An overview of the most recent developments and improvements to the low-loss TriPleX Si 3 N 4 waveguide technology is presented in this paper. The TriPleX platform provides a suite of waveguide geometries (box, double stripe, symmetric single stripe, and asymmetric double stripe) that can be combined to design complex functional circuits, but more important are manufactured in a single monolithic process flow to create a compact photonic integrated circuit. All functionalities of the integrated circuit are constructed using standard basic building blocks, namely straight and bent waveguides, splitters/combiners and couplers, spot size converters, and phase tuning elements. The basic functionalities that have been realized are: ring resonators and Mach-Zehnder interferometer filters, tunable delay elements, and waveguide switches. Combination of these basic functionalities evolves into more complex functions such as higher order filters, beamforming networks,

The development of large-scale optical quantum information processing circuits ground on the stability and reconfigurability enabled by integrated photonics. We demonstrate a reconfigurable 8×8 integrated linear optical network based on silicon nitride waveguides for quantum information processing. Our processor implements a novel optical architecture enabling any arbitrary linear transformation and constitutes the largest programmable circuit reported so far on this platform. We validate a variety of photonic quantum information processing primitives, in the form of Hong-Ou-Mandel interference, bosonic coalescence/anticoalescence and high-dimensional single-photon quantum gates. We achieve fidelities that clearly demonstrate the promising future for large-scale photonic quantum information processing using low-loss silicon nitride.

Hybrid integrated semiconductor laser sources offering extremely narrow spectral linewidth as well as compatibility for embedding into integrated photonic circuits are of high importance for a wide range of applications. We present an overview on our recently developed hybrid-integrated diode lasers with feedback from low-loss silicon nitride (Si3N4 in SiO2) circuits, to provide sub-100-Hz-level intrinsic linewidths, up to 120 nm spectral coverage around 1.55 µm wavelength, and an output power above 100 mW. We show dual-wavelength operation, dual-gain operation, laser frequency comb generation, and present work towards realizing a visible-light hybrid integrated diode laser.

We demonstrate a reconfigurable 8×8 photonic integrated circuit suitable for implementing universal gates for quantum information processing protocols. The processor is implemented as a square mesh of tunable beam splitters based on stoichiometric silicon nitride waveguides, containing 128 tunable elements. In order to demonstrate its versatility, we perform a variety of photonic quantum information processing primitives, in the form of Hong-Ou-Mandel interference, bosonic coalescence/anti-coalescence and highdimensional single-photon quantum gates exploiting the whole mode structure of the processor. We achieve fidelities that demonstrate the potential for large-scale photonic quantum information processing using stoichiometric silicon nitride.

Photonics-based techniques spearhead the generation of high-frequency signals in the millimeter-andTerahertz wave, crucial for ultrabroadband mobile wireless link development. Photonic integration is enabling to provide the photonic approach with added advantages of energy-efficiency, flexibility and scalability, in addition to signal quality. We present an optical heterodyne system based on a novel dual laser module containing two InP-Si 3 N 4 hybrid lasers with intracavity wavelength selective optical filters with output optical power per laser of up to 15 dBm (31 mW), wide wavelength tuning of about 60 nm, and narrow optical linewidth below 100 kHz. To the best of our knowledge, we present for the first time the continuous-wave generation of RF frequencies over a wide tuning range from C-band (4 GHz -8-GHz) to W-band (75 GHz -110 GHz) achieving record low RF electrical linewidth around 108 kHz and long-term drift < 12 MHz with two free-running lasers. This is the best beat-note linewidth obtained with such an integrated source in a free-runnning regime and with a wide tuning range ever reported.Index Terms-photonic integration, millimeter-waves, hybrid laser, laser tuning. I. INTRODUCTIONT is expected that networks will utilize frequency bands in the millimeter-wave range (30 to 300 GHz) to deliver extreme link capacities and miniaturize transceivers [1]. These are key parameters to unlock the radio access densification in urban scenarios through wireless backhaul of small cells,