Photonic crystal fibres (PCFs)—thin strands of glass with an intricate array of hollow channels running along their length—offer both hollow and solid glass cores, and allow unprecedented control over dispersion and birefringence, ushering in a new era of linear and nonlinear fibre optics, for example: chiral PCF is circularly and topologically birefringent, supporting optical vortices and in some cases strong circular dichroism; through pressure-adjustable dispersion, gas-filled hollow-core PCF provides an elegant means of compressing pulses to single-cycle durations, as well as underpinning a range of unique sources of tunable deep and vacuum ultraviolet light; microparticles optically trapped inside hollow core PCF van be used to sense physical quantities with high spatial resolution; and strong optomechanical effects in solid-core PCF permit stable timing-modulated high harmonic mode-locking at few-GHz repetition rates.

Fabrication of mid-index contrast ring resonators with a well-defined gap is very challenging, while gapless rings suffer from substantial coupling losses. To avoid these issues, we propose a gapless design based on a step-like structuring of the bus/ring waveguides. As we show with numerical simulations, our design allows to spatially confine the modes to the steps formed on the bus/ring waveguides thus mitigating the coupling losses. Additionally, the step on the ring waveguide reduces the bending losses. Finally, we show how varying the heights and widths of the steps allows to tailor the transmittance and quality factor of the ring.

Free-standing thin-film waveguides and slot waveguides offer excellent properties for gas sensing: high air confinement factors resulting in strong light-analyte interaction, reduced material absorption loss, and negligible Fabry-Perot fringes. We demonstrate that such waveguides combined with the sensitive and selective technique of mid-IR laser absorption spectroscopy can detect methane and carbon dioxide down to 300 ppb and 30 ppb levels, respectively. Isotope specific detection of CO2 with excellent 13C isotope ratio accuracy of 0.3‰ has also been shown. The unprecedented sensitivity together with miniature sensor footprint and microlitre sample volumes open new application areas in biology, environmental sensing and industral process monitoring.

The realistic implementation of quantum architectures relies on the development of scalable, resource-efficient platforms that are compatible with today's fiber networks. Here we will demonstrate novel schemes utilized for time-/frequency-bin entanglement generation and processing, achieved by leveraging current photonics infrastructures.

The relation between polarization singularities and optical properties in metasurfaces is a hot topic in nanophotonics. In this work, we focus on dielectric metasurfaces supporting nondegenerate photonic bands, leading to symmetry-protected Bound States in a Continuum (BICs) that become Circularly Polarized States (CPS) upon symmetry reduction. First, we discuss how BICs and CPS lead to polarization singularities in the far field, whose winding numbers – or topological charges – follows from the symmetry of the lattice. Then, we determine the polarization properties via the Stokes parameters, focusing on the conditions for the occurrence of a nonvanishing circular polarization. Finally, we calculate the optical response in reflection and the degree of circular dichroism. The results shed light on the role of polarization singularities and symmetry in determining the optical chirality.

Atomically thin two-dimensional transition metal dichalcogenides have fascinated researchers due to their unique electronic and optical properties. The control of exciton-trion dynamics in two-dimensional semiconductors is critical for their application in optoelectronic devices. One way to engineer the exciton-trion dynamics is by applying strain in the monolayers of these two-dimensional materials using nanostructured substrates. Here we demonstrate a versatile route to engineering the exciton-trion dynamics in monolayer WSe2 by applying biaxial strain. A polytetrafluoroethylene (PTFE) nanocone array decorated by thin gold film and fabricated via colloidal lithography is used to create the strain in the superposed monolayer. To distinguish the effect of strain and plasmonics, we compare our results on the nanocone surface with the one for monolayer WSe2 on a plane gold film.

Periodically patterning silicon with a subwavelength period enables flexible control of the propagation of light and sound in silicon photonic circuits. In this invited presentation, we will show our most recent demonstration of supercontinuum generation in the near-IR and mid-IR using suspended silicon waveguides. We will also discuss our recent results on subwavelength engineering of photons and phonons in suspended and non-suspended silicon optomechanical cavities

In this talk we present our recent advances in SWG metamaterial engineering. We will show a 1D-optical phased array composed of 112 evanescent-coupled surface emitting antennas with a length of 1.5 mm and fed by a compact distributed Bragg deflector. The measurements demonstrate a wavelength-steerable collimated beam with a far-field angular divergence of 1.8o × 0.2o. Experimental results of a bricked SWG 2×2 MMI coupler are also shown, achieving polarization agnostic performance in the 1500nm to 1560nm wavelength range. Both devices were fabricated on a standard 220-nm SOI platform using a single full-etch step process, with a minimum feature size of 80 nm, and thus compatible with immersion deep-UV lithography.

A review of different integration platforms for high-Q Whispering Gallery Mode bulk resonators is presented, including SOI slotted photonics crystal waveguides, suspended Si photonic crystal membranes or suspended silica waveguides. While each of these approaches allows coupling to a specific monolithic resonator, including those made in low index materials, a novel architecture, based on metamaterial engineered silicon photonics waveguides, provides unique flexibility to couple a wide range of WGM microresonators, enabling the combination of high-performance resonators with complex Si photonic circuits.

Recent advancements in nanofabrication technology have allowed for the implementation of nanostructures smaller than the wavelength of light on photonic chips. Integrating mature photonic waveguide technologies with concepts derived from nanophotonics offers exciting possibilities for achieving unparalleled manipulation of guided light waves. Nevertheless, the task of creating novel functionalities while maintaining efficiency and compatibility with existing technology poses a major challenge in the field of on-chip nanophotonics. Here, we introduce a new type of silicon-based optical meta-waveguide operating in the telecom spectral range. Our waveguides comprise a chain of Mie-resonant silicon nano resonators designed to exhibit nearly exclusively forward-scattering characteristics. This yields unique optical properties, including a large transmission gain and efficiently suppressed backscattering even in the presence of strong perturbations. This is an unprecedented combination of characteristics for any photonic system supporting guided modes, thereby unlocking completely new opportunities for fundamental research as well as future applications.

A programmable photonic integrated processor is used to perform processing on free-space optical beams. Specifically, a free-space transmitter and receiver capable of handling multiple channels is implemented, realizing an adaptive MIMO system. The processors allow the mitigation of atmospheric turbulence in a Free Space Optical communication link. A system with two photonic processors is demonstrated to automatically find and shape the beams required for establishing orthogonal channels, also in presence of path perturbations and obstacles. The processors are realized in silicon photonics and are implemented by a self-configuring binary mesh of integrated Mach-Zehnder Interferometers (MZIs). Integrated Optical Phased Array antennas with 16 elements generate and receive suitable optical beams. 10 Gbit/s OOK signals are successfully transmitted on an indoor setup emulating hundreds of meters link.

The presence of a vertical component to the transition dipole moment in interlayer excitons, which suppresses electron-hole overlap, results in longer radiative lifetimes as compared to intralayer excitons. Such tightly bound interlayer excitons well-suited candidates for valley-based quantum information processing applications. Their optical accessibility is, however, limited due to their out-of-plane transition dipole moment. We first design a system to strengthen the coupling of interlayer excitons in two-dimensional (2D) material heterostructures with Purcell enhanced out-of-plane resonant modes of a Whispering Gallery Mode (WGM) resonator at room temperature. The high quantum confinement of light in a small modal volume and high Q-factor allow a much stronger coupling of these excitons to the electromagnetic field. We then discuss how to engineer an asymmetric transmission of light from these excitons, which facilitates readout from such systems. We also present our attempts to experimentally demonstrate the valley selective separation and routing of interlayer excitons in the MoSe2/WSe2 heterobilayer stack of TMDCs material by integrating on a planar silicon nitride (SiN) bus-waveguide coupled with a microring resonator (MRR).

Waveguides bending are basic and important structures for high integration optics and circuits allowing to change the wave propagation direction [1]. Due to the abrupt change of the propagation direction of light over the discontinuity region reflection and radiation is expected to occurs and complex numerical techniques, such as the finite element method, should be used for the modeling of such structure while at the same time it requires knowledge of advanced electromagnetic theory and high computational effort and resources. On the other hand, complex neural networks architectures and machine learning algorithms have been used for the modeling of optical fiber couplers [2] and optical fibers and tapers [3]. The main advantages of machine learning based models are their simplicity, the reduced computational effort and time and also their application for synthesis problems. In this work, a machine learning algorithm has been implemented for the modeling of waveguides bending based on Silicon on Silica with a resonator at the bending. The refractive indexes are n1 = 3.476 and n2 =1.444. and the cavity size is defined by the coordinates of five coordinate points. The data set for the training and validation of the proposed model has been obtained by an efficient frequency domain finite element method [4]. Regression higher than 0.98 has been obtained for the efficiency computation. The obtained model is simple, it is less time-consuming and it requires less computational-effort than conventional numerical techniques used for the analysis of this kind of problems. As a conclusion waveguides bending can be analyzed by using machine learning algorithms. Additionally, a machine learning model can be easily adapted for the analysis of several other photonic and plasmonic devices.