Nanoscale Imaging by Micro-Cavity Scanning Microscopy

In this work we describe a novel kind of scanning probe microscope carried out through an optical fiber extrinsic micro-cavity. The micro-cavity is realized by approaching a single mode fiber to a sample placed on a piezo-scanner. The distal end of the fiber and the sample realize the optical resonator. The probe is fed by a low-coherence source and the reflected intensity is acquired by an optical spectrum analyzer. The resonant behavior of the cavity enables to overcome the conventional Rayleigh limit. For this system the transverse resolution is not defined by the NA of fiber but it is a function of the transverse electromagnetic field inside the micro-cavity. The lens-free system paves the way towards quantitative measurements in air and liquid environment.