We report experimental results of label-free anti-bovine serum albumin (anti-BSA) antibody detection using a SOI planar photonic crystal waveguide previously bio-functionalized with complementary BSA antigen probes. Sharp fringes appearing in the slow-light regime near the edge of the guided band are used to perform the sensing. We have modeled the presence of these band edge fringes and demonstrated the possibility of using them for sensing purposes by performing refractive index variations detection, achieving a sensitivity of 174.8 nm/RIU. Then, label-free anti-BSA biosensing experiments have been carried out, estimating a surface mass density detection limit below 2.1 pg/mm² and a total mass detection limit below 0.2 fg.

We report an experimental demonstration of single-strand DNA (ssDNA) detection at room temperature using a photonic-crystal-waveguide-based optical sensor. The sensor surface was previously biofunctionalized with ssDNA probes to be used as specific target receptors. Our experiments showed that it is possible to detect these hybridization events using planar photonic-crystal structures, reaching an estimated detection limit as low as $19.8\mathrm{nM}$ for the detection of the complementary DNA strand.

A two-layer switch exploiting orbital angular momentum (OAM) and wavelength of the light as switching domains is presented, aiming to increase the scalability with respect to the single-layer switches. The switch is able to accept 160 optical Gaussian data inputs on a 16-channel wavelength division multiplexing (WDM) grid and direct each input signals to different output ports exploiting 10 OAMs. The optical switch is based on an integrated OAM multiplexer followed by a compact OAM demultiplexer consisting of two refractive elements. Its experimental characterization confirmed a total enabled throughput of 19.2 Tb/s, thanks to the 30 GHz bandwidth available for each port. The switching time can be lower than 1 s. The OAM switch power consumption, solely due to the thermal tuning of the OAM emitters, since the OAM demux is passive, is 1.35 mW/Gb/s. In the proposed switching architecture the number of active components, i.e. the power consumption, scales linear with the number of ports. This is favorable in comparison with single-layer switches that cascade e.g. 2x2 elementary blocks to obtain large port counts, which scale with the square of the number of ports. The switch accepts input and output signals with Gaussian phase profile that propagate through optical fibers and waveguides, thus making it compatible with standard telecom devices. The suitability of the switch to support real data-traffic is proved by successfully testing it with 10G Ethernet and Fiber Channel over Ethernet (FCoE) data traffic and video traffic. A possible application scenario is represented by a data-center network where the switch can be used to create a low-power consumption network parallel to the network based on standard electronic routers, to manage large traffic flows.

The evolution of microwave and mm-wave systems for communication and remote sensing is heading towards a massive deployment of phased-array antennas with beamforming capabilities. 5G wireless access networks are expected to employ beamforming to optimize resources allocation, whereas radars will benefit from precise and fast-switching antennas. Moreover, in the next future, those systems are expected to widely employ photonic technologies for signal generation, acquisition, and distribution. In this scenario, photonics can allow for the development of high-performance beamforming networks, which can easily be integrated in photonics-assisted RF systems, combining broad operational bandwidth, low signal distortion, and high pointing precision with unprecedented flexibility. In this paper, a phase shift-based beamforming network for microwave applications is presented and its performance analyzed. The Si-photonics integrated phase shifters exhibit large phase shift (> 360°) and limited amplitude fluctuations (~ 2.5 dB). The packaged beamforming network elements show extremely low signal distortion, low steering error (<3°), and fast switching time (< 5 ns), demonstrated by the transmission with beam-steering of a 2-Gb/s communication signal and of a 1-GHz chirped radar waveform. A comparison with commercial RF devices shows that the photonics-assisted beamforming network is well-suited for high bit-rate 5G communications and for wideband radar applications.

A four-orbital angular momentum (OAM) modes converter consisting of the cascade of an OAM demultiplexer and an OAM multiplexer is implemented and characterized. The OAM multiplexer is realized with an integrated photonic circuit based on four tunable OAM emitters, i.e. the order of the emitted OAM mode can be selected by thermal tuning. It works on linearly polarized signals. The OAM demultiplexer, completely passive, consists of the cascade of two patterned refractive elements followed by a lens and can work independently of the polarization of the input signals. The proposed OAM converter can receive at its input a bundle of spatially multiplexed beams mapped on different OAM modes, each one carrying a set of wavelength division multiplexed (WDM) channels. Each WDM channel can be independently converted to a different OAM mode and all the OAM beams are multiplexed at the converter output. The performance of the proposed scheme is assessed as a function of the order of the OAM beam before and after the conversion, as well as of the wavelength of the input signal. The measurements show a power penalty on the bit error-rate (BER) curves of less than 1 dB in all the considered cases. The scheme is tested also with 100 Gb/s real data-traffic generated with commercial network cards, showing full operability. The cascading ability of the proposed scheme is also investigated in an experiment where the signal to be converted is generated by an OAM multiplexer, i.e. the output stage of the OAM converter, showing a penalty of less than 2 dB. Moreover, considerations on scalability, bandwidth and power consumption are also included along with a possible application of OAM conversion within add/drop nodes in an OAM-wavelength multiplexed transmission scenario.