Multi-photon microscopy based on resonant four-wave mixing of colloidal quantum dots

摘要

We demonstrate a novel multi-photon imaging modality based on the detection of four-wave mixing (FWM) from colloidal nanoparticles. Four-wave mixing is a third-order signal which can be excited and detected in resonance with the ground-state excitonic transition of CdSe/ZnS quantum dots. The coherent FWM signal is detected interferometrically to reject incoherent backgrounds for improved image contrast compared to fluorescence methods. We measure transversal and axial resolutions of 140 nm and 590 nm respectively, significantly beating the one-photon diffraction limit. We also demonstrate optical imaging of quantum-dot-labeled Golgi structures of HepG2 cells.