Abstract-Nonlinear TeraHertz Transmission by Liquid Water at 1 THz

Fabio Novelli, Chun Yu Ma,Nidhi Adhlakha,Ellen M. Adams,Thorsten Ockelmann ,Debasish Das Mahanta,Paola Di Pietro, Andrea Perucchi, Martina Havenith

https://www.mdpi.com/2076-3417/10/15/5290

The solvation properties of liquid water originate from the transient network of hydrogen-bonded molecules. In order to probe the coupling between the different modes of this network, nonlinear terahertz (THz) spectroscopy techniques are required. Ideally, these techniques should use a minimal volume and capitalize on sensitive field-resolved detection. Here we performed open aperture z-scan transmission experiments on static liquid cells, and detect the THz fields with electro-optical techniques. We show that it is possible to quantify the nonlinear response of liquid water at ~1 THz even when large signals originate from the sample holder windows

Abstract-Strong nonlinear terahertz response induced by Dirac surface states in Bi2Se3 Topological Insulator

Flavio Giorgianni, Enrica Chiadroni, Andrea Rovere, Mariangela Cestelli-Guidi, Andrea Perucchi, Marco Bellaveglia, Michele Castellano, Domenico Di Giovenale, Giampiero Di Pirro, Massimo Ferrario, Riccardo Pompili, Cristina Vaccarezza, Fabio Villa, Alessandro Cianchi, Andrea Mostacci, Massimo Petrarca, Matthew Brahlek, Nikesh Koirala, Sean Oh, Stefano Lupi

https://arxiv.org/abs/1805.03200

Electrons with a linear energy/momentum dispersion are called massless Dirac electrons and represent the low-energy excitations in exotic materials like Graphene and Topological Insulators (TIs). Dirac electrons are characterized by notable properties like a high mobility, a tunable density and, in TIs, a protection against backscattering through the spin-momentum looking mechanism. All those properties make Graphene and TIs appealling for plasmonics applications. However, Dirac electrons are expected to present also a strong nonlinear optical behavior. This should mirror in phenomena like electromagnetic induced transparency (EIT) and harmonic generation. Here, we demonstrate that in Bi2Se3 Topological Insulator, an EIT is achieved under the application of a strong terahertz (THz) electric field. This effect, concomitant determined by harmonic generation and charge-mobility reduction, is exclusively related to the presence of Dirac electron at the surface of Bi2Se_3, and opens the road towards tunable THz nonlinear optical devices based on Topological Insulator materials.

Abstract-Reshaping the phonon energy landscape of nanocrystals inside a terahertz plasmonic nanocavity

Xin Jin, Andrea Cerea, Gabriele C. Messina, Andrea Rovere, Riccardo Piccoli, Francesco De Donato, Francisco Palazon, Andrea Perucchi, Paola Di Pietro, Roberto Morandotti, Stefano Lupi, Francesco De Angelis, Mirko Prato, Andrea Toma,  Luca Razzari

https://www.nature.com/articles/s41467-018-03120-3

Phonons (quanta of collective vibrations) are a major source of energy dissipation and drive some of the most relevant properties of materials. In nanotechnology, phonons severely affect light emission and charge transport of nanodevices. While the phonon response is conventionally considered an inherent property of a nanomaterial, here we show that the dipole-active phonon resonance of semiconducting (CdS) nanocrystals can be drastically reshaped inside a terahertz plasmonic nanocavity, via the phonon strong coupling with the cavity vacuum electric field. Such quantum zero-point field can indeed reach extreme values in a plasmonic nanocavity, thanks to a mode volume well below λ3/107. Through Raman measurements, we find that the nanocrystals within a nanocavity exhibit two new “hybridized” phonon peaks, whose spectral separation increases with the number of nanocrystals. Our findings open exciting perspectives for engineering the optical phonon response of functional nanomaterials and for implementing a novel platform for nanoscale quantum optomechanics

Abstract-Strong nonlinear terahertz response induced by Dirac surface states in Bi2Se3 topological insulator

• Flavio Giorgianni,
• Enrica Chiadroni,
• Andrea Rovere,
• Mariangela Cestelli-Guidi,
• Andrea Perucchi,
• Marco Bellaveglia,
• Michele Castellano,
• Domenico Di Giovenale,
• Giampiero Di Pirro,
• Massimo Ferrario,
• Riccardo Pompili,
• Cristina Vaccarezza,
• Fabio Villa,
• Alessandro Cianchi,
• Andrea Mostacci,
• Massimo Petrarca,
• Matthew Brahlek,
• Nikesh Koirala,
• Seongshik Oh
• & Stefano Lupi

http://www.nature.com/ncomms/2016/160426/ncomms11421/full/ncomms11421.html

Electrons with a linear energy/momentum dispersion are called massless Dirac electrons and represent the low-energy excitations in exotic materials such as graphene and topological insulators. Dirac electrons are characterized by notable properties such as a high mobility, a tunable density and, in topological insulators, a protection against backscattering through the spin–momentum locking mechanism. All those properties make graphene and topological insulators appealing for plasmonics applications. However, Dirac electrons are expected to present also a strong nonlinear optical behaviour. This should mirror in phenomena such as electromagnetic-induced transparency and harmonic generation. Here we demonstrate that in Bi2Se3 topological insulator, an electromagnetic-induced transparency is achieved under the application of a strong terahertz electric field. This effect, concomitantly determined by harmonic generation and charge-mobility reduction, is exclusively related to the presence of Dirac electron at the surface of Bi2Se3, and opens the road towards tunable terahertz nonlinear optical devices based on topological insulator materials

Abstract-Terahertz Absorption of illuminated Photosynthetic Reaction Center solution: a signature of photoactivation?

Ida Veronica Lundholm,   Weixiao Yuan Wahlgren,  Federica Piccirilli,   Paola di Pietro,   Annette Duelli,  Oskar Berntsson,   Stefano Lupi,   Andrea Perucchi and  Gergely Katona  

RSC Adv., 2014, Accepted Manuscript

DOI: 10.1039/C4RA03787A
Accepted 27 May 2014
First published online 29 May 2014

http://pubs.rsc.org/en/content/articlelanding/2014/ra/c4ra03787a#!divAbstract

Photosynthetic reaction centers develop a stable charge separated state upon illumination. To investigate the molecular vibrations associated with the illuminated state of a reaction center we recorded terahertz absorption spectra of the photosynthetic reaction center from Rhodobacter sphaeroides in the dark and upon illumination and observed a small, but significant THz absorption increase in the 20 to 130 cm-1 spectral region. Reaction centers show very similar terahertz absorption increase when solubilized in detergents and in a lipidic sponge phase indicating that the nature of the bulk solvent has limited influence on the vibrational spectrum. The absorption change of the isolated LM subunit is very similar to that of the intact reaction center. Through temperature control experiments we show that 89 % of the absorption change is likely attributed to the non-thermal activation of the protein molecules. These results indicate that picosecond molecular vibrations change primarily in the cofactors and/or in the evolutionary conserved core of the reaction centre upon illumination, whereas the nuclear motions of the H-subunit and the bulk solvent have limited impact on the terahertz spectral changes.