Second-Harmonic Generation in Aggregates of Lithium Niobate Particles Formed upon Suspension Freezing

This paper demonstrates a significant increase in the efficiency of second-harmonic generation in a suspension of lithium niobate (LiNbO3) particles during freezing at nano and picosecond pum pulse durations. The amplification is caused by the formation of close-packed structures during the solidification process. The energy dependences of the second-harmonic generation, the angular distributions of the scattering intensity, conversion coefficients and the scattering regime in a suspension and in other lithium niobate particle-based samples are studied. This effect can be used for phase transition sensing in a medium, visualization of the particle organization process in ice-templating, and significantly increasing the efficiency of other nonlinear effects in particle matter.