High spatial resolution diagnostics of optical waveguides using a photon-scanning tunneling microscope

We propose a high-resolution diagnostics technique for optical waveguides using a photon-scanning tunneling microscope (P-STM). This technique has the advantageous capabilities of nondestructive measurement and informative analysis of guided mode. The capability of this technique was evaluated by measuring the characteristics of an LiTaO3waveguide. Scattered light spot of 500-nm diameter caused by defects was measured, and a normalized width was estimated to be 3.7 μm. Moreover, we obtained the power dispersion in Y-branch waveguides, which were in good agreement with the theoretical plots calculated by the beam propagation method (BPM).