Silicon Photonics shows considerable potential as a radiation-hard technology for building the optical data transmission links for future high-energy physics experiments at CERN. Optical modulators are a key component of optical links, which will need to withstand radiation doses in excess of 10 MGy. The geometrical parameters and doping concentrations of two popular types of Silicon Photonics modulators, Mach-Zehnder and Ring Modulators, have been varied in order to study their impact on the device radiation tolerance. They were exposed to an X-ray beam to test their resistance to ionizing radiation. The Ring Modulator with the highest doping concentration is shown to be the most tolerant, showing no degradation in performance up to the highest dose of 11 MGy. Moreover, we report first evidence of the dependence of the radiation tolerance on the Ring Modulator operating temperature.

Waveguide-Integrated Germanium-on-Silicon (Ge-on-Si) photodiodes are integral components in silicon photonics and understanding their radiation tolerance is important for applications that intend to use silicon photonics in harsh radiation environments. Here we report the results of high fluence particle irradiation tests on Ge-on-Si photodiodes. The photodiode samples are irradiated using neutrons and protons, with fluences reaching up to 3 × 10 ¹⁶ n/cm ² (23 MeV) and 4.1 × 10 ¹⁶ p/cm ² (24 GeV), respectively. Throughout the neutron irradiation, changes in photodiode responsivity and dark current are monitored, while the capacitance and current-voltage characteristics are measured during the proton irradiation test. The results reveal only minimal losses in responsivity, along with moderate increases in dark current and capacitance. These observed changes could impose limitations on applications that demand high bandwidth in extreme radiation environment. However, it is worth noting that for example high-energy physics experiments, which represent some of the most extreme radiation environments, do not necessarily require exceptionally high receiver bandwidths. Consequently, our findings demonstrate excellent radiation tolerance that fulfills the requirements of next-generation high-energy physics experiments.

Silicon Photonics enables the manufacturing of high-speed, low power integrated optical circuits with compact foot-prints, and recent studies have also shown it to have high tolerance to radiation. The technology has, therefore, been identified as an excellent candidate for the development of the next generation of radiation-tolerant optical links for High Energy Physics Experiments at CERN. This paper presents the results of characterization and modelling of building block devices and circuits for custom radiation-tolerant transceivers based on Silicon Photonics. We demonstrate a 4-channel Wavelength Division Multiplexing transmitter based on micro-ring modulators operating at 25 Gb/s per lane, and a polarization insensitive receiver based on Germanium photodiodes. Solutions for the thermal tuning of the ring modulators and for on-chip active polarization control are also reported.

We propose two configurations for the coexistence of sensing and communication signals, exploiting Free Space Optical (FSO) links to transmit commercial 6G traffic and remotely interrogate sensors distributed along distances of 100 m. The sensors are fabricated on a Silicon Photonics (SiPh) platform, to achieve miniaturization and highly compact form of the required features. The first scheme consists of couplers and circulators, while the second utilizes polarization handling elements to multiplex both signals, while a 100-m outdoor Free Space Optical link is utilized for both schemes. The configurations exhibit high stability, with uninterrupted transmission of traffic along the duration of the experiments, while the sensors’ performance is evaluated, with their discrepancies measured below 2%.

Light detection and ranging (Lidar) is a key enabling technology for autonomous vehicles and drones. Its emerging implementations are based on photonic integrated circuits (PICs) and optical phased arrays (OPAs). In this work, we introduce a novel approach to the design of OPA Lidar antennas based on Si₃N₄ grating couplers. The well-established TriPleX platform and the asymmetric double stripe waveguide geometry with full etching are employed, ensuring low complexity and simple fabrication combined with the low-loss advantages of the platform. The design study aims to optimize the performance of the grating coupler-based radiators as well as the OPA, thus enhancing the overall capabilities of Si₃N₄-based Lidar. Uniform and non-uniform grating structures are considered, achieving θ and φ angle divergences of 0.9° and 32° and 0.54° and 25.41°, respectively. Also, wavelength sensitivity of 7°/100 nm is achieved. Lastly, the fundamental OPA parameters are investigated, and 35 dBi of peak directivity is achieved for an eight-element OPA.

Carbon fiber-reinforced composites have become a staple in the aerospace industry, owing to their mechanical properties (low weight and mechanical stability). Resin transfer molding (RTM) is a manufacturing process for composite materials, offering significant cost reduction, compared to autoclave processes. To achieve the desired quality though, strict control of several process conditions is required. Monitoring the temperature and pressure conditions inside the tool along with the resin’s refractive index (RI) (monitoring its cure state), can provide tight control over the curing cycle. Leveraging silicon photonics advantages (electrically passive and stable at high temperatures) can enable accurate tracking of the resin curing conditions. In this work, the first demonstration of silicon photonic sensors in the production of composite parts is presented. The sensors’ high thermo-optic sensitivity (78.4 pm/°C) and linearity (0.9787) are leveraged, while being deployed inside a multiton composite tool. The devices are demonstrated under demanding temperature (up to $165~^{\circ }$ C) and pressure (7 bar) conditions, during a 6-h production cycle, compatible with an RTM-6 (aerospace-grade RTM) process. It shows highly stable performance across the full dynamic range ( $30~^{\circ }$ C– $165~^{\circ }$ C), accurately monitoring the cure state of the resin.