Time‐Resolved Nonlinear Diffuse Femtosecond‐Pulse Reflectometry Using Lithium Niobate Nanoparticles with Two Pulses of Different Colors

Time‐resolved nonlinear optical sum‐frequency generation (SFG) of two differently colored, infrared (sub‐)picosecond laser pulses is studied by means of nonlinear diffuse femtosecond‐pulse reflectometry using lithium niobate nanoparticle pellets. The visible SFG emission exhibits an asymmetric pulse shape in the time domain which is explained within the framework of light propagation in random media. The analysis of the spectro‐temporal data set indicates that LiNbO3 nanoparticle pellets can be used for an alternative type of an optical correlator, e.g., for the determination of a pulse's chirp parameter. This finding is generalized by means of numerical simulations. As a result, ultrashort pulse shapes can now be predicted inside nanoscaled, densely packed media with a nonlinear optical response on a comprehensive basis, giving rise to a number of prospective fields of applications.