Direct measurement of propagation constant in optical waveguides by heterodyne scattering detection (HSD) method

A new measurement method for the propagation constant of optical waveguides, which can measure the phase difference of two distant points nondestructively, was proposed and demonstrated. A super-fine fiber probe for the photon STM is used to pick up the scattered light from an optical waveguide, and the collected light is detected using a heterodyne technique. The phase difference between two points is measured from the phase change of the electrical signal of heterodyne detection as the fiber probe traces the waveguide pattern. The phase difference between 100 μm distant points in a three-dimensional ARROW was successfully measured and the error was evaluated to be 0.25% by comparison with the theoretical value.