A facile method to synthesis high-quality CdSe quantum dots for large and tunable nonlinear absorption

The CdSe nanocrystals (NCs) were synthesized by a hot injection method in the atmospheric environment without any protective gas. The size of CdSe NC was tuned by controlling the growth time and the NCs' high-quality was confirmed by UV-visible spectroscopy, photoluminescence spectroscopy, X-ray diffraction and transmission electron microscopy. A large third-order nonlinear optical (NLO) absorption of CdSe NCs was obtained by using Z-scan technique with 30 ps excitation at 532 nm, which was tunable with variable size and the energy difference between the first exciton absorption peak and the laser wavelength. The NLO susceptibility of CdSe NCs can reach as high as 1.81 × 10−10 esu at the size of 3.3 nm and at resonance absorption peak.