Mechanical resonators can serve as highly sensitive, on-chip thermometers. Leveraging their exceptional frequency stability, we use them as thermal photodetectors across an ultrabroad spectral range, from sub-THz radiation to ultraviolet light. After demonstrating the concept with a single resonator [1], we extended the platform to matrix arrays comprising hundreds of pixels with fully electrical control [2]. By exploiting mechanical nonlinearities, we are now pushing their sensitivity towards the intrinsic thermal-fluctuation limit [3]. Our next goal is to validate this technology in real-world applications, particularly for the early detection of melanoma and other skin diseases within the THz-Skin project.

[1] L. Vicarelli, A. Tredicucci and A. Pitanti, Micromechanical bolometers for subterahertz detection at room temperature, ACS Photonics 9, 360 (2022)
[2] https://phase2.attract-eu.com/projects/h-cube/
[3] L. Alborghetti, B. Bertoni, L. Vicarelli, S. Zanotto, S. Roddaro, A. Tredicucci, M. Cautero, L. Gregorat, G. Cautero, M. Cojocari, G. Fedorov, P. Kuzhir and A. Pitanti, Enhanced sensitivity of sub-THz thermomechanical bolometers exploiting vibrational nonlinearity, ACS Photonics 13, 58 (2026)

Photonic technologies provide a powerful platform for advanced classical and quantum systems. Most devices, however, exploit only a subset of the available degrees of freedom. In addition to amplitude and phase, light carries spin angular momentum through its polarization and can carry orbital angular momentum in suitably structured beams. Achieving complete control of these properties in optomechanical systems requires careful engineering of optical and mechanical mode symmetries. Chiral metasurfaces already enable static polarization control [1]; coupling them to mechanical resonators opens new routes towards fast modulators and polarimeters [2]. Acoustic vortices generated with bulk and surface acoustic waves provide a complementary approach to ultrafast angular-momentum control [3].

[1] S. Zanotto, G. Mazzamuto, F. Riboli, G. Biasiol, G. C. La Rocca, A. Tredicucci and A. Pitanti, Photonic bands, superchirality, and inverse design of a chiral minimal metasurface, Nanophotonics (2019)
[2] S. Zanotto, A. Tredicucci, D. Navarro-Urrios, M. Cecchini, G. Biasiol, D. Mencarelli, L. Pierantoni and A. Pitanti, Optomechanics of dielectric chiral metasurfaces, Adv. Opt. Mat. (2020)
[3] A. Pitanti, N. Ashurbekov, I. de Pedro-Embid, M. Msall and P. V. Santos, GHz acousto-optic angular momentum with tunable topological charge, Nat. Commun. (2022)

At the micro- and nanoscale, patterned structures can be designed as artificial mechanical materials whose elastic properties and wave response go beyond those found in conventional solids. We use this approach to engineer both localized resonances and propagating acoustic waves. Asymmetric nanopatterning of silicon nitride membranes creates an effective orthotropic elasticity, lifting the degeneracy of mechanical modes and allowing their orientation and frequency splitting to be controlled by design [1]. In GaAs phononic metamaterials, asymmetric unit cells reshape the Bloch-mode isofrequency contours and enable both asymmetric and negative refraction of mechanical waves at GHz frequencies [2]. These concepts provide versatile tools for on-chip phonon routing, mode engineering and the development of advanced mechanical sensors.

[1] G. Conte, L. Vicarelli, S. Zanotto and A. Pitanti, Mechanical Mode Engineering with Orthotropic Metamaterial Membranes, Adv. Mater. Technol. 7, 2200337 (2022)
[2] S. Zanotto, G. Biasiol, P. V. Santos and A. Pitanti, Metamaterial-enabled asymmetric negative refraction of GHz mechanical waves, Nat. Commun. 13, 5939 (2022)

Strain is a powerful means of tailoring the electronic and optical properties of two-dimensional materials, but producing controlled strain profiles at the micrometre scale remains challenging. We develop polymeric micro-actuators that are patterned directly on 2D heterostructures and activated by electron-beam irradiation. A quantitative characterization of irradiated PMMA relates electron dose to shrinkage, stress and effective elastic response, providing the mechanical basis for predictable actuator design [1]. Applied to monolayer WS₂ on graphene, paired actuators generate localized uniaxial tensile strain without suspended structures and produce a spatially controlled shift of the excitonic photoluminescence energy [2]. This approach offers a route to programmable strain landscapes for controlling excitons, band structures and charge transport in van der Waals materials.

[1] D. Giambastiani, F. Dispinzeri, F. Colangelo, S. Forti, C. Coletti, A. Tredicucci, A. Pitanti and S. Roddaro, Stress-strain in electron-beam activated polymeric micro-actuators, J. Appl. Phys. 128, 115104 (2020)
[2] F. Colangelo, A. Morandi, S. Forti, F. Fabbri, C. Coletti, F. Viola Di Girolamo, A. Di Lieto, M. Tonelli, A. Tredicucci, A. Pitanti and S. Roddaro, Local tuning of WS₂ photoluminescence using polymeric micro-actuators in a monolithic van der Waals heterostructure, Appl. Phys. Lett. 115, 183101 (2019)