed ionic–electronic conductor materials is proposed. The system actuates on light propagating in a waveguide implemented on a photonic integrated circuit by electrochemically changing the composition of the MIEC material, using the characteristic dependence of the optical properties upon stoichiometry. To realize this actuator, a multilayer stack was sputtered and characterized forming a battery-like system where ions reversibly travel from a Li-ion source to a Li x V2O5 layer, producing the desired change of the optical properties. Modal field FEM simulations were carried out to estimate the influence of the formed actuator on a waveguide fundamental mode implemented on the silicon on insulator platform. The time resolution of the actuator is estimated solving the diffusion profile of Li inside the Li x V2O5 coating and its evolution with time. Through simulations and measurements, promising results for a potential actuator system are shown, like small device length (<20 μm), low power consumption (∼10 pW per switch), reversibility, and long time stability.

The field of quantum information processing offers secure communication protected by the laws of quantum mechanics and is on the verge of finding wider application for the information transfer of sensitive data. To improve cost-efficiency, extensive research is being carried out on the various components required for high data throughput using quantum key distribution (QKD). Aiming for an application-oriented solution, we report the realization of a multichannel QKD system for plug-and-play high-bandwidth secure communication at telecom wavelengths. We designed a rack-sized multichannel superconducting nanowire single photon detector (SNSPD) system, as well as a highly parallelized time-correlated single photon counting (TCSPC) unit. Our system is linked to an FPGA-controlled QKD evaluation setup for continuous operation, allowing us to achieve high secret key rates using a coherent-one-way protocol.

Diamond has emerged as an optimal platform for the realization of fully integrated quantum photonic technologies. In the cover image, a set of electrically tunable color centers supply a source of indistinguishable single photons in different diamond waveguides; a network of directional couplers and opto‐mechanical phase shifters is employed for active manipulation of quantum states of light, which are detected at the output of the circuit by integrated superconducting single photon detectors. For further details see the Review (article number https://doi.org/10.1002/qute.201800061) by Wolfram Pernice and co‐workers.

No abstract