Abstract

Single glass fibers whose diameter-to-wavelength ratio is large, for example, d/λ = 50, strongly focus normally incident laser light to give greatly enhanced intensities both within and in the near field of the fiber, even when the fiber is not at resonance. Calculated results show the dependence of the enhancement on the diameter-to-wavelength ratio and on the fiber index of refraction. Measured results confirm the calculated spatial distribution of the intensity. Even greater enhancements are observed for spherical particles. The near-field intensity for a single fiber is greatly modified when a second fiber is moved into its near field. Calculations of the near-field intensities for two coupled fibers have been made using the addition theorem and the iterative approach of Olaofe.¹ The results provide insight into the coupling mechanism, especially the dependence of the coupling on the fiber separation and on the orientation of the two fibers relative to the incident wave. Measured results for a glass fiber in front of a mirror confirm the major features of the calculated results.

© 1986 Optical Society of America