<title>Optimization of passive and active fiber probe of scanning near-field optical microscopy</title>

Abstract

For the passive fiber probe, the dependence of the probes' transmission efficiencies on the parameters such as fiber probe shape, taper length, tip diameter and incident wavelength are analyzed with the coupled local-mode theory. It shows that the transmission efficiency of a parabolic fiber probe is about an order of magnitude higher than that of the conical fiber probe. With the increase of the incident wavelength, the transmission efficiency of fiber probes decrease. The images of phase grating by conical fiber probe and by parabolic fiber probe are compared. The Nd:YVO<SUB>4</SUB> frequency-doubling laser with a miniature structure is used as light source in the experiment of SNOM, which provides higher transmission efficiency and make it fascinating in some SNOM's applications. As for active fiber probe, the ASE fiber probe is proposed. It has a wide spectrum of 6nm and may greatly reduce the coherent noise in SNOM image. It may improve the output photon flux several times higher than that of passive fiber probe. Meanwhile, the guide-wave reflection properties in fiber taper are investigated.