For centuries, the rapid progress of optical microscopy brings us new opportunities to greatly understand the unknown microcosm. The innovation of optical microscopy has been proven to be the impetus for the development of biology and medicine. In the past two decades, the nonlinear optical (NLO) microscopy attracted numerous attentions, due to its unique advantages, including label-free imaging, large penetration depth, inherent 3-D optical sectioning and less photo-toxicity. In fact, each nonlinear optical microscopy technique (two-photon excitation fluorescence (TPEF), second harmonic generation (SHG), third harmonic generation (THG), and stimulated Raman scattering (SRS)) provides specific imaging contrast for biomedical applications. Therefore, it’s highly desired to combi...[ Read more ]

For centuries, the rapid progress of optical microscopy brings us new opportunities to greatly understand the unknown microcosm. The innovation of optical microscopy has been proven to be the impetus for the development of biology and medicine. In the past two decades, the nonlinear optical (NLO) microscopy attracted numerous attentions, due to its unique advantages, including label-free imaging, large penetration depth, inherent 3-D optical sectioning and less photo-toxicity. In fact, each nonlinear optical microscopy technique (two-photon excitation fluorescence (TPEF), second harmonic generation (SHG), third harmonic generation (THG), and stimulated Raman scattering (SRS)) provides specific imaging contrast for biomedical applications. Therefore, it’s highly desired to combine various NLO techniques to develop a multi-modal NLO microscopy.

In my MPhil study, we firstly constructed a multi-modal NLO system, incorporating diverse functional NLO techniques (SRS, THG, SHG, and TPEF). In this NLO system, the SRS microscopy technique was newly developed, providing fingerprint detection of different chemical bonds. Great effort was devoted to the optimization for the system performance, in terms of shortening the pulse duration of the Stokes light, improving the modulation depth, and precisely achieving co-localization of the pump beam and Stokes beam. Thereafter, we applied this multi-modal NLO system to image mitochondria and lipid metabolism of 3T3 cells and acetowhitening effect of cancer cells. A great deal of important biological information was obtained with the help of all kinds of NLO signals.