NSOM-based characterization method applicable to optical channel waveguide with a solid-state cladding

A new characterization method employing near-field scanning optical microscope (NSOM) is proposed to measure the propagation characteristics of an optical channel waveguide having a solid-state cladding. For the measurement, the cladding material is replaced with the liquid having the same refractive index as that of the removed cladding. Replacing the solid-state cladding with the liquid enables the NSOM probe to reach the core-cladding interface without changing the boundary condition at the interface. The height of the probe immersed into the viscous liquid is done with the information from the surface profile of the naked core. The measured propagation characteristic shows a good agreement with the simulation result.