Resonant and Nonresonant Nonlinear Optical Spectroscopy of CDSE Quantum Dots for Nonlinear Photonic Applications

摘要

The cubic nonlinearity of semiconductor quantum dots with resonant (1h 2e) and nonresonant excitations was investigated with Z-scan and four-wave mixing (FWM) spectroscopy. Z-scan spectroscopy revealed positive nonlinear absorption and negative nonlinear refraction of CdSe quantum dots. The hyperpolarizability of the quantum dots with resonant degenerative FWM was almost two-orders higher than that with nonresonant excitation. The possible physical origins of the cubic nonlinearity of the quantum dots were dominant two-step resonant absorption with resonant excitation and multiple nonlinear processes including a large contribution of the electronic polarization process with both resonant and nonresonant excitations.