arXiv subjects

Luigi Santamaria

Publications and source records attributed to Luigi Santamaria.

3 recordsLinked to original sources

arXiv2023

Spatial-mode-demultiplexing for enhanced intensity and distance measurement

Spatial-mode demultiplexing (SPADE) has recently been adopted to measure the separation in the transverse plane between two incoherent point-like sources. It has been argued that this approach may yield extraordinary performances in the photon-counting regime. Here, we explore SPADE as a tool for precision measurements in the regime of bright, incoherent sources. First we analyse the general problem of estimating the second moments of the source's intensity distribution, for an extended incoherent source of any shape. Second, we present an experimental application of SPADE to the case of two point-like, bright sources. We demonstrate the use of this setup for the estimation of the transverse separation and for the estimation of their relative intensity.

physics.optics↗

arXiv2015

Frequency comb generation in quadratic nonlinear media

We experimentally demonstrate and theoretically explain the onset of optical frequency combs in a simple cavity-enhanced second-harmonic-generation system, exploiting second-order nonlinear interactions. Two combs are simultaneously generated around the fundamental pump frequency, with a spectral bandwidth up to about 10 nm, and its second harmonic. We observe different regimes of generation, depending on the phase-matching condition for second-harmonic-generation. Moreover, we develop an elemental model which provides a deep physical insight into the observed dynamics. Despite the different underlying physical mechanism, the proposed model is remarkably similar to the description of third-order effects in microresonators, revealing a potential variety of new effects to be explored and laying the groundwork for a novel class of highly efficient and versatile frequency comb synthesizers based on second-order nonlinear materials.

physics.optics↗

arXiv2013

Contact-free probing of interfacial charging and Debye-like charge screening in SiO$_2$/PDI8-CN$_2$ systems by optical second harmonic generation

Investigation of the interfacial electronic properties of N,N'-bis(n-octyl)-(1,7&1,6)-dicyanoperylene-3,4:9,10-bisdicarboximide (PDI8-CN2) organic semiconductor films grown on silicon dioxide is performed by polarization-resolved second harmonic generation optical spectroscopy, pointing out a spatial region where charge carriers distribution in the semiconductor lacks inversion symmetry. By developing a model for nonlinear susceptibility in the framework of Debye-Huckel screening theory, we show that the experimental findings can be interpreted as resulting from the presence of a net charge localized at the silicon dioxide, accompanied by a non-uniform charge distribution in the organic semiconductor. Photoluminescence analysis further reinforces this scenario. Reduction-oxidation reactions involving PDI8-CN2 and water molecules are invoked as physical origin of the localized charge. The work outlines a sensitive tool to probe the total charge localized at buried semiconductor/dielectric interfaces in organic thin-film transistors without resorting to invasive contact-based analyses.

cond-mat.mtrl-sci↗