Broadband Multiphoton Microscopy for Nonlinear Spectroscopy of Harmonic Nanoparticles

Thanks to advancements in tunable femtosecond laser sources, broadband nonlinear spectroscopy has become a popular technique for characterizing the nonlinear optical response of various nanomaterials such as 2D nanosheets [1], plasmonic nanostructures [2], Mie resonators [3] and oxide nanoparticles [4]. However, quantitative nonlinear spectroscopy at the single nano-object level is a challenging task, requiring further experimental developments and the establishment of a precise calibration protocol. Here, we have investigated Harmonic NanoParticles (HNPs), namely noncentrosymmetric, polar oxide nanocrystals like BaTiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> or LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> which can be used as new optical nanoprobes for bioimaging [5].