Copper-based thiospinel quantum dots as potential candidates for nonlinear optical applications

Development of new materials such as CuNiCoS4, CuCo5S8, CuCo2S4 are some important candidates which have potential nonlinear optical applications in photonics such as multiphoton spectroscopy/microscopy, laser technology etc. In this study, ternary and quaternary structured group members CuNiCoS4, CuCo5S8, CuCo2S4 quantum dots (QDs) were synthesized experimentally using hot-injection method and investigated theoretically. The theoretical investigations based on Density Functional Theory (DFT) were revealed the electronic and lattice dynamical properties of these materials. The electronic band gaps obtained with DFT calculations were consistent with the band gaps that were obtained from the optical measurements. Nonlinear optical properties of CuNiCoS4, CuCo5S8 and CuCo2S4 in same molarities were examined using femtosecond z-scan method using the laser beam at 800 nm wavelength with different laser intensities. Two photon absorption coefficients and nonlinear refractive indexes were calculated about 10-11 cm/W and 10-16 cm2/W, respectively. Ti-Sapphire femtosecond laser z-scan was also employed to determine the third order nonlinear optical susceptibilities (χ (3)) of each sample and as a result; χ(3) of QDs was found about 10-10 esu.