Second harmonic generation in colloidal CdSe/CdS nanoplatelets

In this Letter, we report the second harmonic generation (SHG) in a colloidal solution of CdSe/CdS nanoplatelets (NPLs) in the case of two-photon excitation in the region of exciton transition from the light holes sub-band to the conduction sub-band (549 nm, 1lh-1e) by femtosecond laser pulses (1064 nm, 100 kHz). Discovery of the SHG in colloidal solutions of NPLs opens up new perspectives for their use as biomarkers or for optical imaging, since in contrast to two-photon photoluminescence the SHG can increase both spectral and temporal resolution by several orders of magnitude. The SHG is also extremely important to consider when designing two-photon pumping lasers.