Imaging of the optical mode of waveguiding devices by scanning near-field optical microscopy

Scanning optical microscopy with uncoated dielectric silica probe is used in the near field to investigate the propagation of optical modes along tapered integrated semiconductor optical amplifier devices and at larger working distances to study the electromagnetic intensity profile in the focal plane of various microlensed fibers. We show how this technique provides images of the mode structure of optoelectronic devices and profiled optical fibers with typical sizes in the range 2-10 μm, with an accuracy of 0.2 μm in beamwaist measurements.