Optical parametric amplification is a second-order nonlinear process whereby an optical signal is amplified by a pump via the generation of an idler field. This mechanism is inherently related to spontaneous parametric down-conversion, which currently constitutes the building block for entangled photon pair generation, a process that is exploited in modern quantum technologies.
An International collaboration between CNR-SPIN (Alessandro Ciattoni), Politecnico di Milano, IFN-CNR, University of L’Aquila and Columbia University has lead to the demonstration of a single-pass optical parametric amplification at the ultimate atomic thickness limits. The outcomes of the theoretical/experimental investigation have been published on Nature Photonics.
Using semiconducting transition metal dichalcogenides, amplification over propagation through a single atomic layer has be attained. Such a second-order nonlinear interaction at the two-dimensional limit bypasses phase-matching requirements and achieves ultrabroad amplification bandwidths. In agreement with first-principle calculations, the amplification process has been shown to be independent of the in-plane polarization of signal and pump fields. By the use of AA-stacked multilayers, a clear pathway towards the scaling of conversion efficiency has been proven. The results pave the way for the development of atom-sized tunable sources of radiation with potential applications in nanophotonics and quantum information technology.
Trovatello, A. Marini, X. Xu, C. Lee, F. Liu, N. Curreli, C. Manzoni, S. Dal Conte, K. Yao, A. Ciattoni, J. Hone, X. Zhu, P. J. Schuck & G. Cerullo, "Optical parametric amplification by monolayer transition metal dichalcogenides", Nature Photonics 15, 6 (2021)