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.

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In this paper, we newly propose an optical triplexer which is one of key components in Gigabit Ethernet Passive Optical Network for Fiber-To-The-Home network. Based on a photonic crystal structure with local point defects, two types of optical triplexers were optimally designed. The size-tuned optical triplexer shows the extinction ratios of -17.8 dB, -14.4 dB, and -15.9 dB for the wavelengths of 1310nm, 1490nm, and 1550 nm, respectively. And the index-tuned optical triplexer shows the extinction ratios of -19.24dB, -17.09dB, and -22.68dB for the wavelengths of 1310nm, 1490nm, and 1550 nm, respectively. The size of the proposed optical triplexers were about 4 × 3 µm 2 .

Despite the power of far-field super-resolution microscopies for three-dimensional imaging of biomolecular structures and processes, its application is challenged in dense and crowded samples and for certain surface and membrane studies. Although near-field imaging with its ability to provide intrinsic subdiffraction limited spatial resolution at any optical modality, its application to biological systems has remained limited because of the difficulties of routine operation in liquid environments. Here we demonstrate stable and sensitive near-field scanning optical microscopy (NSOM) in a liquid based on a new mechanical resonance control and an optimization of the tip length, achieving a high quality factor (>2800) force sensing of the near-field probe. Through near-field imaging of the spatial distribution of epidermal growth factor receptors (EGFRs) on the membrane of A431 cancer cells as an example, we reveal nanoscale correlations between surface EGFR and intracellular organelle structures with ∼50 nm spatial resolution. The method provides a new avenue for surface imaging in viscous liquid media to complement super-resolution microscopy for studies of biological membranes, nanostructures, and interfaces.

A resonant shift and a decrease of resonance quality of a tuning fork attached to a conventional fiber optic probe in the vicinity of liquid is monitored systematically while varying the protrusion length and immersion depth of the probe. Stable zones where the resonance modification as a function of immersion depth is minimized are observed. A wet near-field scanning optical microscope (wet-NSOM) is operated for a sample within water by using such a stable zone.