| Summary: | 博士 === 國立交通大學 === 光電工程所 === 87 === Two chemical etching techniques have been developed for fabricating scanning near-field optical microscopy (SNOM) probes. These probes have two tapered regions that can be reproducibly constructed with a wide range of cone angles. Our methods can be applied to commercial silica glass fibers. The demonstrated in-plane resolution was estimated to be about 250 nm which is mainly limited by the diameter of the metal-coated tip. The transmission efficiency is better than 10-4.
We propose and demonstrate a novel non-optical technique for regulation of tip-sample distance in a near-field scanning optical microscope (NSOM). The fiber tip for the NSOM is attached to one prong of a quartz tuning fork. The fork is dithered with a gated sinusoidal signal. The vibration of the freely oscillating fiber tip, which manifests as the induced piezoelectric voltage on the fork electrodes, is monitored during the half-period of the gated sinusoid for which the fork is not driven. The time-multiplexing scheme thus allows the tuning fork to serve as a dither and a sensor with high Q-factor simultaneously. The gating technique could also potentially allow the SNOM be used for the investigation of surface relaxation dynamics with high spatial resolution and sub-millisecond time resolution.
We design and calibrate the tube scanner of our home-made NSOM with the lateral deflection about 50mm (in x, y direction), and the longitudinal displacement (in z direction ) is about 10mm. The control program of our NSOM system was developed successfully. This program is based on DOS system.
In order to characterize the image-taking capability of our NSOM, we acquire near-field optical images of a compact mono-layer of polystyrene spheres with a diameter of 2 mm as example. We have also investigated the characteristics of some optical components by using NSOM, such as single-mode optical fiber, and vertical-cavity surface-emitting laser diode (VCSEL).
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