Research Activity optoelectronics
Optoelectronics
Surface-enhanced Raman spectroscopy (SERS) and plasmonic sensors represent advanced analytical techniques that leverage the interaction between light and nanostructured metallic surfaces to enhance the detection of molecular signals. SERS utilizes plasmonics to significantly amplify the Raman scattering signals of molecules, making it a powerful tool for obtaining a large amount of information at molecular level. Plasmonic sensors, on the other hand, exploit the localized surface plasmon resonance (LSPR) phenomenon to detect changes in the refractive index near the sensor surface, offering high sensitivity and specificity. Both technologies have found applications across various fields, including medical diagnostics, biology, chemistry, analysis of impurities, environmental monitoring, and anti-counterfeiting.
The plasmonic and SERS sensor project involves a series of integrated activities covering design, manufacturing, testing and performance analysis to optimize the effectiveness of devices in both planar and fiber configurations. For plasmonic sensors, design starts with theoretical modelling of structures, studying optical properties to determine the best geometry and composition of materials that can maximize the plasmonic response according to specific applications (i.e. detection of biomolecules).
From these considerations, the project moves on to the construction phase. During this phase, advanced deposition and lithography techniques are used to develop sensors with optimized plasmonic properties. The performance of the manufactured sensors is then analysed by means of experimental tests, in which both the thermal stability and the sensitivity of the device are assessed under simulated or real operating conditions to ensure their reliability and effectiveness. Thermal analysis plays a key role, as the stability of the plasmonic resonance can be affected by temperature variations, so measurements are conducted to identify any critical thermal effects [1]. For sensors based on enhanced surface Raman spectroscopy (SERS), the approach starts from the theoretical design of the device via numerical simulators such as COMSOL, to optimize geometry and material engineering to ensure an enhanced Raman signal. In this phase, the electromagnetic field behavior is studied in detail, trying to obtain hot spots (hot spots) that significantly increase the sensitivity of the sensor [2].
The choice of geometry and materials becomes essential to optimize the Raman amplification factor, both for planar devices and integrated fiber-optic structures. The experimental phase then involves testing the structures by Raman spectroscopy to assess the effectiveness of the SERS surface in terms of signal sensitivity and resolution. These tests allow us to compare the performance obtained with theoretical models, further refining the design parameters to optimize the effectiveness of the sensor [3,4]. This integration of theoretical modelling, manufacturing, experimental testing and thermal analysis allows the development of high performance plasmonic and SERS sensors for use in a wide range of advanced chemical and biological detection applications.
[1] Principe, S., Giaquinto, M., Micco, A., Cutolo, M. A., Riccio, M., Breglio, G., … & Cusano, A. (2020). Thermo-plasmonic lab-on-fiber optrodes. Optics & Laser Technology, 132, 106502.
[2] Cutolo, A., Carotenuto, A. R., Cutolo, M. A., Cutolo, A., Giaquinto, M., Palumbo, S., … & Fraldi, M. (2022). Ultrasound waves in tumors via needle irradiation for precise medicine. Scientific Reports, 12(1), 6513.
[3] Cutolo, M. A., Galeotti, F., Spaziani, S., Quero, G., Calcagno, V., Micco, A., … & Cusano, A. (2024). Self‐Assembled Hierarchical Nanostructures: Toward Engineered SERS‐Active Platforms. Laser & Photonics Reviews, 2301056.
[4] Cutolo, M. A., Galeotti, F., Spaziani, S., Quero, G., Calcagno, V., Micco, A., … & Pisco, M. (2024, June). Engineering SERS-active substrates: design and characterization of advanced structures. In Biophotonics in Point-of-Care III (Vol. 13008, pp. 31-36). SPIE.
Acoustic
With the advancement of Lab-on-Fiber (LOF) technology, it is now feasible to fabricate complex micro- and nanostructures directly on optical fiber tips, paving the way for a new class of optical fiber-based sensors. These innovative structures enhance functionality and sensitivity, particularly for compact, high-resolution sensing solutions. In this context, relying on our group experience with LOF, we are investigating advanced micro-nano structures to optimize ultrasound sensing. The research focuses on the evaluation of various structures to improve the sensitivity and bandwidth of fiber-based acoustic detectors. We are also considering the signal generation aspect, exploring how these configurations can optimize the photoacoustic signal to enhance overall detection performance in ultrasound sensing applications.
[1] Cutolo, M. A., & Breglio, G. (2022). Interferometric Fabry-Perot sensors for ultrasound detection on the tip of an optical fiber. Results in Optics, 6, 100209.
[2] Rossi, B., Aiello, P. M., Cutolo, M. A., Giaquinto, M., Cusano, A., Breglio, G., & Cutolo, A. ‘Polymer-Based Lab-on-Tip Microstructures For Ultrasound Medical Diagnostics’. In 2024 IEEE Sensors Applications Symposium (SAS) (pp. 1-6). IEEE.
Fiber optic sensors
The typical fiber optic sensor is characterized by low weight, reduced dimension, immunity to electromagnetic interferences, robustness in harsh environments (as in presence of ionizing radiation) and others. Among different kinds of fiber optic sensors the Fiber Bragg Grating sensor is widely employed since many decades, taking advantage of the mentioned peculiarities also with the possibility to design a large number of sensors along the same optical fiber, in such a way to obtain an array set up of multiple measurement points. Within the OptoPowerLab, researchers focuses on the employment of fiber Bragg grating sensor for the monitoring of physical phenomenon in harsh conditions. It’s worth to mention the collaboration with Leonardo S.p.A., which led to the usage of fiber Bragg grating sensors for the monitoring of resin arrival during the carbon fiber fabrication process [1]; as well as the temperature monitoring of a sensorized leading edge section for the development of an anti-ice system [2].
[1] Marrazzo, V. R. et al., “Liquid Resin Infusion Process Validation through Fiber Optic Sensor Technology,” Sensors, vol. 22, no. 2, 2022, doi: 10.3390/s22020508.
[2] Marrazzo, V. R. et al., “Study and Validation of an Electrical Anti-Ice Integrated System for Carbon Fiber Leading Edge Airplane Wing Section,” IEEE Trans. Instrum. Meas., vol. 73, pp. 1–9, 2024, doi: 10.1109/TIM.2024.3385032.
optoelectronic systems
To design a sensor network based on fiber optic sensors, an optoelectronic system (called the interrogation system) is needed as a read-out circuit. Its purpose is to convert wavelength shifts from the sensors into digital outputs representing specific physical quantities. However, due to its complexity, the interrogation system often poses challenges in the use of fiber optic sensors, though its application is highly recommended.
Within the framework of the OptoPowerLab, one research focus is the design, characterization, and field testing of custom interrogators aimed at achieving specialized capabilities that commercial systems lack. As demonstrated in the literature and in numerous international projects, interrogation systems with innovative detection algorithms have been developed and tested for high-speed measurement applications [1]. Additionally, in response to the growing use of IoT protocols, an interrogation system was prototyped in collaboration with NEXT Ingegneria dei Sistemi S.p.A. This system operates as an IoT node, directly publishing data without requiring a computer for reading or setting parameters [2].
Finally, in an international collaboration with CERN, a fully analog interrogation system was developed to enhance safety management, avoiding any digital section to increase the overall robustness. This system is embedded into safety frameworks, enabling the fiber optic sensors to be utilized in industrial and safety scenarios, with outputs directly connected to one or more alarm switches [3,4].
[1] Marrazzo, V. R. et al., “Multichannel approach for arrayed waveguide grating‐based fbg interrogation systems,” Sensors, vol. 21, no. 18, pp. 1–17, 2021, doi: 10.3390/s21186214.
[2] Marrazzo, V. R. et al., “IoT Node Interrogation System for Fiber Bragg Grating Sensors: Design, Characterization and On-Field Test,” IEEE Trans. Instrum. Meas., 2024, doi: 10.1109/TIM.2024.3368488.
[3] Marrazzo, V. R. et al., “Experimental Tests of a Full Analog Fiber Optic Monitoring System Suitable for Safety Application at CERN,” IEEE Trans. Instrum. Meas., vol. 72, 2023, doi: 10.1109/TIM.2023.3250283.
