STUDY OF OPTICAL-FIBER STRUCTURES BY ATOMIC-FORCE MICROSCOPY

A novel method using atomic force microscopy (AFM) to study optical fi bre structures at the fibre end-face has been successfully developed. The doping concentration profiles of fibres revealed by differential e tching speeds in a saturated solution of ammonium bifluoride at room t emperature (25 degrees C) were obtained from AFM topographic images. T he superior spatial resolution of AFM made it possible to resolve conc entric structures a hundred times smaller than the feature, due to the difference in the known refractive index (Delta n) of 1 x 10(-3). Fib res with small core diameters and anisotropic structures, such as pola rization-maintaining fibres, were studied with ease.