Giampiero Gerini

Research area

Metamaterials and metasurfaces are artificially engineered structures consisting of arrays of sub-wavelength scatterers embedded or deposited on a host material. While in metamaterials the scatterers alter the host material electrical parameters, realizing values not available in nature, in metasurfaces, the scatterers induce very abrupt variations of the phase, polarization and amplitude of the impinging wave, within a very thin membrane. These unconventional electromagnetic properties can lead to major breakthroughs in sensing, imaging and miniaturization.

In particular, optical metasurfaces allow all possible forms of light manipulation with unconventional, extremely thin optical devices, like: flat lenses, deflectors, polarizers, holograms, perfect absorbers, filters, beam shapers, near-to-far-field transducers. Their extraordinary electromagnetic properties and their extremely thin dimensions allow very high levels of integration with other components and sensors.

My main research goal in this field is to enable the development of novel system/instrument concepts based on metasurfaces/metamaterials. To accomplish this goal, we develop modelling/design frameworks, we build and test demonstrators and we embed these structures in the design of complex systems. TNO has a long and world recognized competence in the development of instruments/systems for space, defence and semiconductor industry. With the use of metasurfaces and metamaterials we are enabling the development of a new generation of instruments.

In this context, my research closely contributes to the TNO roadmaps ‘Semiconductor’, ‘Space’ and ‘Information & Sensor systems’.

Recent results

• Spectro-polarimetric surfaces for the reconstruction of the polarization states of light in multiple spectral bands have been designed and assessed in terms of performances and manufacturing complexity. One concept has been manufactured and validated experimentally. These surfaces, integrated with a pixelated sensor, could be used for the realization of innovative spectro-polarimetric space instruments (e.g. for aerosol concentration measurements in Earth Observation).
• Dielectric metasurfaces have been designed for Surface Enhanced Raman Spectroscopy. The advantages of using dielectric structures, compared to plasmonic ones have been discussed, demonstrating the possibility to achieve same values of enhancement factor, without the disadvantage of ohmic losses inherent of metallic structures. These losses reduce the system efficiency and generate also heat that can modify or damage the analyte under analysis. Furthermore, a model has been developed to quantify the effect of optical trapping achieved in the structure in terms an additional increase of the enhancement factor.
• An array of nano antennas located in proximity of a scattering source can act as near-to-far-field transducer achieving deep sub-wavelength accuracy in the detection of the scattering source position. Experimental measurements have validated the theoretical results. Such concept can provide a powerful metrology system for the semiconductor industry.

PhD supervision

• P. Stoevelaar (TNO ERP 3D Nanomanufacturing)
• R. Buijs (NWO HTSM)
• R. Bijster (TNO ERP 3D Nanomanufacturing)
• P. Gao (China Scholarship Council grant)

Top publications

• T. A. W Wolterink, R. D. Buijs, G. Gerini, A. F. Koenderink and E. Verhagen, "Localizing nanoscale objects using nanophotonic near-field transducers" Nanophotonics, vol.10, no.6, 2021.
• C. F. Kenworthy, L. P. Stoevelaar, A. J. Alexander, G. Gerini, “Using the near field optical trapping effect of a dielectric metasurface to improve SERS enhancement for virus detection”, Nature - Scientific Reports 11, 6873 (2021). .
• R. Buijs, T. Wolterink, G. Gerini, F. Koenderink, and E. Verhagen, “Information advantage from polarization-multiplexed readout of nanophotonic scattering overlay sensors”, Opt. Express 29, 42900 (2021).
• T. Wolterink, R. Buijs, G. Gerini, E. Verhagen, and F. Koenderink, “Calibration-based overlay sensing with minimal-footprint targets”, Appl. Phys. Lett. 119, 111104 (2021).
• T. Wolterink, R. Buijs, G. Gerini, E. Verhagen, and F. Koenderink, “Programming metasurface near-fields for nano-optical sensing”, Adv. Opt. Mater. 9, 2100435 (2021).