One of the most pursued challenges in electronics is the realisation of faster and more efficient transistors to compensate the overgrowing demand for higher computational speed and fast communication channels. Optics has already shown to overcome electronics for long distance communication and it is increasingly acquiring a leading role also in signal communications within the CPU.
The main objective of the project ElecOPteR is the study of a new generation of optical devices that could process signals similarly to present processors but without being affected by the high dissipation of purely electronic components.
At the basis of the system proposed in this project are new quasiparticles called polaritons, that appear in semiconductors when a state of light (photons) and matter (electron-hole pairs, or excitons) couples strongly, combining antagonist properties of the two original particles, such as high coherence and strong interactions.
In order to fabricate a proof-of-concept electro-optical device working at room temperature and based on polariton nonlinearities we studied different materials and selected the best material in terms of nonlinear response, ease of integration and able to show strong light-matter coupling even at room temperature. Therefore we focused on organic–inorganic perovskites, a class of semiconductors that have recently attracted great attentions driven by exceptional progress in photovoltaics, photonics, and optoelectronics. In particular, two-dimensional (2D) perovskites have a quantum-well structure consisting of sub-nanometric inorganic layers (metal halides) confined between organic layers (long chain ammonium cations). This peculiar structure is essential in the nonlinear response of the material. We synthesized large, high-quality single crystals in order to obtain minimum roughness and disorder in the active layer with reduced defects and attenuated non-radiative recombination.
On these semiconductors we observed that the strong light-matter coupling regime was achieved at room temperature with no need to embed them in an optical cavity formed by highly reflecting mirrors. This unexpected result opens new routes to the realization of polaritonic devices working at room temperature because it could allow an easy fabrication, avoiding complex processes.
Furthermore, by embedding the 2D perovskite single crystal in a planar microcavity, we observed highly interacting polaritons with an excitonic interaction constant of gexc = 3 μeV μm2, the highest value measured at room temperature so far.
We implemented 2D perovskite in different polariton electro-optical devices on which we performed several measurements in order to observe mode shifting when an electric field is applied to the device. Although the electrical response of such structures is still under study, some encouraging effects due to mode shifting were observed for high fields opening new opportunities for the application as electro optical routers.
In order to provide an impact also on the socio-economic ground, a thorough study of the scientific and patent literature has been undertaken to assess patentability and freedom-to operate. Even if the patent filing activity in the field of polaritonic devices of some of the biggest electronic companies of the world is not negligible, an IPR strategy has been duly defined to claim the proprietary aspects of the ELECOPTER technology as soon as some of its key features will be finally demonstrated.
