A new optimization method to get a smooth freeform optical surface from an initial surface generated by the supporting quadratic method (SQM) is proposed. To smooth the initial surface, a 9-vertex system from the neighbor quadratic surface and the Zernike polynomials are employed to establish a linear equation system. A local optimized surface to the 9-vertex system can be build by solving the equations. Finally, a continuous smooth optimization surface is constructed by stitching the above algorithm on the whole initial surface. The spot corresponding to the optimized surface is no longer discrete pixels but a continuous distribution.
The thermo-optic properties of CdSe/ZnS quantum dots (QDs) are investigated in this paper. Two CdSe/ZnS QDs-doped samples are fabricated and the closed aperture Z-scan data were obtained by a single-beam Z-scan setup with a continuous laser as the exciting source. With the measured curves the coefficient of nonlinear refractive index n2 (caused by thermal effect) and the thermo-optic coefficient were achieved. CdSe/ZnS QDs-doped materials show larger thermooptic coefficients than the glass materials by 2 orders of magnitude.