Pilot Study On Fiber-optic Two-photon Microscopy

Two-photon laser scanning microscopy (2PLSM), an optical imaging technique, has been widely applied in the biomedical field. Compared to the traditional microscopies, 2PLSM achieves an effective improvement in the resolution, imaging depth, photobleaching, photo damage etc. As developments in biomedical imaging and the utilization of special types, more and more imaging methods trend to use optical fibers, and also the 2PLSM. Fiber based 2PLSM has not only obtained the advantages of fiber system such as compact, convenient etc, but also can get its performance improved and function updated. In this thesis, with aiming for the fiber 2PLSM, experiments are carried out to study two key issues in process: axial scanning and pulse compression.First, a 2PLSM axial scanning method is developed. By studying the generation of ring patterns, the scanning mechanism is analyzed. Then the feasibility is evaluated through single photon excitation experiment. And the possibility of used in 2PLSM is validated by two photon excitation experiment. Combined with the acousto-optic deflector (AOD), this method can implement fast, inertia-free axial scanning, and reach aμs scanning rate. Meanwhile, the contrast will be enhanced because the focused ring beam generates a dark-field illumination.Second, the experiment of femtosecond pulse compression is studied primarily. The principle of spectral broadening in nonlinear photonic crystal fiber (PCF) is discussed to illuminate the following work. Then fiber coupling is experimented particularly. When the incident laser wavelength is set in the abnormal dispersion region of the PCF (800 nm), supercontinuum generation (530 nm-980 nm)is observed. And in the normal dispersion region, comparative experiments are carried out to study the relationship between spectral broadening and pulse compression. In the end, the scheme of a short nonlinear PCF followed by a grating compressor is tested.The pilot study and experiments of axial scanning and pulse compression in this thesis potentially enhance the functions and widen the applications of 2PLSM.