| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 95 === A new method of polarization-modulation (PM) near-field optical microscopy (NSOM) with birefringence measurement is described. In this research, common path heterodyne interferometer and genetic algorithm are combined with the NSOM to establish nanometer scale polarimetric measurement instruments. The birefringence and the diattenuation in the probe are severe problems for PM-NSOM. They will destroy polarization state of the incident light, and make signals demodulation very difficult. In comparison to previous measurement methods, this developed scheme applies genetic algorithm to help polarization controller compensate the birefringence in the fiber and to determine the diattenuation in the probe tip. On the other hand, the intensity-demodulation system which other schemes use is perturbed by surrounding disturbance easily. This system measures phase instead of intensity, so we can quantitatively measure the birefringence and the optical axis of birefrigent materials such as quarter-waveplate without influence of the intensity variation in nano-scale area.
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