Tuning the nonlinear optical response of atomically thin materials (25/ABR/2022)

Photonics Group Research Seminar

Title: Tuning the nonlinear optical responseof atomically thin materials

Resume: Atomically thin materials have recently attracted a huge interest in the field ofnonlinear optics, thanks to their strong interaction with light, their ease ofintegration on photonic platforms and their ultra-thin nature, which relaxes thephase matching constraints. Applications in this context include frequencyconversion and mixing, ultra-short pulse characterization, generation ofentangled photons, sensing and high-speed logic operations. In this talk, I willsummarize some of our recent results in this field. I will first present differentapproaches to achieve large modulation of the harmonic generation in grapheneand in transition metal dichalcogenides (TMDs). The first method is based on theelectrical control of the graphene’s Fermi energy. This allows to tune the nonlinearmulti-photon resonances occurring within the Dirac cone and thus to achieve alarge electrical modulation of the third harmonic generation. In addition, thirdharmonic generation in graphene can be modulated by Pauli blocking or bytuning the electronic temperature in an all-optical approach. The second exampleregards broadband all-optical modulation of the second harmonic generation.The concept is based on symmetry considerations and thus it is applicable to anymaterial of the D3h symmetry group and with deep sub-wavelength thickness,such as all monolayer TMDs. With this approach we demonstrated a 90° rotationof the second harmonic polarization on a time-scale limited only by thefundamental pulse duration. In addition, this ultrafast polarization switch can beimmediately applied to realize all-optical second harmonic amplitude modulation.Finally, I will present some nonlinear optical devices based on atomically thinmaterials. In particular, I will discuss gas sensing based on electrically tunablefour-wave mixing and tuning of the lasing properties of ZnO nanowires byhybridization with TMDs.

Speaker: Prof. Giancarlo Soavi — Institute of Solid State Physics,
Friedrich Schiller University Jena