We report on a new method of achieving and optimizing a high Q factor in a near-field scanning optical microscope (NSOM) by introducing two nodal wedges to a tuning-fork/fiber probe distance sensor and by selecting a vibrational mode of the dithering sensor. The effect of the nodal wedges on the dynamical properties of the sensor is theoretically analyzed and experimentally confirmed. The optimization achieved by the proposed method is understood from the vibration isolation and the subsequent formation of a local vibration cavity. The optimal condition is found to be less susceptible to the variation of the fiber tip length. This method allows effective NSOM measurement of samples placed even in aqueous solution.

In this study, the internal structure of an optical waveguide embedded in a flexible optical circuit board is observed with a confocal microscope. In order to increase the light reflection from an internal material interface with a very small index difference, and thus enhance the signal contrast, a theta microscopy scheme has been integrated into a conventional confocal microscope, and a high NA oil-immersion lens has been used. The interface reflectivity is increased from roughly 0.0015% to 0.025% by the proposed method, and the internal structure can thus be successfully measured.

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