Shape-dependent two-photon absorption in semiconductor nanocrystals.
We report our theoretical investigation onto the shape dependence of two-photon absorption (TPA) in semiconductor nanocrystals (NCs). Based on a four-band model under effective mass approximation, we have developed a simple analytical theory capable of providing a quantitative explanation of the recent TPA measurement on CdS nanorods [Appl. Phys. Lett. 94, 103117 (2009)]. With this theory, we have systematically revealed the characteristics of TPA in CdSe and ZnO NCs with four different shapes: sphere, cube, cylinder and cuboid. Due to the splitting of degenerate energy levels caused by the decreased degree of symmetry, nanocuboids and nanocubes exhibit greater TPA cross-sections than nanocylinders and nanospheres of similar sizes, respectively. Similarly, nanocuboids and nanocylinders possess larger TPA cross-sections than nanocubes and nanospheres of similar lateral dimension, respectively. Given TPA-allowed transitions, nanocuboids show stronger size dependence than nanocylinders. The size dependence of TPA cross-section is more sensitive to the lateral size than the longitudinal size in the cases of nanocylinders and nanocuboids.
Feng
Xiaobo
X
Department of Physics, National University of Singapore, Singapore 117542, Republic of Singapore.
Ji
Wei
W
D000042:Absorption; D000465:Algorithms; D019187:Cadmium Compounds / Q000737:chemistry*; D015233:Models, Statistical; D054118:Nanospheres / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D055095:Optics and Photonics; D010777:Photochemistry / Q000379:methods; D017785:Photons; D045663:Quantum Dots; D013440:Sulfides / Q000737:chemistry*
D019187:Cadmium Compounds; D013440:Sulfides; C034939:cadmium sulfide