A model based on geometrical construction in designing a pencil-shaped fiber probe for near-field optics

We propose a model based on geometrical considerations to determine the etching times required in fabricating a pencil-shaped fiber probe. In this model, we introduce a minimum etching time which is defined as the time required for having a zero apex diameter. Based on its value, the total etching times required in fabricating the pencil-shaped probe could be determined. We have found that the theoretically determined minimum etching time of 2.1 min agrees very well with our experimental value of 2 min.