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 LiTaO
₃
waveguide. 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).