Second harmonic generation in colloidal solution of heterostructured CdSe/CdS quantum wells

In this work, the second harmonic generation was investigated in colloidal solution of CdSe nanoplatelets with two and three monolayers of CdS shell in the case of the two-photon laser excitation of the light-hole – electron transition (1lh-e). In addition to the two-photon photoluminescence spectrum a narrow spectral peak was observed at the wavelength of the laser’s second harmonic radiation, which intensity increases quadratically with incident laser intensity growth taking into account linear absorption of colloidal solution. Also the cause of the second harmonic generation in CdSe/CdS nanoplatelets was considered and explained. It was suggested that the second harmonic in CdSe/CdS colloidal solution is mostly generated by surface atoms for the part of the nanoplatelets satisfying to phase matching condition of the fundamental and second harmonic waves. The concentration of CdSe/CdS nanoplatelets in colloidal solution at which the second harmonic generation can be observed was determined.