Near-field optical imaging properties by passive and active fiber probes

Passive and active fiber probes, used for the scanning near- field optical microscope, show different image properties. For the passive fiber probe, a better optical image contrast has been obtained with a parabolic taper than with a linear taper. The reflected fields in different fiber tapers have been discussed. For the active fiber probe, an ASE probe made of Er3+-doped fiber has shown a higher efficiency of several times and a lower image noise than the usual passive probe.