| Summary: | 碩士 === 國立陽明大學 === 生醫光電研究所 === 100 === Fluorescence detection and lifetime imaging provided crucial information on molecular dynamics, such as the conformation of molecules and the changes of the nano-environment of fluorophores. It has been widely used to characterize various molecular dynamics parameters, for example, fluorescence resonant energy transfer, ion concentration, pH of solvent. However, the detection of fluorescence is critically depending on numerical aperture or the collection solid angle of the condenser due to its incoherent nature. Thus, the setting is usually a microscopy one and the working distance is very limited. In this study, the limitation on working distance is removed by converting the incoherent fluorescence signal into a coherent one through stimulated emission.
We have implemented a pump-probe setup based on stimulated emission to greatly extend the working distance. Nonetheless, the spatial resolution is still dictated by the NA used. We are reporting the successful detection of fluorescence signal from dye (ATTO 647N) by a lens (f=4cm). Delay electronic, instead of mechanical moving stage, is used to control the time delay between the excitation and stimulation pulse lasers so that beam profile distortion and optical misalignment can be avoided. The combination of electro-optical modulator and lock-in amplifier is very effective in detecting the stimulated emission signal, which depends on the population of the fluorophore in the excited stated. We believe numerous applications are waiting to be further explored in the coming future.
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